PyroSim User Manual

1.1. Introduction

PyroSim is a graphical user interface for the Fire Dynamics Simulator (FDS) version 6.8.0. FDS is closely integrated into PyroSim. FDS models can predict smoke, temperature, carbon monoxide, and other substances during fires. The results of these simulations are used to ensure the safety of buildings before construction, evaluate safety options of existing buildings, reconstruct fires for post-accident investigation, and assist in firefighter training.

FDS is a powerful fire simulator which was developed at the National Institute of Standards and Technology (NIST). FDS simulates fire scenarios using computational fluid dynamics (CFD) optimized for low-speed, thermally-driven flow. This approach is very flexible and can be applied to fires ranging from stove-tops to oil storage tanks. It can also model situations that do not include a fire, such as ventilation in buildings.

The PyroSim interface provides immediate input feedback and ensures the correct format for the FDS input file.

Some highlights include:

In summary, PyroSim helps you quickly and reliably build complex fire models.

1.2. Download and Install

You can download the current version, sign up for a free trial, and purchase the software from the PyroSim Support Page. This page also provides instructions for installation and activation. Troubleshooting info can be found on the PyroSim FAQs page. There is no functional difference between the trial version of PyroSim and the full version, the only limitation is the trial license duration.

Administrator privileges are required to install PyroSim. This is necessary because the installer adds processes to the operating system for license management and parallel FDS simulation. The PyroSim installer will also add Windows Defender exclusions for the bundled FDS executables in order to avoid performance issues related to Windows Security. To see how to do this manually, see Section 1.4.1.

If an older version of PyroSim is present, the installer will automatically remove the older version during the installation process. License files and properties files (e.g., recently opened PSM files) from the older installation will be preserved and utilized by the updated version of PyroSim.

PyroSim will regularly check for and notify the user of available updates to the software when configured to do so. By default, PyroSim will check for updates on startup and display the relevant information in the Check For Updates dialog when one is available.

Users can also access this dialog by navigating to Help→Check For Updates

The dialog can be disabled on startup by unchecking Check for newer version on startup.

1.3. Some Modeling Suggestions

In this section we make some suggestions that can help speed your model development. The big issues most users will face are: selecting a mesh, defining your geometry, selecting a reaction, and defining the correct boundary conditions.

We will broadly discuss each of those topics, but before you start thinking about them please:

1.4. Using a Different FDS Executable

Each PyroSim release comes bundled with FDS. A particular PyroSim release is designed and tested against the bundled version of FDS. You can use PyroSim to run any version of FDS, however PyroSim will generate the input file based on the bundled version of FDS and it is important to understand differences in input format between the FDS versions before changing PyroSim’s FDS version.

To change the version of FDS used by PyroSim:

1.5. Additional FDS and Smokeview Documentation

In preparing this manual, we have liberally used descriptions from the FDS User’s Guide (McGrattan, et al., 2015). Links to the FDS Users Guide, the FDS Technical Reference, and the Smokeview Users Guide are included in PyroSim on the Help menu. You can also download documentation, executables, and verification and validation examples at: https://pages.nist.gov/fds-smv/ .

1.6. Contact Us

Thunderhead Engineering
403 Poyntz Avenue, Suite B
Manhattan, KS 66502-6081
USA

Sales Information: sales@thunderheadeng.com
Product Support: support@thunderheadeng.com
Phone: +1.785.770.8511

2.1. PyroSim Interface

PyroSim provides four editors for your fire model: the 3D View, 2D View, Navigation View, and the Record View. These all represent your current model. If an object is added, removed, or selected in one view, the other views will simultaneously reflect the change.

Each view is briefly described below.

2.2. Navigation View

The navigation view is a tree-like view on the left side of the PyroSim main window. An example of this view in use is shown in Figure 2. When you right-click on an item in this view, a list of the functions PyroSim can perform on that item is shown. To rearrange objects in the Navigation view, make a selection and then drag the object(s) to the new location.

2.3. 3D View

Use the 3D view to rapidly obtain a visual image of the model and perform some drafting. In this view, the user can navigate through the model in 3D and select objects. This view also provides display filters to quickly show/hide entire categories of objects or switch between floors. In addition, any drafting that requires objects to be snapped to faces of other objects, such as drawing a vent on an obstruction or attaching a measuring device to a solid can be easily achieved in this view. For more information on drafting, see Chapter 9.

2.3.2. Navigation/Selection

There are several tools that can be used to navigate the model and select objects. The tools for the 3D view are found in the navigation toolbar above the 3D view as shown in Figure 3.

Select/Manipulate Tool ()

This general-purpose tool can be used to perform most navigation activities.

Selection

The following actions can be used to select items.

• Left-click an object to select it.
• Drag the left mouse button to draw a selection box and select all objects within the box.
• Double-click the left mouse button to select and open a properties dialog for the object under the cursor.
• Hold ALT while performing selection to select the hierarchical parent of the object under the cursor.
• Right-click to show a context menu for selected items under the cursor.

Panning

Drag the middle mouse button to pan the model.

Orbiting

Drag the right mouse button to orbit the model.

Zooming

Roll the scroll wheel on the mouse to zoom in and out of the cursor position.

Manipulating

If a single object is selected, it may show manipulation handles (blue dots or faces). Left-click one of the handles to begin manipulation or drag the left mouse button to perform manipulation in one gesture. For more information on manipulation, see Section 9.16.

Orbit Tool ()

This is another general-purpose tool that is a bit more limited than the Select/Manipulate Tool.

Orbiting

Drag any mouse button to orbit.

Panning

Hold the SHIFT key down while dragging any mouse button to pan.

Zooming

Hold the ALT key down while dragging any mouse button to zoom.

Manipulating

This tool cannot perform manipulation.

Roam Tool ()

This tool allows the user to move into the model rather than viewing it only from the outside as shown in Figure 5. This tool can take some experimentation, but once mastered, it can provide unique views of the model.

Selection

This is the same as with the Orbit Tool.

Looking

Drag any mouse button to look around. This pivots the camera about the camera’s location, similar to a first-person video game.

Moving

There are keyboard shortcuts to modify the mouse actions.

• Hold the ALT key while dragging a mouse button to move the camera up and down along the Z axis.
• Hold the CTRL key while dragging a mouse button to move the camera forward, backward, and side-to-side in the camera’s XY plane.

Pan Tool (), Zoom Tool (), Zoom Box Tool ()

These tools break out the functionality of the above tools so that dragging any mouse button will perform the needed action.

Exterior and Interior Views of a Model

2.3.6. Filtering

There are several ways to filter the objects shown in the 3D view. Filtering can be performed with clipping planes that are associated with floors or through filter buttons that can quickly show/hide categories of objects.

To use clipping, the user must first define floors for the model as discussed in Section 8.5. Once the floors are defined, a floor can be selected by using the Floor Drop-down above the Navigation View as shown in Figure 6.

Once a floor has been selected, its clipping planes will be applied to the entire scene to only show objects within the clipping region.

Filtering can also be performed using the filter toolbar buttons as shown in Figure 7. Selecting/deselecting these buttons will quickly show/hide all objects of a specific type, such as obstructions, holes, vents, etc.

Filtering can also be applied to meshes but in a slightly different way. Instead of showing/hiding all meshes, the user can selectively show/hide three different elements of them using the mesh filter toolbar shown in Figure 8. This toolbar selectively allows viewing mesh grid lines, mesh boundaries, and mesh outlines. Filtering mesh elements shows the different mesh elements. Figure 9 shows the grid lines, Figure 10 shows the boundary, and Figure 11 shows the outline.

Filtering mesh elements

Background images attached to floors can be quickly shown/hidden using the Show Background Image filter button () next to the floor drop-down.

2.4. 2D View

The 2D view is mostly the same as the 3D view with some key differences:

2.5. Record View

The Record View shows an up-to-date display of the FDS input file currently represented by the PyroSim model. This view is divided into two sections, the Model Records and the Additional Records.

2.6. Scenarios

Scenarios can be used to manage variations of a single model. Any time a simulation object is enabled or disabled, that change is retained by only the current scenario. Objects can also be enabled or disabled per scenario via the Enable/Disable Object(s) per Scenario dialog, found in the context menu opened by right-clicking a selected object.

Multiple fire scenarios can be managed using the Scenarios box on the main toolbar. The Edit Scenarios dialog, activated by the toolbar button next to the Scenarios box, can be used to manage scenarios and examine which objects are enabled in a specific scenario.

For models that use multiple scenarios, a bulk export option is available on the File menu in the Export submenu, called Export Scenarios. Using this feature will export an FDS input file (and other supporting files) for each scenario in subfolders where the PSM file has been saved. A BAT file will also be produced that can be double-clicked in Windows Explorer to run all scenarios in sequence.

You can learn more about the scenarios feature by following along with the PyroSim Scenarios Tutorial.

2.7. Snapshots of Display

Images of the current display can be saved to a file by opening the File menu and clicking Screenshot. The user can specify the file name, image type (png, jpg, tif, bmp), and the resolution. A good choice for image type is Portable Network Graphics (png).

2.8. Preferences

PyroSim preferences can be set by going to the File menu and choosing Preferences. Any changes to the preferences will be set for the current PyroSim session and be remembered the next time PyroSim is started. The preferences are split into several groups, including PyroSim, Record View, FDS, Results, and Display preferences.

2.8.1. PyroSim Preferences

These describe global PyroSim preferences as shown in Figure 12.

Format FDS file for easy reading

Controls the format of real numbers in the FDS input file created by PyroSim. When this is checked, a real number is written such that if the absolute value is >=.001 and < 10000, it is written in decimal notation; otherwise, it is written in scientific notation.

Max precision

Controls the number of significant digits written to the input file.

Number of Recent Files

The maximum number of files that will be shown in the File → Recent PyroSim Files or File → Recent FDS Files menus.

Autosave

Instructs PyroSim to periodically create a backup of the current model that is deleted when the PyroSim model is closed. This backup is useful in case PyroSim crashes or the computer loses power. The backup file is stored in the same directory as your PyroSim file. If your working PyroSim file (testing.psm for example) becomes corrupted, then you can find the file that starts with a tilde like ~testing.psm shown in Figure 13. This file is sometimes preferred if you have a crash, as it will be the most up to date version of your work before your crash. If it cannot be opened or results in an immediate crash, there is another backup file described next that is the second best option. The default setting enables this feature and saves every 10 minutes. In some cases, when working with large models, this can cause unexpected delays during the save and some users prefer to disable the feature and save manually.

Create Backup on Open

Controls whether PyroSim makes a backup copy of the PyroSim file after last successfully opening it. This backup remains on disk when the main PyroSim file is closed, and so it can be used in case the main file somehow becomes corrupted. The backup file is stored in the same directory as your PyroSim file. If your working PyroSim file or the automatic backup file becomes corrupted, then you can find the autosave backup file that has a tilde in the file extension, like testing.~sm shown in Figure 13. Rename (recommended) or delete your current working file, then change the file extension on this backup file, changing the tilde in the extension (.~sm) to a p character to get .psm. You can now open the new .psm file as you normally would.

Record Preview

Adds a preview pane to many of the dialogs in PyroSim. This preview pane shows the text that will be produced for the FDS input file. This can be helpful for users that want to understand exactly how PyroSim options correspond to FDS input.

Show Splash Screen on Startup

Controls whether the PyroSim splash screen is shown when starting PyroSim.

Keyboard Shortcuts

Launches a dialog for mapping various PyroSim actions to user specified shortcuts.

2.8.2. Keyboard Shortcuts

The Keyboard Shortcuts dialog is launched from the PyroSim preferences panel. These preferences bind combinations of modifier keys (ALT, CTRL, SHIFT, etc.) with other key presses to activate PyroSim actions.

The dialog is divided into three sections.

Global

These actions are available in most cases and generally match the behavior of other modeling tools.

View

Changes the way the current model is displayed.

Tool

Generally used to draw or to manually manipulate the model.

To change the keybinding for an action, click the value in the Key Press column. This launches an editor window (Figure 15) with four options.

Awaiting Input

Press a key to assign the desired keybinding and map it to the action.

Cancel

Exit the editor window without making any changes.

Reset

Assign the action it’s default keybinding.

Clear

Remove the currently assigned keybinding from the action.

Some keyboard shortcuts are used by Java UI components. If a shortcut does not result in the expected behavior, it may be in direct conflict with a preexisting Java shortcut. It is best practice to avoid these conflicts (Default Swing key bindings).

2.8.3. Record View Preferences

These preferences control the visualization of the FDS input file in the Record View. They can be seen in Figure 16.

Font Size

Change the size of the text used to display the FDS input file.

Enable Syntax Highlighting

Controls whether or not PyroSim uses colors to improve readability of the FDS input file. Disabling this option will cause the record view to update faster and consume less memory.

Set Limit for Highlighting HOLE and OBST records

Sets the total number of HOLE and OBST records to highlight in the FDS input file, which improves readability. Increasing this value will decrease performance and consume more memory, and decreasing this value will increase performance and consume less memory.

2.8.4. FDS Preferences

These preferences define the execution of FDS within PyroSim. They can be seen in Figure 17.

Executable Locations

Allow you to specify the FDS and Smokeview executables that are used by PyroSim.

Optimize Processor Utilization

Controls how meshes are distributed between available MPI processes.

Basic (Default)

PyroSim distributes meshes evenly across MPI processes.

None

PyroSim allows MPI to manage mesh distribution (default prior to PyroSim 2020.3). MPI assigns one mesh to all available MPI processes, however if the model has more meshes than available logical processors the last MPI process will be assigned multiple meshes. This can lead to increased simulation time.

Auto-save PyroSim model before running FDS

Controls whether PyroSim automatically saves the current PyroSim file just before beginning an FDS simulation.

Run Results when FDS simulation completes

Indicates whether to automatically launch the PyroSim 3D Results when an FDS simulation completes.

Parallel Execution Settings

Controls the number of MPI processes that are generated when using Parallel execution.

Create Process for Each Mesh

Creates one MPI process for each FDS mesh.

Limit Processes Based on Logical Processor Count (Default)

Creates one MPI process for each logical processor available.

FDS GEOM

Controls parameters related to immersed boundary obstructions, which is a new type of obstruction coming in a future release of FDS. The current release of FDS provides preliminary support for these types of obstructions but does not yet provide a guarantee on their level of support. Unlike normal obstructions, immersed boundary obstructions do not need to be converted to blocks when writing to the FDS input file. Instead, FDS will use their surfaces to cut FDS cells for more accurate geometry representations.

Enable FDS GEOM

Enables support for immersed boundary obstructions in the PyroSim user interface. If checked, additional actions are provided to convert obstructions into immersed boundary obstructions as discussed in Section 8.1.5 and to write them to the FDS input file. When importing an FDS file with immersed obstruction (GEOM) records, this option must be checked in order for those objects to be written as GEOM records; otherwise, they will be rasterized like other obstructions.

Validate GEOM obstructions

Indicates whether the geometry of obstructions should be validated when converting to immersed obstructions. FDS' specification for immersed geometry is fairly strict in that an object’s faces must form a closed, manifold volume. The validation process attempts to correct slight errors in the geometry to ensure a closed manifold is generated. It may cause conversion to take slightly longer but will help reduce geometry errors when writing the FDS input file. It is recommended to leave this option enabled. See Section 8.1.5 for more information.

2.8.5. Results Preferences

There are a number of preferences that control the files created by PyroSim when an FDS simulation is started that affect the results (either PyroSim 3D Results or Smokeview).

Include mesh boundaries in CAD files

Whether to include the non-open boundaries of the meshes in any CAD files that are written.

Output Views file

Whether to output a file that ends with the .views extension. This file contains information for all the views in the model (see Chapter 3) and can only be read by the PyroSim 3D Results. Enabling the views file prevents views from being written to the Smokeview INI file, see Section 3.4.

Output PyroGeom file

Whether to output a file that contains all CAD, obstruction, and vent geometry that can be viewed in the PyroSim 3D Results. This file represents the geometry before being converted to blocks for FDS and provides a high-quality visual in the 3D results. Objects in this file are also properly animated (turned on/off) if the objects have control logic associated with them, unlike the GE1 file.

Output INI file

Whether to output an INI file for Smokeview. This file contains shading information and some initialization information. If Output View file is unchecked, it also includes view information for Smokeview.

Output GE1 file

Whether to output a GE1 file. The GE1 file is similar to the PyroGeom file in that it includes CAD, obstruction, and vent geometry before block conversion. While this file format is viewable in both PyroSim 3D Results and Smokeview, it has some limitations:

• CAD texture coordinates may not map properly.
• Objects with control logic are not animated.

Show GE1 file by default

Whether to show the GE1 file by default in Smokeview rather than snapped obstructions and vents. This option can only be used if Output INI file is also checked.

2.8.6. Rendering and Display Preferences

These preferences define advanced 2D and 3D display properties, as shown in Figure 19. They can be used to improve display performance on complex models, but they tend to create problems for some older graphics cards, including crashing. For this reason, they are turned off when running in safe mode.

GPU Information

Provides information about the graphics hardware being used to render the 3d and 2d graphics.

Hardware accelerated cursor

When checked, mouse crosshairs and object editing will remain smooth even on complex geometry that may be slow to pan or orbit. PyroSim does this by rendering the scene into an image buffer and then rendering that buffer as a texture underneath the crosshairs or editing geometry whenever the mouse cursor moves.

Hardware accelerated vertex buffers

When checked, this can significantly improve rendering performance of complex geometry. PyroSim does this by storing the geometry in vertex buffers on the graphics card. PyroSim then makes very few OpenGL calls to render the geometry.

Scene Geometry

Controls how scene geometry is rendered.

Use Hardware Shaders

Uses OpenGL shaders to render the scene geometry if available. Typically, the use of shaders will improve the shading quality of objects and on some GPUs may significantly increase performance.

Use Compatibility Renderer

Uses the fixed-function OpenGL pipeline to render geometry. This is compatible with older GPUs.

Multisamples

Controls the antialiasing setting to smooth edges of objects. The values available depend on the GPU, but typically range from 0 to 16. A value of 0 will turn antialiasing off and will cause edges of objects to look jagged. Larger values increase visual quality, but may lower performance, depending on the GPU. A value of 4 usually provides a reasonable balance between quality and speed.

Anisotropic Filtering

Controls the texture quality when textured geometry is viewed at a large angle to the camera. Available values depend on the GPU and typically range from 1 to 16, where 1 turns off anisotropic filtering. Larger values improve the texture quality. Most GPUs see negligible performance impact setting this to a high value.

2.9. Configuration Files

PyroSim stores data related to user preferences in a file called PyroSim.props. By default, this file can be found in one of the following locations.

%APPDATA%\PyroSim\PyroSim.props
%PROGRAMDATA%\PyroSim\PyroSim.props

If at least one of these files exists, PyroSim will use it to load the user preferences. If both files exist, PyroSim will load user preferences from both files, giving preference to the file located in the APPDATA folder. This way the preference file located in the PROGRAMDATA folder can be shared among multiple machines, and the file located in the APPDATA folder on each machine overrides the shared settings.

The PROPS file is stored in a plaintext format, and can be viewed or edited with any conventional text editor. While it is not recommended to edit the file directly, some troubleshooting techniques may involve deleting the PROPS file so that a new one can be created from scratch by PyroSim.

Configurations for hotkeys in PyroSim is stored in a separate file named keybindings.json located in the APPDATA folder.

2.10. Units

Models can be created in either English or Metric units. To select a system of units, on the View menu, click Units, then click the desired unit. PyroSim will automatically convert your previous input values into the unit system you select. The Record View will always display values in the appropriate FDS units, regardless of what unit system you choose to work in.

2.11. Color Schemes

To select a Default, Black Background, White Background, or Custom color scheme, on the View menu, click Color Scheme. The custom color scheme is defined in the PyroSim.props file in the PyroSim installation directory (For Windows 10 look in %USERPROFILE%\AppData\Roaming\PyroSim\PyroSim.props while some older operating systems use C:\Program Files\PyroSim).

Colors.Custom.axis=0xffff00
Colors.Custom.axis.box=0x404040
Colors.Custom.axis.text=0xffffff
Colors.Custom.background=0x0
Colors.Custom.boundary.line=0xffffff
Colors.Custom.grid=0x4d4d66
Colors.Custom.group.highlight=0xffff00
Colors.Custom.heatDetector=0xff0000
Colors.Custom.obst=0xff0000
Colors.Custom.obst.highlight=0xb2b200
Colors.Custom.origin2D=0x737373
Colors.Custom.smokeDetector=0xff00
Colors.Custom.snap.point=0xff00
Colors.Custom.snapto.grid=0x404040
Colors.Custom.snapto.points=0xc0c0c0
Colors.Custom.sprk=0xff
Colors.Custom.text=0xffffff
Colors.Custom.thcp=0xffff00
Colors.Custom.tool=0xff00
Colors.Custom.tool.guides=0x7c00

3.1. Managing Views

Views are managed in the navigation view. From there, they can be created, deleted, grouped, rearranged, etc.

A view can be created in one of the following ways:

This will add a new view to the model, saving the current camera viewpoint and section box into the new view (see the following sections to learn more about viewpoints and section boxes). The new view will become the active view.

To delete a view, select it in the navigation view and in the Edit menu, select Delete. A view can only be deleted if it is not active.

To activate a view, perform one of the following:

Activating a view will restore all its saved state as described in the following sections.

View settings can be copied or moved between views. To copy settings such as the viewpoint or section box select Copy, located in either the navigation view or in the Edit menu. To paste the settings to another view, select the desired target view and in the Edit menu select Paste. To move settings from one view to another, in the navigation view, drag the setting to the desired view.

3.2. Viewpoints

Each view can have one viewpoint associated with it. A viewpoint includes the 2D or 3D camera’s position, orientation, zoom, and camera type (3D versus 2D). When a viewpoint is saved, the current navigation tool is also saved with the view (Orbit, Roam, etc.). A viewpoint appears in the navigation view as a child item of a view and is labelled Viewpoint. This can be seen in Figure 20 for the two views, Inside and Section.

A viewpoint is automatically saved to newly created views. A viewpoint can also be explicitly saved in one of the following ways:

The scene camera can be reset to a viewpoint in one of the following ways:

A viewpoint can be removed from a view by selecting the item, Viewpoint, in the navigation view and deleting it.

When a view with a viewpoint is activated, the following occurs:

3.3. Section Boxes

A section box may also be added to a view. A section box is a convex region defined by six sides that is used to limit the scope of visible geometry. All geometry outside the box is clipped from view. An example of the clipping is shown below.

Effect of a Section Box

A section box can be created in several ways:

A section box is displayed as a dashed outline of the region. Each section box has a color associated with it that is used to display both the outline of the section box and the clipped portions of solid, clipped objects as shown in Effect of a Section Box, Figure 21. In this figure, the section box is green, so any geometry that is clipped including the walls and slab in the image are also colored green.

The scope of a section box can be edited by selecting the section box and manipulating it like any other geometric object, see Section 9.16. Section boxes can also be rotated and moved like other geometric items, see Section 9.17.

The properties of a section box can be edited by either double-clicking the section box or by right-clicking it and selecting Properties.

See Figure 23 below.

The active section box can be disabled in the 2D or 3D view by de-selecting Enable Section Boxes in the View menu. The display for the section box can be independently hidden from view by de-selecting Show Section Boxes in the View menu.

A section box can also be reset to encompass the currently visible objects by performing one of the following:

3.4. Smokeview Interoperability

Smokeview supports the concept of viewpoints, which are similar to PyroSim views. Smokeview viewpoints are defined by camera position, orientation, a navigation tool, and up to six axis-aligned clipping planes. Viewpoints are stored in the Smokeview INI file.

By default, when PyroSim prepares an FDS simulation or exports an FDS file, it also writes a Views file that can be read in the PyroSim 3D Results but not Smokeview. It does not write the views to the Smokeview INI file. This is to avoid view duplication in the 3D Results. This behavior can be changed, however, by turning off the Views file in the preferences, see Section 2.8. If turned off, PyroSim will instead write the view information to the INI file, which can be read in Smokeview.

At any time, the view information can be updated for the results without re-running the simulation by explicitly writing either the PyroSim Views file or the Smokeview INI file. This can be done by going to the File menu, and selecting either Export→PyroSim Viewpoints or Export→Smokeview INI, respectively.

While the Views file exports views exactly as defined in PyroSim, there are some limitations to how PyroSim views are exported to the Smokeview INI file:

In addition, if a view was saved in PyroSim with the Roam tool active, the Rotation type in Smokeview is set to Eye centered. For all other navigation tools, the Rotation type in Smokeview is set to 2 axis.

Smokeview viewpoints may also be imported into PyroSim. This is useful if additional views have been specified in Smokeview while viewing the results and those viewpoints should be preserved in PyroSim. To import Smokeview viewpoints, perform the following:

After importing, a new view group is added, containing one PyroSim view for each Smokeview viewpoint that was in the INI file.

4.1. Creating a New PyroSim Model

When PyroSim is started, it begins with an empty model. You can close the current model and create a new empty model by opening the File menu and clicking New. PyroSim always has one (and only one) active model.

4.2. Saving a PyroSim Model

The PyroSim model file (PSM) is stored in a binary format that represents a PyroSim model. The PyroSim model contains all the information needed to write an FDS input file, as well as additional information such as obstruction grouping, floor heights, background images, and textures. This format is ideal for sharing your models with other PyroSim users.

To save a new model:

4.3. Open a Saved PyroSim Model

PyroSim model files have a PSM extension. To open a saved model:

A list of recently opened files is also available. To open recent files, on the File menu, click Recent PyroSim Files, then click the desired file.

PyroSim has an auto-save feature which stores a copy of your current model every 10 minutes. This file is automatically deleted if PyroSim exits normally, but if PyroSim crashes, you can recover your work by opening the autosave file. It can be found either in the same directory as your most recent PSM file, or in the PyroSim installation directory if your model was unsaved.

For more information about opening files saved with previous versions of PyroSim, please refer to Appendix A and Appendix B.

4.4. Preventing Changes to a Model

PyroSim supports write protection for a model. When write protection is enabled, users cannot modify a model (e.g. change geometry, edit surface properties, etc). This option can be enabled with or without password protection. If a model is write-protected, PyroSim will display notification in the application title bar.

To add write protection to a model:

The model will now be write-protected. Since a password was not used, a password will not be required to remove write protection.

To remove write protection from a model:

The model can now be edited. If needed, the dialog will require a password to release the lock.

4.5. Importing FDS Models

PyroSim allows you to import existing FDS input files. When you import an FDS file, PyroSim will create a new PyroSim model from the imported file. During import, PyroSim will check for the validity of each record. If errors are detected, you will be notified. You may then make the required corrections and attempt to import the file again.

To import existing FDS models into PyroSim:

PyroSim supports file import for versions 4, 5, and 6 of FDS. For more information about opening files compatible with version 4 or 5 of FDS, please refer to Appendix A and Appendix B.

4.6. Exporting FDS Models

PyroSim also allows you to explicitly export the current model to an FDS input file. You can manually edit the file to take advantage of advanced FDS features, or to easily transfer the input file to a different machine or special version of FDS.

To export an FDS file:

The file exported by PyroSim will be compatible with version 6 of FDS.

4.7. Importing CAD files

PyroSim can import geometry from several CAD formats, including buildingSMART’s IFC format for Building Information Models (BIM), AutoCAD’s DXF (Drawing Exchange Format), DWG, FBX, DAE, OBJ, GLTF/GLB 2.0, and STL files. Each type of file provides a variety of geometry that can either be directly represented as obstructions or as drawing guides in the PyroSim model.

Unlike FDS import, which completely replaces the current PyroSim model, CAD import appends the data to the current model. This facilitates the ability to import data from several CAD files into one PyroSim model. This is useful when there is one blueprint per floor of a building or a 3D building has been split into several sections, each in a separate file.

To import one of these files, under the File menu, select Import FDS/CAD File and select the desired file.

STL files will import as shown in Section 4.7.1. For non-STL files, a step-by-step dialog will open as shown in Figure 24.

When PyroSim imports a CAD file, it will treat all 3D face data as obstructions and all other data (lines, curves, etc.) as separate CAD data. If an object in the file contains both face and CAD data, the entity will be split into two entities so that CAD data can be easily deleted or hidden after import using the CAD filter button on the 3D/2D View toolbar, see Section 2.3.6.

An object with CAD data can be snapped to while drawing in PyroSim but is not converted to any type of FDS geometry.

In DWG and DXF files, an entity with face data will either be treated as a single, solid obstruction with some volume or as a collection of thin obstructions depending on the entity type in the DWG/DXF file. These objects will be represented as FDS geometry. The following DWG/DXF entity types are treated as solids in PyroSim:

With the exception of IFC files, all other entities and objects from other CAD formats that contain faces are treated as collections of thin obstructions by PyroSim. They cannot be reliably treated as solid since there is no guarantee that their faces form a closed and non-self-intersecting shell or that this would even be desired.

Once the file is imported, PyroSim creates a hierarchy of groups and objects, such that there is one top group, named after the file. The next levels depend on the imported file type. For non-DWG/DXF files, the structure will mimic the node structure in the source file. For DWG/FXF files, the next level contains a group for every layer containing geometry. Under each layer group there are one or more objects representing the entities in the file. The following illustrates the hierarchy as it would appear in the Navigation View:

If the DWG/DXF file contains a block insert and the block contains entities from multiple layers, the block insert is split into several PyroSim objects, one for each layer of the block’s originating entities. If all the entities in the block are from the same layer, however, there will be one resulting PyroSim object that will belong to the group corresponding to the block’s entities' layer rather than the block insert’s layer.

4.7.1. Importing STL Files

PyroSim can also import objects from STL files, which are simply listings of triangles. Usually, each STL file represents the shell of one 3D solid object.

To import an STL file, perform the following:

1. On the File menu, select Import FDS/CAD File. or click the Import button () on the main toolbar.
2. Select the desired STL file and click Open.
3. Enter the import options in the STL Import Options dialog as shown in Figure 27.
4. Click OK to begin import.

In Figure 27, the following options can be specified:

File Units

The units used to store the 3D coordinates in the STL file.

Vertex weld tolerance

A distance used to determine how far apart vertices must be to be considered separate.

Resulting Geometry Type

Filled Obstruction

Imports the triangles as solid obstructions. The triangles must form one or more closed, manifold collections of triangles. Each collection of connected triangles is treated as a separate shell. The shells are grouped such that if one shell is immediately inside another shell, the outside shell defines the outside of the solid, and the interior shell defines a hole/cavity in the solid. This option should not be used if there are several touching or intersecting solids. If this is the case, it is preferable to import the objects using a different file type.

Hollow Obstruction

Imports the triangles as is. Each set of connected triangles is treated as a separate unfilled obstruction.

Unstructured GEOM

Imports the triangles as immersed boundary obstructions. The geometry must follow the same rules as with the Filled Obstruction option. See FDS GEOM for more information about immersed boundary obstructions.

Hole

Imports the triangles as holes that will be subtracted from existing obstructions. The geometry must follow the same rules as with the Filled Obstruction option.

Surface

The surface to apply to the resulting obstructions if applicable.

Convert to solid obstructions

Whether to treat the resulting objects as solid obstructions. If this is unchecked, each resulting object will be a collection of thin obstructions.

Because the STL file is simply a listing of triangles, there may be more than one object represented in the file. PyroSim will use the vertex weld tolerance to detect triangle connectivity and determine if there are several, disconnected sets of faces in the file. If there are, there will be one resulting PyroSim object per connected set of faces.

In addition, if the solid option is enabled or the objects are being treated as holes, import will only succeed if each face set is detected as a closed shell by PyroSim.

5.1. Working with Meshes

All FDS calculations are performed within computational meshes. Every object in the simulation (e.g. obstructions and vents) must conform to the mesh. When an object’s location doesn’t exactly conform to a mesh, the object is automatically repositioned during the simulation. Any object that extends beyond the boundary of the physical domain is cut off at the boundary. There is no penalty for defining objects outside of the domain, but these objects do not appear in the Results.

To achieve optimal simulation accuracy, it is important to use mesh cells that are approximately the same size in all three directions.

FDS uses a Poisson solver based on Fast Fourier Transforms (FFTs). A side effect of this approach is that optimal mesh divisions are constrained to the form 2^u 3^v 5^w, where u, v and w are integers. For example, 64 = 2⁶, 72 = 2³ * 3², and 108 = 2² * 3³ are good mesh dimensions. However, 37, 99 and 109 are not. In addition, using a prime number of cells along an axis may cause undesirable results. PyroSim warns when the number of divisions is not optimal.

5.2. Uniform Meshes

This example illustrates creating a multiple mesh model.

To create the first mesh:

The 3D View will now display the resulting mesh.

5.3. Nonuniform Meshes

To create a second, nonuniform mesh:

You can click or type Ctrl+R to reset the model. The resulting meshes are displayed below.

5.4. Using Multiple Meshes

The term "multiple meshes" means that the computational domain consists of more than one rectangular mesh, usually connected, although this is not required. In each mesh, the governing equations can be solved with a time step based on the flow speed within that particular mesh. Some reasons for using multiple meshes include:

Meshes can overlap, abut, or not touch at all. In the last case, essentially two separate calculations are performed with no communication at all between them. Obstructions and vents are entered in terms of the overall coordinate system and need not apply to any one particular mesh. Each mesh checks the coordinates of all the geometric entities and decides whether or not they are to be included.

As described in the FDS User Guide (McGrattan et al. 2021) the following rules of thumb should also be followed when setting up a multiple mesh calculation:

Correct Mesh Alignment Examples

Incorrect Mesh Alignment Examples

5.5. Additional Mesh Actions

To simplify working with multiple meshes, PyroSim provides the following additional mesh operations:

To use any of the above actions, select one or more meshes, right-click to open a popup menu, then click the desired mesh action.

6.1. Solid Materials

Examples of solid materials include brick, gypsum board, and upholstery. To create a solid material:

After following these steps, a default solid material will be created. Text entered in the Description box will not affect the simulation, but will be preserved in the FDS input file using the FYI field of the material. Including a description of the material is recommended.

The Thermal Properties tab provides the following options:

The Pyrolysis tab provides options to set the heat of combustion and add reactions that will be used to govern how the material burns.

Each material can have a maximum of 10 reactions. To add a reaction, click the Add button. This will open a dialog to edit the new reaction. It provides the following options:

On the Rate tab:

On the Byproducts tab:

6.2. Liquid Fuels

Examples of liquid fuels include kerosene and ethanol.

To create a liquid fuel:

After following these steps, a default solid material will be created. Text entered in the Description box will not affect the simulation, but will be preserved in the FDS input file using the FYI field of the material. Including a description of the material is recommended.

The thermal properties tab for liquid fuels is identical to the thermal properties tab for solid fuels, see Section 6.1.

The Pyrolysis tab provides the following parameters:

7.1. Reserved Surfaces

There are six fundamental or "reserved" surface types: ADIABATIC, INERT, MIRROR, OPEN, HVAC, and PERIODIC. These surfaces cannot be changed and are present in every analysis.

7.2. Surface Types

PyroSim aids the user by organizing the surface options into logical types, such as a burner to define a simple fire or a layered surface to represent a solid, heat conducting wall.

There are eight surface types in alphabetical order that you can create in PyroSim.

The Edit Surfaces dialog helps define a surface type with a set of tabs. Each tab provides a collection of input fields and settings for the user to customize that surface type.

7.3. Surface Tabs

Each tab of the Edit Surfaces dialog provides a set of inputs and settings that can be used to build a custom surface type as listed in Section 7.2. The following sections describe the parameters on each tab and are listed in alphabetical order, not the order they might appear for a surface type.

7.3.3. Air Flow

Specify Volume Flow

Use a constant volume flux to define air movement through the vent.

Specify Velocity

Use a constant velocity to define air movement through the vent.

Specify Total Mass Flux

Use a constant mass flux to define air movement through the vent.

Specify Mass Flux of Individual Species

Define air movement through the vent using a table of species and their mass fluxes. This method requires a model that includes extra (non-reactive) species. Flux data is specified on the Species Injection tab.

Tangential Velocity

The tangential velocity of the air flow. The first parameter is the velocity in the X or Y direction and the second parameter is in the Y or Z direction, depending on the normal direction of the vent. An example is shown in Figure 36.

Ramp-Up Time

At the beginning of the simulation, vents with this surface will not be blowing. This parameter controls the time it takes to ramp the air flow up to the specified amount.

Wind Profile

The default wind profile is constant (Top Hat), to model wind conditions outdoors there are two additional options: parabolic and atmospheric.

Parabolic

Produces wind with a parabolic profile whose maximum is the specified velocity.

Atmospheric

Produces a wind profile of the form \(u=u_0(z/z_0)^p\).

Atmospheric Profile Exponent

The term \(p\) in the atmospheric profile equation. This option is only available when atmospheric profile is selected.

Atmospheric Profile Origin

The term \(z_0\) in the atmospheric profile equation. This option is only available when atmospheric profile is selected.

7.4. Surface Color and Appearance

Each surface has an associated Color value that defines the color and opacity (also known as Alpha) of the obstructions using that surface. Each referencing obstruction may optionally override the color/opacity value in the Obstructions Dialog.

A surface may also define an optional Appearance that specifies more advanced attributes, such as textures or lighting details to increase the realism of the model. When an Appearance is defined for a surface, the Appearance may override both the surface’s and the object’s color/opacity settings when the View Mode is set to Realistic or Realistic with Outlines. The exception is when the Appearance’s Diffuse/Albedo option is set to From Object Color. See Appearance Properties for more information.

Some default appearances are provided with PyroSim or you can import your own. The Room Fire example demonstrates using a wood texture for a pine floor and hanging a picture on a wall. Your textures will be automatically displayed in PyroSim.

To define an appearance with a texture and attach it to a Surface:

Appearances can also be viewed by going to the Model menu and selecting Edit Appearances. This will show the Appearances Dialog.

Appearances can be added manually by clicking New under the appearance list. Newly created appearances are added to the database, and can be used across instances of PyroSim.

Appearances can be deleted by clicking Remove under the appearance list. If the appearance exists in the database, all its associated files in the database directory will also be permanently removed.

The following appearance properties can be edited from this dialog:

7.4.1. Advanced Appearance Properties

Additional appearance properties can be edited by pressing the Advanced Materials button. This will show the Advanced Materials Dialog for the currently selected material.

Most properties in this dialog can be specified as either a constant color/value or as a texture image. For those properties that represent a single value as opposed to a color, such as the Roughness value for PBR workflow, a dropdown next to the texture chooser can be used to pick which color component is the source of the values. This is useful when multiple properties are packed into a single image, but in different color components. For instance, say the PBR parameters, metallic, roughness, and ambient occlusion, are packed into the red, green, and blue color components of a single image. In this case, the same image can be chosen for the metallic, roughness, and ambient occlusion textures. The dropdowns next to each texture would be set to R, G, and B, respectively.

The following appearance properties can be edited from this dialog:

Ambient

Defines the color used to modulate ambient lighting applied to the appearance. This will only be applied when Image Based Lighting is disabled. Selecting the From Diffuse/Albedo option for this channel causes the Diffuse channel value to modulate ambient lighting instead.

Emissive

Defines the amount and color of light emitted by the appearance.

Normal/Bump

Whether to use normal mapping or bump mapping for the appearance.

Normal

The normal map used for the appearance.

Y-Down Normals

Whether or not to invert the y-component of the provided normals. This should be enabled for normal maps designed for DirectX. Check any documentation that comes with the appearance to determine if this applies.

Bump

The bump map used for the appearance.

Bump Scale

The strength of the bump map effect.

Displacement/Height

The parallax displacement or height map to use.

Parallax Scale

The strength of the parallax mapping effect. This unit of this scale is purely visual, but it should be kept low to prevent rendering artifacts.

Invert Parallax

Whether or not to invert the displacement/height map. This should be enabled for height maps.

Workflow

The appearance workflow to use. Provided options are Specular (Basic), Metallic (PBR), and Specular (PBR). Appearances with a Specular map are designed for either the Specular (Basic) or Specular (PBR) workflow. Specular appearances with a Roughness, Glossiness, or Ambient Occlusion map are meant for the Specular (PBR) workflow. Appearances with a Metallic map are designed for the Metallic (PBR) workflow.

Depending on which workflow is selected, the following additional properties are provided:

Specular

Defines the specular reflectance of the appearance. This property is only available in the Specular (Basic) and Specular (PBR) workflows.

Metallic

Defines whether or not the appearance is metallic. This property is only available in the Metallic (PBR) workflow.

Shininess

Defines how shiny the appearance’s surface is. This property is only available in the Specular (Basic) workflow.

Roughness/Glossiness

Determines whether to use roughness or glossiness to define the appearance’s microsurface. This option is only available in the Metallic (PBR) and Specular (PBR) workflows.

Roughness

Defines how rough an appearance’s microsurface is. This is the exact inverse of Glossiness. This option is only available in the Metallic (PBR) and Specular (PBR) workflows.

Glossiness

Defines how glossy an appearance’s microsurface is. This is the exact inverse of Roughness. This option is only available in the Metallic (PBR) and Specular (PBR) workflows.

Ambient Occlusion

Provides additional shading information for the appearance. Note that this property is not related to the scene-wide Ambient Occlusion in Results. This property is only available in the Metallic (PBR) and Specular (PBR) workflows.

Invert Ambient Occlusion

Whether to invert the values read from the ambient occlusion texture (ao_inverted = 1.0 - ao_texture). This is useful when the ambient occlusion texture specifies the amount of occlusion (increasing values lead to more occlusion) rather than amount of visible light (lower values lead to more occlusion).

8.1. Obstructions

Obstructions are the fundamental geometric representation in FDS. In FDS, obstructions are rectangular, axis-aligned solids defined by two points. Surface properties are assigned to each face of the obstruction. In PyroSim, obstructions can take any shape, have any number of faces, and have different surfaces applied to each face. At the time of simulation, PyroSim will automatically convert the obstructions to axis-aligned blocks required by FDS as discussed in Section 19.1.8.

FDS defines three types of obstructions:

Conversion of a slab obstruction to FDS blocks shows an example of a polygonal slab drawn in PyroSim (Figure 39) and its conversion to blocks for use in FDS (Figure 40).

Conversion of a slab obstruction to FDS blocks

8.1.1. Creating Obstructions

To create a new obstruction, either use an obstruction drawing tool as discussed in Chapter 9 or on the Model menu, click New Obstruction. or New Slab.

8.1.5. Converting to an Immersed Obstruction

If FDS GEOM is enabled, obstructions must be manually converted into immersed boundary obstructions in order for them to be written as GEOM records in the FDS input file. This can be accomplished in two ways:

• Double-click the obstruction to edit its properties, check the box next to Write as Geom, and press OK. The object can be converted back by unchecking Write as Geom.
• Right-click the desired obstructions to convert and select Write as GEOM. The objects can be converted back to regular obstructions by selecting Write as OBST instead.

In either case, if Validate GEOM obstructions is enabled in the preferences dialog (see FDS GEOM), a dialog will appear as shown in Figure 42. This dialog can be used to specify how the selected objects should be validated such that they can be converted to immersed obstructions. FDS requires that an immersed obstruction consists of a closed, manifold set of faces defining a volume. This requires that each face connect to exactly one other face on each edge and that the object does not self-intersect. Imported CAD objects often do not meet this criteria, so PyroSim’s validation process can help check and in many cases fix issues that arise.

The following validation options are available in the Convert to GEOM dialog:

Conversion Mode

Controls how geometry will be checked and whether to attempt to fix the geometry. The following modes are available:

Quick

Performs a basic test to see if the object appears manifold, but does not check for self-intersection or attempt to clean the object. This option is the fastest and ensures the object’s geometry will not change, but it also cannot fix errors in the object’s geometry.

Clean if non-manifold

Checks if the object appears to be manifold, and if not, performs an object cleanup. This option will only change the object’s geometry if necessary, but it might not correct the geometry of objects that self-intersect.

Force cleanup

Forces the object to be cleaned if possible. This option will likely change the geometry of the object, but it will ensure the object does not self-intersect.

Geometry Clean-up

Specifies additional geometry clean-up options to help ensure an object is manifold:

Remove internal faces

Removes invalid faces that appear to be internal to the object. In certain cases, this option may remove valid portions of the object. Uncheck if this happens.

Remove vestigial non-manifold faces

Removes faces that are not connected to others on at least one edge in an attempt to make the object manifold.

When PyroSim cleans geometry for an immersed obstruction, it will always attempt to apply the following set of fixes:

• Vertices that are very close within a tolerance are merged together.
• Vertices that lie on or very near another edge will split the edge.
• Edges that intersect (or nearly intersect) will be split at the intersection point.
• Edges that intersect faces will be split at the intersection point.
• Faces that intersect each other will be split along the intersection line.

8.2. Holes

Holes are used to carve negative spaces out of obstructions. In FDS, holes are similar to obstructions in that they are defined as axis-aligned blocks. Like obstructions in PyroSim, however, holes can be any shape. PyroSim automatically converts them to blocks in the FDS input file.

PyroSim treats holes as first-class objects that can be selected, deleted, and have other operations performed on them like obstructions as discussed in Chapter 11.

In the 3D and 2D views, holes appear as transparent objects. In addition, for display purposes only, PyroSim carves holes out of obstructions as shown in Figure 43. For complex holes or obstructions or large holes that span many obstructions, this process may be slow. In these cases, hole-cutting display can be turned off by going to the View menu and deselecting Cut Holes From Obstructions.

By default, all obstructions allow holes to be cut from them. To prevent an obstruction from allowing holes, edit the properties of the obstruction as discussed in Section 8.1 and deselect Permit Holes.

There are various rules that govern how holes are written to the FDS input file. In general, if the PYROGEOM file is enabled, a hole has control logic, and the hole intersects obstructions, the hole will be pre-subtracted from obstructions before the obstructions are converted into blocks, and the holes will be excluded from the FDS file. If the above conditions do not hold, the holes are converted to blocks similarly to obstructions and are written as HOLE records. For more information, see Section 19.8.

8.2.1. Creating Holes

Holes can either be drawn as discussed in Chapter 9 or can be created by opening the Model menu and clicking New Hole.

This will open the Hole Properties dialog as shown in Figure 44.

Like obstructions, holes can also be activated as discussed in Chapter 16. Holes can also have a color applied.

8.2.2. Holes at Mesh Boundaries

When starting a simulation or exporting an FDS file for some models, the user may receive the following message as shown in Figure 45: "PyroSim has detected a hole touching a mesh boundary, which may cause cutting problems in FDS. Would you like to slightly expand these types of holes?"

FDS currently has an issue where it will not fully cut a hole from an obstruction if both the hole and obstruction touch a mesh boundary at the same location. Instead, FDS leaves a thin obstruction along the mesh boundary. Figure 46 shows a model in PyroSim that can lead this problem. In this model, both the hole and the obstruction touch the bottom of the mesh, and the hole should cut all the way through the mesh. Figure 47 shows this model in FDS where the hole has not been punched all the way through the obstruction.

PyroSim detects potential cases where this might happen and prompts the user with the Expand Boundary Holes dialog. If the user chooses to expand the hole (the Yes option), PyroSim will expand the hole to 1/10 of a mesh cell past the mesh boundary for every side of the hole that touches a mesh boundary. This ensures the hole is properly cut all the way through the obstruction as shown in Figure 48. If the user chooses not to expand these types of holes (the No option), the hole will be written exactly as specified and may lead to the thin obstruction problem.

Cutting holes in mesh boundaries

8.3. Vents

Vents have general usage in FDS to describe a 2D rectangular patch on the surface of a solid obstruction or on a mesh boundary as shown in Figure 49. A vent may have a different surface applied to it than the rest of the obstruction to which it is attached.

Taken literally, a vent can be used to model components of the ventilation system in a building, like a diffuser or a return. In these cases, the vent coordinates form a plane on a solid surface forming the boundary of the duct. No holes need to be created through the solid; it is assumed that air is pushed out of or sucked into duct work within the wall.

You can also use vents as a means of applying a particular boundary condition to a rectangular patch on a solid surface. A fire, for example, is usually created by first generating a solid obstruction and then specifying a vent somewhere on one of the faces of the solid with the characteristics of the thermal and combustion properties of the fuel.

There are two reserved surface types that may be applied to a vent: OPEN and MIRROR. For more information on these types, see Chapter 7.

8.3.1. Creating Vents

Vents can either be drawn as discussed in Chapter 9 or be created by opening the Model menu and clicking New Vent.

This will open the New Vent dialog as shown in Figure 50. Like obstructions and holes, vents can also be activated, but only if the surface is not MIRROR or OPEN. With the exception of Fire Spread, the other properties are similar to obstructions. Fire Spread can be specified on vents using a burner surface (Chapter 7). This option simulates a radially spreading fire at the vent. A vent can also be given radial properties. Defining a Center Point and Radius for a vent will cause FDS to define a vent bounded by the vent’s Bounding Box and the circle generated by the point radius combination.

8.4. Groups

Groups can be used to hierarchically organize the model. Groups can only be seen in the Navigation View. The "Model" is the base group. Users can nest groups inside other groups, allowing the user to work with thousands of objects in an organized way. When the user performs an action on a group, that action will be propagated to all objects in the group.

8.4.1. Creating Groups

There are two ways to create a group:

• Right-click the desired parent group from the Navigation View and select New Group. from the context menu. This will create a child group in the selected parent.
• Click the New Group. button () from the main tool bar.

Both of these actions will show the Create Group dialog as shown in Figure 51. This dialog allows the user to choose the parent group and name of the new group.

8.4.2. Adding Objects to Groups

There are several ways to add objects to a group:

• For existing objects, in the Navigation View, select the objects and drag them into the desired group as shown in Dragging objects to a new group in the Navigation View.. Alternatively, right click them in any view and select Change Group.

In the Change Group dialog shown in Figure 55, select the desired group. If a new group is desired, select New Subgroup and specify a name. If this is chosen, a new group will be created under the specified existing group, and the selected objects will be moved to this new group. * For newly drawn objects, in the 3D or 2D view select the desired group from the group drop-down above the view as shown in Figure 56. All newly drawn objects will be added to this group.

Dragging objects to a new group in the Navigation View.

8.5. Floors

Floors are used in PyroSim to quickly apply clipping filters to the scene to only show a portion of the model. They are also used to initialize the properties of drawing tools so that they draw at the proper Z location.

An example of floor clipping is shown in Floor clipping, where Figure 57 shows all floors and Figure 58 shows a single floor.

Floor clipping

To define the floors in a model, go to the Navigation View and click the Define Floor Locations button (). This will display the Manage Floors dialog shown in Figure 59.

Floors are defined by the following properties:

To add a new floor, click on the Floor Drop-down above the Navigation View as shown in Figure 6 and select <Add New…​>. This will show the New Floor dialog as shown in Figure 60. By default this dialog will assume the user wants a floor above the previous floor using that floor’s slab thickness and wall height properties. In this dialog, if the user enters a new slab thickness, the elevation will be automatically updated so the new floor does not overlap the others unless the user enters a specific value for the elevation. In addition, unless the user enters a specific name, a name will be automatically generated based on the elevation.

Press OK to create the new floor.

Press OK again in the Manage Floors dialog to commit the changes.

By default, the model contains one floor at elevation 0.0 m with a slab thickness of .25 m and a wall height of 2.75 m. Using these values leaves a distance of 3.0 m from one floor elevation to another.

Once the floors have been defined, the user can filter the display to show either a single floor or all floors as shown in Figure 6. For most views, the Z clipping range for a particular floor is from the floor elevation minus slab thickness to floor elevation plus wall height. The Z clipping range works differently for the top camera of the 2D view, however. In this view, the clipping is from the elevation of the floor BELOW to the elevation plus wall height of the current floor. This allows the geometry on the floor below to be snapped to in drawing geometry for the current floor. For this to be useful, however, the user may want to use wireframe rendering.

8.5.2. Adding a Background Image to a Floor

Each floor can have an associated background image. To add a background image to a floor, go to the Navigation View, select a specific floor, then click the Configure Background Image button (). Alternately click the Define Floor Locations button, (), and then in the Background Image column, select the Edit button. This will display the Configure Background Image dialog shown in Figure 61.

You will be guided through the following steps:

1. Choose a background image file. Valid image formats are bmp, dxf, gif, jpg, png, tga, and tif.
2. Specify the Anchor Point for the image by clicking on the image. The Anchor Point is a point on the image at which the coordinates are specified in the model coordinate system. The model coordinates of the anchor point are not required to be at the origin.
3. Set the model scale. Select the Choose Point A button, then select the first point that will be used to define a length. Select the Choose Point B button and select the second point to define a length. Input the Distance between points A and B.
4. Use the sliding scale to change the image transparency.
5. If the image needs to be rotated, check the box next to Dist. A to B and enter an angle. This specifies the angle between the positive X axis and the vector from reference point A to B. For instance, if A→B should be aligned with the X axis, enter 0 for the angle or if A→B should be aligned with the positive Y axis, enter 90.
6. Click OK to close the Configure Background Image dialog.

Now, in the 3D or 2D views, when the user displays a specific floor, the background image for that floor will be displayed. To turn off the background images, go to the 2D or 3D View, and click the Show Background Images button () next to the floors drop-down.

9.1. Drawing/Editing Tool Overview

PyroSim provides several drawing and editing tools. These tools are located on the drawing toolbar at the left side of the 3D and 2D Views as shown in Figure 62.

Some of these tools allow a user to create and edit objects such as slabs and walls that are not constrained to the FDS mesh. In these cases, PyroSim will automatically convert the shapes to mesh-based blocks when the FDS input file is created. These blocks can be previewed by clicking the Preview FDS Blocks button () on the filter toolbar above the 3D or 2D View. For information on block conversion, see Section 19.1.8.

9.1.4. Quick Actions

In addition to the tool properties, each tool also has additional quick actions. To show these actions, start the desired tool and then right-click in the 2D or 3D View. This opens a context menu with the quick actions. Figure 63 shows an example of the quick action menu for the wall tool.

This menu allows the user to perform actions specific to the tool, such as closing a polygon, picking a surface, setting wall alignment, accessing the tool properties, etc.

9.2. Snapping

Snapping is one way to precisely draw and edit objects. It is the process of finding some element in the scene, such as a vertex or edge close to the cursor, and snapping the cursor to that element like a magnet.

In PyroSim, snapping can be performed against the solution meshes, objects in the model, and orthographic constraints. The 2D View additionally provides a sketch grid and polar (angle) constraints. If a snap point is found, an indicator dot shown in Figure 64 will appear at the snap point.

By default, snapping is enabled. It can be disabled by holding ALT on the keyboard while using a drawing/editing tool.

9.2.2. Sketch Grid Snapping (2D View Only)

PyroSim also provides a user-defined drawing grid, or sketch grid, in the 2D View as shown in Figure 65.

When a new model is created, the sketch grid is visible and can be snapped to in the 2D view. The default spacing for the divisions is 1 m, but can be changed by going to the View menu and clicking Set Sketch Grid Spacing.

Once the user has created a solution mesh, PyroSim will automatically switch to solution mesh snapping and disable sketch grid snapping. In the 2D View, PyroSim will only snap to the sketch grid or visible solution meshes. To switch which snapping is being used, on the View menu choose Snap to Sketch Grid or Snap to Model Grids. To disable grid snapping altogether, on the View menu choose Disable Grid Snapping.

9.2.4. Constraint Snapping

Constraints are dynamic snapping lines that are only visible when the cursor is near them. They appear as infinite dotted lines as shown in Figure 66.

PyroSim contains two types of constraints:

Orthographic

These constraints allow the user to snap to a line parallel to the X, Y, or Z axis from the last relevant point. For instance, when drawing a polygonal slab, after each point specified, there will be three orthographic constraints extending from the last drawn point to aid in drawing the next point.

Polar (2D View Only )

These constraints are similar to orthographic constraints, but they are found at 15 degree increments from the current view’s local X axis.

9.2.5. Constraint Locking

If a constraint is currently being snapped to, that constraint can be locked by holding SHIFT on the keyboard. While holding SHIFT, a second dotted line will extend from the cursor to the locked constraint (the first dotted line). This is useful for lining up objects along a constraint with other objects.

For instance, in Figure 67, a box already exists in the model. A second slab is being drawn such that the third point of the slab lines up with the right side of the first box. This was done as follows:

1. After the second point for the slab was clicked, the cursor was moved until the X-axis constraint became visible.
2. SHIFT was pressed and held on the keyboard to lock the constraint.
3. The cursor was moved to a point on the right edge of the box while still holding SHIFT.

9.3. Precise Keyboard Entry

While using a drawing/editing tool, a popup window may appear next to the cursor, such as in Figure 68. This window shows the value used to determine the next point or value for the current tool. In this figure the value is the Distance from the previous point along the vector from the previous point to the current cursor location. For other tools, this value may be angle or relative offset, etc.

The value is editable if the status bar at the bottom of the 3D or 2D View indicates it is. For instance, in the figure, the status bar says "<Type to enter Distance or press TAB for alternatives>". If the user starts typing, the popup window will be replaced with an editing window as shown in Figure 69. If the user presses ENTER, the typed value will be committed. If the user presses ESC instead, the keyboard entry will be cancelled.

Pressing TAB cycles through alternate input methods to determine the next value. For instance, pressing TAB with the wall tool allows the user to enter a relative offset from the last point instead of a distance. Pressing TAB a second time allows the user to enter an absolute position for the next point, and pressing TAB a third time will cycle back to the distance input.

Precise keyboard entry may be easiest for some users when using the multi-click mode of drawing rather than using the click-drag mode. Using multi-click allows both hands to be used to type as opposed to click-drag, which requires one hand to remain on the mouse.

9.4. 2D versus 3D Drawing

There are some key differences between drawing in the 2D and 3D Views. The 2D View is useful when drawing should be restricted to one pre-defined plane. It is also useful for lining up objects along the X, Y, or Z axes. The 3D View is useful when an object such as a vent or solid-phase device needs to be snapped to the face of an obstruction or vent or if the user would like to build objects by stacking them on top of one another.

9.4.1. 2D View Drawing

When drawing in the 2D View, the drawing will always take place in the drawing plane specified in the tool properties, and snapping is only performed in the local X and Y dimensions. The local Z value will remain true to the drawing plane. In addition, if a tool has some sort of height or depth property, the tool will also remain true to that value. Slabs in different planes aligned in the 2D View shows two slabs that have been drawn in the top view (Figure 70), one at Z = 0 m and the other at Z = 1.5 m. While snapping was used to partially align the objects, they both remain in the Z planes specified in their tool properties shown in the rotated view (Figure 71).

Slabs in different planes aligned in the 2D View

9.4.2. 3D View Drawing

The 3D View uses snapping in all three dimensions, causing tool properties to be interpreted more loosely. The drawing plane and depth properties for a drawn object are context-sensitive in the 3D View. When using tools such as the slab tool, the first clicked point determines the drawing plane. If, on this first click, another object is snapped to, the drawing plane is set at the Z location of that snap point. The tool properties' drawing plane is only used if nothing is snapped to on the first click.

This 3D snapping feature of the 3D View is useful for drawing vents on obstructions and attaching solid-phase devices to obstructions as shown in Figure 72.

The 3D snapping feature is also useful for stacking objects, as shown in Figure 73. In this figure, the drawing plane was never changed. All the objects were stacked on top of each other using snapping.

9.4.3. Holes in the 3D View

While stacking can be useful for obstructions, a user must be more careful when drawing holes in the 3D View. For instance, with the slab hole tool and block hole tool, the user will need to change the extrusion direction to properly direct the hole into the obstruction.

For instance, if the user draws a slab obstruction in the 3D View and then draws a slab hole while snapping to the obstruction, the hole will be stacked on top of the obstruction without cutting a hole as shown in Figure 74.

To draw this properly, the user would need to change the extrusion direction when drawing the hole by pressing CTRL on the keyboard or changing it through the tool’s right-click menu. This will result in a proper hole as shown in Figure 75.

This is not a problem in the 2D View since it always uses the drawing plane set in the tool properties instead of stacking the objects.

Improper vs proper hole drawing in the 3D view

9.4.4. Projected Drawing in the 3D View

Once the drawing plane for a tool has been established by the first click, the tool can still determine the next points by snapping to objects in another plane. In this case, the snapped points will be projected to the drawing plane for the current tool. A dotted line will show how the snapped point was projected to the plane. For instance, Figure 76 shows a new slab being drawn in the Z = 1.5 plane. A slab below the new slab is being snapped to determine the new slab’s points.

9.5. Obstruction Drawing Tools

There are four tools that can draw obstructions, for more information on obstructions, see Section 8.1.

Slab Obstruction Tool: Used to draw the slab for a floor.

Wall Obstruction Tool: Used to draw a wall.

Block Obstruction Tool: Used to fill grid cells with obstructions.

Room Tool: Used to draw a rectangular room

For all the obstruction tools, the tool properties dialog () will appear similar to that in Figure 77. The only section of the dialog that will change between these tools is the geometry, such as Z Location and Thickness. All other properties, including name, surface, color, and obstruction flags appear in all obstruction dialogs. These parameters control the properties that will be applied to the next drawn obstruction.

The surface and color of the next obstruction can also be set via the right-click menu for the tool.

9.5.1. Slab Obstruction Tool

A slab is an extruded polygonal object as shown in Figure 78 that can be used to draw the slab for a floor in a building.

The slab obstruction tool adds two additional properties to the tool dialog for obstructions:

[X,Y, or Z] Location

The drawing plane for the slab. When the active floor is changed, this is set to the floor’s elevation minus the floor’s slab thickness.

Thickness

The thickness of the slab. When the active floor is changed, this is set to the floor’s slab thickness. If this value is positive, the slab is extruded toward the camera. If it is negative the slab is extruded away from the camera. The extrusion direction can be toggled by pressing CTRL on the keyboard or from the tool’s right-click menu.

To draw the polygon vertices of the slab obstruction, perform the following:

1. Select the Slab Obstruction Tool () from the drawing toolbar.
2. Define the slab points using one of the two tool modes:
   • Use Click-drag mode to draw an axis-aligned box between two points.
   • Use Multi-click mode to click several points defining the polygonal boundary for the slab.

9.5.2. Wall Obstruction Tool

The wall obstruction tool () can be used to draw multi-segmented walls as shown in Figure 79. In this figure, there is only one wall. The user specifies a path along the floor from which the wall is extruded up. The wall can be aligned to the left, right, or center of the drawn path.

The wall obstruction tool adds three properties to the tool properties dialog:

Z Location

The drawing plane for the bottom of the wall. When the active floor is changed, this is set to the floor’s elevation property.

Height

The height of the wall as a positive number. When the active floor is changed, this is set to the floor’s wall height property.

Wall Thickness

The thickness of the wall.

The alignment of the wall can be controlled through the right-click menu for the tool or can be cycled by pressing the CTRL key on the keyboard. The alignment options are Left (Figure 80), Center (Figure 81) and Right (Figure 82) as shown in Wall alignment options.

Wall alignment options

To draw a wall, perform the following steps:

1. Select the Wall Obstruction Tool () from the drawing toolbar.
2. Define the wall points using one of the two tool modes:
   • Use Click-drag mode to draw a single wall segment.
   • Use Multi-click mode to click several points, with wall segments between each pair of points.

If the first clicked point is clicked again after drawing at least two segments or Close is chosen from the right-click menu, the tool will draw one last segment from the last clicked point to the first point and finish. Alternately, the wall can be ended at the last clicked point by choosing Finish from the right-click menu.

9.5.3. Block Obstruction Tool

The Block Obstruction Tool () can be used to quickly fill grid cells with blocks as shown in Figure 83 or place a block with a single click.

This tool adds the following properties to the tool properties dialog:

[X,Y, or Z] Location

The drawing plane. When the active floor is changed, this is set to the floor’s elevation.

Height

The distance the block is extruded toward or away from the camera. When the active floor is changed, this is set to the floor’s wall height property.

Size

The size of the block when there is no snap grid under the cursor.

In addition, the extrusion direction for the block can be toggled by pressing CTRL on the keyboard or through the right-click menu for the tool.

To create blocks using this tool, perform the following:

1. Select the Block Obstruction Tool () from the drawing toolbar.
2. If a solution mesh or sketch grid is visible, either click the desired cell to fill or click-drag the mouse across the grid to "paint" blocks. The depth of the cells will not necessarily be the depth of a cell in the filled mesh, however. The depth is strictly controlled by the height property for the tool.

9.5.4. Room Tool

The Room Tool () can be used to draw a rectangular room using one closed wall as shown in Figure 84.

The room tool contains the same properties as the wall obstruction tool.

To draw a room with the room tool perform the following:

1. Select the Room Tool () from the drawing toolbar.
2. Use Click-drag mode or Multi-click mode to draw two points defining the extents of the room.

9.6. Hole Drawing Tools

There are three tools that can draw holes, for more information on holes, see Section 8.2.

Slab Hole Tool: Used to draw a hole in a floor slab. Wall Hole Tool: Used to draw an opening in a wall, such as for a doorway or window. Block Hole Tool: Used to fill grid cells with holes.

All these tools work the same as their obstruction counterparts, but they do not have the properties specific to obstructions, such as the surface or obstruction flags.

9.7. Vent Tool

There is only one tool for drawing vents (for more information on vents, see Section 8.3). PyroSim only allows vents in an X, Y, or Z plane. Vents cannot currently be drawn off-axis like walls can.

Vents also must be attached to solid obstructions (at least one grid cell thick). This is easily accomplished by drawing the vent in the 3D View (see Section 9.4).

To draw a vent, perform the following:

9.8. Solution Mesh Tool

Solution meshes can also be drawn in PyroSim with the Solution Mesh Tool () as shown in Figure 85.

The solution mesh tool has the following tool properties:

Two types of drawn meshes

To draw a solution mesh, perform the following:

9.9. Mesh Splitter Tool

Solution meshes can be easily split into two or more sub-meshes by using the Mesh Splitter Tool ().

To split one or more meshes, perform the following:

9.10. Device Tool

PyroSim allows point devices to be drawn with the Device Tool (), for more information on devices, Chapter 15.

The device tool has the following properties:

To draw a device, perform the following:

If it is a solid-phase device, the device’s location will snap directly to the point under the cursor if one is found. This makes it trivial to attach a solid-phase device to an obstruction. If the device is a gas-phase device, however, the device’s location will be projected to the plane as set in the device tool properties as shown in Figure 89. This makes it easy to draw devices at a specific height above the floor. This behavior can be overridden for either type of device by selecting Lock Z to [V] (where V is the drawing plane) or Lock Z to Snap Location in the tool’s right-click menu. Lock Z to [V] is the automatic behavior for gas-phase devices and Lock Z to Snap Location is the automatic behavior for solid-phase devices.

9.11. Planar Slice Tool

Planar slices, as discussed in Section 18.2 can be drawn with the planar slice tool ().

To do so, perform the following:

The slice plane can be changed through the right-click menu, by click-dragging the left mouse button, or by pressing CTRL on the keyboard to cycle through the options.

9.12. HVAC Node Tool

HVAC nodes as discussed in Section 17.2, can be drawn with the HVAC Node Tool ().

To do so, perform the following:

9.13. HVAC Duct Tool

PyroSim allows HVAC ducts to be drawn with the HVAC Duct Tool ().

To do so, perform the following:

9.14. Other Box Drawing Tools

PyroSim can also be used to draw:

Init Regions (Section 19.1.4) with the Init Region Tool.

Particle Clouds (Section 14.6) with the Particle Cloud Tool.

3D Slices (Section 18.3) with the 3D Slices tool.

These tools draw axis-aligned boxes like the Solution Mesh Tool, so they behave similarly. They all have the following drawing properties:

To draw one of these objects, perform the following:

9.15. Other Point Drawing Tools

Single Particles (Chapter 14) with the Particles at a Point Tool.

Pressure Zones with the with the Zone Tool.

These tools draw points like the Device Tool, so the they behave similarly. They all have the following drawing property:

To draw one of these objects, perform the following:

9.16. Editing Objects

Nearly all geometric objects can also be graphically edited in the 3D or 2D View with the Select/Manipulate Tool ().

Editing is performed through an object’s editing handles. Handles appear on an object either as a blue dot as shown in Figure 93 or a face with a different color. The dots indicate a point that can be moved in either two or three dimensions. A discolored face indicates that a face can be moved or extruded along a line.

To graphically edit an object, perform the following:

9.17. Transforming Objects

PyroSim provides a variety of tools to transform geometry objects. With the transform tools, users can move, rotate, and mirror objects.

9.17.2. Move Tool

This tool allows the user to move selected objects to a new location as shown in Figure 95, or to create and move a copy of the selected objects.

To use this tool, perform the following:

1. Select the desired objects to move from any of the views.
2. Select the Move Tool () from the drawing toolbar.
3. Use Click-drag Mode or Multi-click Mode to draw two points defining the movement vector.

9.17.3. Rotate Tool

This tool allows the user to rotate selected objects as shown in Rotating an object with the Rotate Tool, or to create and rotate a copy of the selected objects.

To use this tool, perform the following:

1. Select the desired objects to rotate from any of the views.
2. Select the Rotate Tool () from the drawing toolbar.
3. Single-click to specify the rotation center (Figure 96).
4. Single-click another point to define a reference vector from the first point to the second point (Figure 97). This reference vector is what the angle is based from.
5. Single-click a third point to define the angle vector from the first point to the third point (Figure 98).

The selected objects will be rotated by the angle between the reference and angle vectors.

The following defines the axis about which objects are rotated for each view:

• 3D View: Z axis
• Top View: Z axis
• Front View: -Y axis
• Side View: -X axis

Rotating an object with the Rotate Tool

9.17.4. Mirror Tool

The mirror tool allows selected objects to be mirrored across a plane as shown in Mirroring an object using the Mirror Tool, or to create a mirrored copy of the selected objects.

To use the mirror tool, perform the following:

1. Select the desired objects to mirror from any view.
2. Select the Mirror Tool () from the drawing toolbar.
3. Use Click-drag Mode or Multi-click Mode to define two points that create a plane about which the selected objects are mirrored (Figure 100).

Mirroring an object using the Mirror Tool

9.18. Painting Obstructions and Vents

PyroSim provides tools to paint obstructions and vents with a surface and/or color. A user can also use a picking tool to pick the surface and/or color used to draw new obstructions or vents or to perform painting.

9.18.1. Paint Tool

A user can use the Paint Tool () to paint the faces of obstructions and vents a specific surface and/or color.

The Paint Tool has the following tool properties:

Apply Surface

Specifies whether to paint faces with surfaces and which surface to use.

Apply Color

Specifies whether to paint faces with a specific color and which color to use.

These painting options can also be cycled by pressing CTRL on the keyboard or through the tool’s right-click menu. The right-click menu also allows quick selection of a surface in the model or recently-used color.

To paint faces with the paint tool, perform the following:

1. Select the Paint Tool () from the drawing toolbar.
2. Hover the cursor over the desired face to paint. If the face can be painted with the current surface/color, the face with highlight yellow as shown in Figure 101.
3. Either single-click the face to paint only that face, or click-drag the left mouse button to paint all faces the cursor moves over. Hold SHIFT on the keyboard while painting to paint all the faces of the object rather than just one face.

9.19. Measuring Length/Distance

PyroSim provides a Measure Tool () to measure distances in the model.

To measure a distance, perform the following:

10.1. Curved Walls

While PyroSim’s tools do not explicitly produce curved walls, they can approximate them using any of the following techniques:

In all of the following examples, we will use a background image as a pattern to draw against. While this is not required, it makes creating curved surfaces much easier and one of the strengths of PyroSim is that it allows you to sketch geometry directly on top of building design images. The background image we will be using is shown in Figure 103.

For simplicity, we will assume that horizontal distance across the entire image is 50 feet, and we will place the origin of the model at the lower-left corner of the room shown in the image. The brightness of the image will be set to 50%. The Configure Background Image dialog shown in Figure 104 illustrates these settings.

10.1.1. Using the Wall Tool

To create a curved wall section from wall segments, you can follow these steps:

1. Click the 2D View tab, and select the Draw Wall Obstruction () tool.
2. Turn off grid snapping. In the View menu, click Disable Grid Snapping.
3. Position the cursor at the beginning of the curve where you want to place the first wall segment.
4. Use Multi-click Mode to click several points along the curve. More points will create a smoother curve.
5. Right-click in the 2D View and select Finish to finish drawing the wall.

This is the fastest way to create smooth curves in PyroSim. PyroSim will convert the curved walls to blocks before running the FDS simulation. While smaller segments will make the wall look better in PyroSim, placement of obstructions generated for FDS depends on the resolution of your mesh. A curved wall drawn with three different segment lengths created with this technique are shown below.

A curved wall drawn with three different segment lengths

Using extremely short line segments will probably not be of any benefit unless you also use very small mesh cells.

10.1.2. Using the Block Tool

To create a curved wall section from blocks, you can follow these steps:

1. Create a mesh. This example uses a 50.0 ft x 50.0 ft mesh with 1 ft mesh cells.
2. Click the 2D View tab, and select the Block Obstruction Tool ().
3. Turn grid snapping on. If snapping is off: in the View menu, click Snap to Model Grid.
4. Click each cell along the curved wall to place the necessary blocks.

This technique forces you to convert the curve to blocks manually, but the advantage is you know exactly what geometry will be generated for FDS. If you have a high resolution mesh, it may be useful to drag the mouse and "paint" the curve rather than clicking individual blocks. The example curved wall is shown in Figure 108.

10.1.3. Rotating an Object

To create curved objects using the rotation technique, you must place an initial segment, then perform a rotate operation about the center point of your desired curve.

This process is illustrated in the following steps:

1. Click the 2D View tab, and select the Wall Obstruction Tool ().
2. Turn off grid snapping. If snapping is on: in the View menu, click Disable Grid Snapping.
3. Create an initial wall segment somewhere on the curve.
4. In the Model menu, click Rotate.
5. Select the Copy mode.
6. Specify the necessary parameters for the rotation operation. In this example, the Number of Copies is 15, the Angle is 6.0 degrees, and the Base Point is: x=32.0 feet, y=16.5 feet.
7. Click Preview to verify that the settings are correct, then click OK.

The curve for this example is shown in Figure 109.

If we would have created 60 copies instead of 15 this procedure would have created a cylinder. While complicated, the rotation approach is the most effective at creating complex symmetrical geometry.

10.2. Trusses

Trusses can be created by drawing a single truss out of slab obstructions and slab holes, then replicating that truss as many times as needed as shown in Figure 110.

The following steps show how to create the trusses for an example roof.

10.3. Roofs

You can quickly add a roof to the model using the Slab Obstruction Tool ().

The following steps show how to add a roof to the previous truss example.

The resulting roof section is shown in Figure 111.

The extruded polygon tool can be used to create obstructions with any number of boundary points (triangles, quads, etc).

10.4. Stairs

Users can create simple stairways by placing the initial stair, then using the move operation. This section will present a simple example to illustrate the approach.

We will create a 10 step stairway. Each step will have a 7 inch rise (0.58 feet), and a 10 inch (0.83 feet) run. The stairway itself will be 24 inches (2.0 feet) wide. To keep things as simple as possible, we will construct the stairway in an empty model.

The stairway generated in this example is shown in Figure 112.

11.1. Selection

PyroSim relies heavily on the idea of selected objects. For almost all operations, the user first selects an object(s) and then changes the selected object(s). The Selection Tool () is used to select objects.

Once objects have been selected, the user can modify the object using the menus.

Selection can be made in any of the views using the Selection tool. Multiple objects can be selected using the Ctrl key or click and drag to define a box. In the Navigation View, the Shift key can be used to select a consecutive list of objects.

11.2. Context Menus

A right-click on a selection displays a context menu. This menu includes the most common options for working with the object. The user may also right-click on individual objects for immediate display of the context menu.

11.3. Undo/Redo

All geometric changes to the model can be undone and redone using the Undo () and Redo () buttons, as well as Ctrl+Z and Ctrl+Y, respectively.

11.4. Copy/Paste

Select an object to copy, then either use Ctrl+C or Edit→Copy to copy. Alternately, right-click on an object to display the context menu with Copy.

Either use Ctrl+V or Edit→Paste to paste a copy of the object. Alternately, right-click on an object to display the context menu with Paste.

11.5. Double-Click to Edit

Double-clicking on an object opens the appropriate dialog for editing the object properties.

11.6. Move Dialog

The Move dialog can be used to both move an object and to create copies of an object, each offset in space.

To move an object in this manner, perform the following:

The Mode selects either the option to move only the selected object or to create copies of the object and move them. The Offset parameters indicate the increment to move or offset the copies.

To preview the changes without applying them, click Preview. To apply the changes and close the dialog, click OK. To cancel the changes instead, click Cancel.

11.7. Mirror Dialog

The Mirror dialog can be used to mirror an object about a plane or planes or create a mirrored copy of an object. To mirror an object in this manner, perform the following:

The Mode selects either the option to mirror only the selected object or to create a mirrored copy of the object. The Mirror Plane(s) define planes normal to the X, Y, and Z axes about which the object will be mirrored. The Use Center button can be used to fill the Mirror Plane data with the center coordinates of the selected objects.

To preview the changes without applying them, click Preview. To apply the changes and close the dialog, click OK. To cancel the changes instead, click Cancel.

11.8. Scale Dialog

The Scale dialog can be used to change the size of an object or create scaled copies of an object. To scale an object, perform the following:

The Mode selects either the option to scale only the selected object or to create multiple scaled copies of the object. The Scale values define the scale factors in the X, Y, and Z directions. The Base Point defines the point about which the scaling will be performed. The Use Center button can be used to fill the Base Point data with the center coordinates of the selected objects.

To preview the changes without applying them, click Preview. To apply the changes and close the dialog, click OK. To cancel the changes instead, click Cancel.

11.9. Rotate Dialog

The Rotate dialog can be used to rotate an object or to create rotated copies of an object. To rotate an object, perform the following:

The Mode selects either the option to rotate only the selected object or to create multiple rotated copies of the object. The Rotation values allow the user to select the axis about which the rotation will be made and the angle is the rotation angle (counter-clockwise is positive). The Base Point defines the point about which the rotation will be performed. The Use Center button can be used to fill the Base Point data with the center coordinates of the selected objects.

To preview the changes without applying them, click Preview. To apply the changes and close the dialog, click OK. To cancel the changes instead, click Cancel.

11.10. Object Visibility

Often it is desirable to turn off the display of selected objects, for example, to hide a roof of a building in order to visualize the interior. In any of the views, right-click on a selection to obtain the following options:

12.1. Primitive Species

Primitive species can be tracked individually, or as a component of a more complex lumped species.

To edit primitive species:

12.2. Lumped Species

Species mixtures can be defined as a mixture of any number of primitive species. Because all species in the simulation must be tracked by a transport equation, a lumped species can be used to save on simulation time.

To create a lumped species:

To edit the lumped species:

When using lumped species, it is recommended that certain actions be taken to reduce the complexity of the simulation.

To save on simulation time:

Doing this check for all primitive species will reduce the number of transport equations solved by the simulator, and save significant time on the simulation.

13.1. Defining the Combustion Reaction

PyroSim supports the "simple chemistry" combustion model in FDS that considers a single fuel species composed of \(C\), \(H\), \(O\), and \(N\) that reacts with oxygen in one mixing-controlled step to form \(H_{2}O\), \(CO_{2}\), \(Soot\), and \(CO\) (see Chapter 12 in the FDS User Guide).

To create a reaction:

FDS will use the chemical formula of the fuel along with the yields of \(CO\) and \(Soot\), and the volume fraction of hydrogen in the soot to calculate the stoichiometric coefficients for the reaction. Details of the reaction are output by FDS in the *.out file written during execution.

13.2. Custom Smoke

PyroSim supports the custom smoke features available in FDS. To create custom smoke, first define an species with the desired mass extinction coefficient. This "smoke" species can then be injected into the domain like any other species. Smoke detectors can also detect this smoke species if it is selected under the smoke detector’s model, which can be edited under Edit Smoke Detector Models. on the Devices menu. Finally, if the Results should track this species as smoke, go to the Analysis menu, select Simulation Parameters. and on the Output tab select the mass fraction quantity of the desired species from the Smoke Quantity drop-down box. Note that in addition to specifying the mass fraction of a species, the mass fraction of any mixture fraction species can also be selected for smoke display, including the mass fraction of oxygen, water vapor, and the other species specified in the gas-phase reaction.

14.1. Liquid Droplets

Evaporating liquid droplets can be used with sprinkler spray models and nozzles to customize the spray. They can also be used in particle clouds and surface types that support particle injection.

14.2. Solid Particles

PyroSim provides basic support for specifying solid particles. A solid particle must reference a surface, from which it derives its thermophysical and geometric parameters. A solid particle can be used to model various heat transfer, drag, and vegetation applications. Most of the parameters unique to solid particles must be defined on the Advanced Panel, see Chapter 22.

14.3. Massless Tracers

Massless tracer particles can be used to track air flow within a simulation. They can be used with the particle injection feature of the Burner, Heater/Cooler, Blower, and Layered surface types. They can also be used in particle clouds.

By default, PyroSim provides a black, massless tracer particle called Tracer. To use a custom tracer particle in your simulation, you can modify the parameters of this default particle to suit your needs, or you can create a new particle.

The tracer particle properties are as follows:

14.4. Activation

Normally, the insertion of particles into the domain is controlled by the surface or object emitting them, such as by a fan or supply surface or a particle cloud. Alternatively, the insertion of particles can be controlled by a device or other control logic. For more information on controls, see Chapter 16.

14.5. Global Parameters

There are two global options relating to particles in the Simulation Parameters dialog. The first option, Droplets Disappear at Floor, can be used to prevent droplets from gathering on the floor of the simulation area. The default value for this option is ON. The second option, Max Particles per Mesh, can be used to set an upper limit on the number of particles allowed in any simulation mesh.

14.6. Particle Clouds

Particle Clouds provide a way to insert particles into the simulation either in a box-shaped region or at a specific point. Particles can either exist at the start of the FDS simulation or can be inserted periodically.

To create a particle cloud, on the Model menu, click either New Particle Cloud. to create a region of particles or New Particle Location. to specify a specific point for the particles. This will show the particle cloud dialog as in Figure 117.

Particle clouds have the following properties:

The geometry properties, including the size and location of the volume or the point location can be specified on the Geometry tab.

Press OK to create the new particle cloud. It will appear as a translucent box or a point in the 3D and 2D Views.

15.1. Aspiration Detection System

An aspiration detection system groups together a series of soot measurement devices. An aspiration system consists of a sampling pipe network that draws air from a series of locations to a central point where an obscuration measurement is made. To define such a system in FDS, you must provide the sampling locations, sampling flow rates, the transport time from each sampling location, and if an alarm output is desired, the overall obscuration setpoint.

To define the soot measurement devices:

To define the aspiration detection system:

Supply the following information for the aspiration detection system, Figure 118.

The output of the aspiration detection system will be the combined obscuration.

15.2. Gas or Solid Phase Device

Simple gas phase and solid phase devices can be used to measure quantities in the gas or solid phase. To define a measurement device, on the Devices menu, click New Gas-phase Device or New Solid-phase Device.

The device properties are:

15.3. Thermocouple

To create a thermocouple, on the Devices menu, click New Thermocouple.

The thermocouple properties are:

The output of the thermocouple is the temperature of the thermocouple itself, which is usually close to the gas temperature, but not always, since radiation is included in the calculation of thermocouple temperature.

15.4. Flow Measurement

The flow measurement device can be used to measure a flow quantity through an area. To create a flow measuring device, on the Devices menu, click New Flow Measuring Device.

The flow measurement device properties are:

The output will be the total flow through the defined area.

15.5. Heat Release Rate Device

The heat release rate device measures the heat release rate within a volume. To define a heat release rate device, on the Devices menu, click New Heat Release Rate Device.

The heat release rate device properties are:

The output will be the total heat release rate within the volume.

15.6. Layer Zoning Device

There is often the need to estimate the location of the interface between the hot, smoke-laden upper layer and the cooler lower layer in a burning compartment. Relatively simple fire models, often referred to as two-zone models, compute this quantity directly, along with the average temperature of the upper and lower layers. In a computational fluid dynamics (CFD) model like FDS, there are not two distinct zones, but rather a continuous profile of temperature. FDS uses an algorithm based on integration along a line to estimate the layer height and the average upper and lower layer temperatures. To define a layer zoning device, on the Devices menu, click New Layer Zoning Device.

The layer zoning device properties are:

The output will be the quantities selected.

15.7. Path Obscuration (Beam Detector) Device

A beam detector measures the total obscuration between points. To define a beam detector device, on the Devices menu, click New Beam Detector Device.

The path obscuration device properties are:

The output will be the percent obscuration along the path.

15.8. Heat Detector

A heat detector measures the temperature at a location using a Response Time Index model. To define a heat detector device, on the Devices menu, click New Heat Detector.

The heat detector device properties are:

The output will be the heat detector temperature.

15.9. Smoke Detector

A smoke detector measures obscuration at a point with two characteristic fill-in or "lag" times. To define a smoke detector, on the Devices menu, click New Smoke Detector.

The smoke detector device properties are:

The output will be the percent obscuration per meter.

15.10. Sprinkler

Sprinklers can spray water or fuel into the model. To define a sprinkler:

The sprinkler properties are:

15.11. Nozzle

Nozzles are very much like sprinklers, only they do not activate based on the standard RTI model. They can be set to activate by custom control logic.

16.1. Activation Control Types

PyroSim allows the creation of three unique control types. When creating a new Activation Control, you may select from one of the following:

16.2. Creating Activation Controls

Creating controls in PyroSim takes 3 steps:

After selecting an input type and an action, a pattern (in sentence form) for describing the control logic will appear in the dialog. Some key words and numbers will be drawn in blue and underlined. Any blue text can be clicked to modify the behavior of the specific control.

Figure 122 shows the selector popup for objects. Objects are selected by name. To quickly find objects in the selector popup, you can type the first few letters of the object’s name.

Activation controls are stored separately from specific geometric objects. This makes it possible to bind an object to a control after it has been created. You can use the Activation box in an object’s properties editor to bind that object to an existing activation control, or even create a new control directly. Figure 123 shows the activation control in the object properties dialog for a hole.

Once a control has been bound to an object (or objects) any objects linked to that control will show a text description of the control in their properties editor. This text will be shown in blue and underlined and can be clicked to edit the activation control. Changes made to the activation control will impact all referencing objects.

16.3. Time-based Input

To create or remove an object at a specific time, select Time for the Input Type in the Activation Controls dialog. When using time as the input, objects can be created at a specific time, removed at a specific time, or be created and removed periodically throughout the simulation. To create or remove the objects once, select Create/Activate or Remove/Deactivate under the Action to Perform. To create/remove the object periodically, select Multiple under the Action to Perform. When performing multiple timed events, the creation and removal and times at which they occur are specified in the table at the bottom of the dialog. The create and remove events should alternate as time increases.

16.4. Detector-based Input

To create or remove some objects based on a device in the model, the device or math operation must first have a setpoint enabled.

To specify a device setpoint, perform the following:

Once the desired devices have been given a setpoint, they can be used as inputs to the control logic expression. Now in the Activation Controls dialog, select Detector as the Input Type. The detector can be used to Create/Activate or Remove/Deactivate the desired objects when the detector either activates or deactivates. If more than one detector is to be used to activate the objects, the descriptive sentence can be used to decide if the objects should trigger when any, all, or a certain number of the devices activate.

16.5. Deadband-based Input

To create or remove an object according to bounding setpoints on device or math operation, select Deadband Control under the Input Type. Unlike Detector-based inputs, a Deadband-based control does not require a setpoint. The descriptive sentence will guide the user towards selecting an upper and a lower range at which the controlled objects will turn on or off.

16.6. Manual-based Input

Selecting Manual for the Input Type allows you to enter the exact CTRL record to be managed by the control. After defining a valid CTRL record in the text editor, the descriptive sentence can be used to specify the objects managed by the control.

16.7. Custom Controls

Custom controls allow objects to be created and removed periodically according to a table of setpoints. Use the Function Input combobox to specify either Time or a device as the input to the control. The table can then be used to specify multiple values at which the logic signal switches and the managed objects are created or removed. The create and remove events should alternate as values in the left hand side of the table increase.

16.8. Mathematical Controls

Mathematical controls apply simple math operations on the selected input signals. Input signals may be any of Time, the output value of a device, a constant value, or the output of another Mathematical control.

The following operations use a single value as an input: Exponential, Logarithm, Cosine, Sine, Arccosine, Arcsine, Arctangent.

The following operations use a single value in addition to specialized parameters: PID, Percentile.

The following operations use two values as inputs: Subtract, Multiply, Divide, Power.

The following operations may use many values as inputs: Sum, Maximum, Minimum.

To use a Mathematical control as an input to a detector, perform the following:

17.1. HVAC Duct

A duct is required for any HVAC system. At a basic level, a duct represents the joining of two HVAC Nodes.

To define an HVAC Duct:

You can now edit the duct:

17.2. HVAC Node

An HVAC Node represents a either a joining of two or more HVAC Ducts, or the meeting point between a duct and the PyroSim computational model. To create an HVAC Node:

You can now edit the node.

17.3. HVAC Fan

An HVAC Fan is used to generate airflow in a HVAC network. A fan is specified between two nodes by selecting it as the Flow Device for an HVAC Duct. Note that an HVAC Fan is a class of object, and a single fan definition can be used by any number of ducts.

To create an HVAC Fan:

17.4. HVAC Filter

An HVAC Filter is used to stop gaseous species from circulating in the HVAC system. A given filter can limit the flow of any number of valid species defined in the model. Note that an HVAC Filter is a class of object, and a single filter definition can be referenced by any number of nodes.

To create an HVAC Filter:

17.5. HVAC Aircoil

An HVAC Aircoil is a device that provides a heating or cooling element to an HVAC system. An aircoil is specified between two nodes by selecting it as the Flow Device for an HVAC Duct. Note that an HVAC Aircoil is a class of object, and a single aircoil definition can be used by any number of ducts.

To create an HVAC Aircoil:

17.6. HVAC Vents

HVAC Vents are used to represent the junction between the HVAC system and the rest of the computational model. See Section 8.3 for more information on using vents.

To define an HVAC Vent:

18.1. Solid Profiles

Solid profiles measure quantities (e.g. temperature, density) as they extend into solid objects. The output file for this measurement device will be named CHID_prof_n where CHID is the job ID and n is the index of the solid profile. This output file contains the data necessary to create an animated 2D chart of the quantity as it extends into the object over time. PyroSim does not currently support displaying this output file.

To generate solid profile output, on the Output menu, click Edit Solid Profiles.

Each solid profile requires the following parameters:

18.2. 2D Slices

2D Slices or slice planes measure gas-phase data (e.g. pressure, velocity, temperature) on an axis-aligned plane. This data can then be animated and displayed using the 3D Results (Figure 126).

To generate animated slice planes, either draw them using the drawing tools as described in Section 9.11 or on the Output menu, click 2D Slices.

Each slice plane requires the following parameters:

18.3. 3D Slices

3D Slices represent volumetric regions that measure gas-phase data (e.g. pressure, velocity, temperature). This data can then be animated and displayed using the 3D Results in several different ways, including volumetric renderings, plotting 2D slices through the data, plotting points, or creating isosurfaces, all in the 3D Results application. Figure 127 shows a volumetric rendering.

To generate animated 3D slices, either draw them using the drawing tools as described in Section 9.14 or on the Output menu, click 3D Slices.

Each 3D slice requires the following parameters:

18.4. Boundary Quantities

Boundary quantities provide a way to visualize output quantities (e.g. temperature) on the walls of every obstruction in the simulation. This data can be animated and visualized in the 3D Results (Figure 128). Since the data applies to all surfaces in the simulation, no geometric data needs to be specified.

To generate boundary quantity data, on the Output menu, click Boundary Quantities. In the Animated Boundary Quantities dialog, you can select each quantity you would like to be available for visualization.

18.5. Isosurfaces

Isosurfaces are used to plot the three dimensional contour of gas phase quantities. This data can be animated and visualized in the 3D Results (Figure 129).

To generate isosurface data, on the Output menu, click Isosurfaces, In the Animated Isosurfaces dialog, you can select each quantity you would like to be available for visualization. Then you must enter values at which to display that quantity in the Contour Values column. If you enter more than one contour value, each value must be separated by the semi-colon character (;). Once you have finished typing the value, press enter.

18.6. Plot3D Data

Plot3D is a standard file format and, like 3D slices, can be used to display 2D contours, vector plots, and isosurfaces in a volumetric region the 3D Results (Figure 131). PLOT3D output is formed of two parts: an XYZ file containing information about the structure of the mesh, and a Q file for each output time. Each Q file contains data for up to five quantities. Simulations with multiple meshes have XYZ and Q files for each mesh. The 3D Results will automatically stitch the individual Q files together to animate the results.

PLOT3D data can also be used by the Pathfinder evacuation simulation software to integrate with FDS results. To quickly select the quantities useful in Pathfinder, including the FED calculation, click the Reset button and click Pathfinder Quantities.

Enabling PLOT3D data in PyroSim will cause the XYZ file to be written. In previous versions of PyroSim, it was possible to generate PLOT3D output without writing the XYZ file. While this offered a way to save space in the simulation output, this sometimes led to errors when loading PLOT3D output without an XYZ file. Loading an old PyroSim file that includes PLOT3D output but is set not to write the XYZ file will cause the XYZ file settings to be ignored and the file will be written anyway.

18.7. Statistics

Statistics output is an extension of the devices system. You can insert a statistics gathering device and it will output data about the minimum, maximum, and average value of a particular quantity in one or more mesh. This data can then be viewed in a 2D chart using PyroSim (Figure 132).

To generate statistics data for some region, on the Output menu, click Statistics. then click New. Once a quantity is selected, some combination of the following options is available depending on whether the quantity is gas or solid-phase and what units are output by the quantity:

The output file for measurement devices will be named CHID_devc.csv where CHID is the job ID.

19.1. Simulation Parameters

Before running a simulation, FDS simulation parameters should be adjusted to fit the problem. This can include parameters such as simulation time, output quantities, environmental parameters, conversion of angled geometry to blocks, and miscellaneous simulator values.

To edit the simulation parameters, on the Analysis menu, select Simulation Parameters.

This shows the simulation parameters dialog. The parameters are split into several categories, with each category on another tab of the dialog.

19.1.1. Time

All time-related values can be entered on the Time tab as shown in Figure 133.

Start Time

A remapping of simulation time, t=0, to a different time. This is used to format the output time, and can be useful for recreation scenarios.

End Time

The ending simulation time.

Initial Time Step

Overrides the default time step.

Do not allow time step changes

Prevents FDS from dynamically altering the time step.

Do not allow time step to exceed initial

Prevents FDS from allowing the time step to go above the initial time step.

19.1.2. Output

The Output tab provides fine-grained control of how output values are recorded.

Enable 3D Smoke Visualization

Whether to show smoke in the results. If enabled, the visualization can be based on various species in the model.

Limit Text Output to 255 Columns

Limits how many columns are written to CSV output files.

Output File Write Intervals

Specifies intervals at which to write to various output files.

Limit HRR to Gas-Phase Combustion

Only the contribution from gas-phase combustion is included in the total Heat Release Rate.

19.1.3. Environment

The Environment tab enables various ambient environmental properties to be set as shown in Figure 135

A unique aspect of this tab is the specification feature for gravity. Gravity, in each of the X, Y, and Z directions, can be defined as a ramped function. This allows users to model complex behavior of gravity in tunnel or space applications where spatial or temporal variations in direction may change the magnitude vector. Each ramp can be set to vary as a function of either the position along the X direction, or time.

19.1.4. Init Regions

While the Environment tab provides control over ambient environmental conditions, different temperatures, pressures, and mass fractions of species can be specified in various sub-regions of the model by using Init Regions.

To create an Init Region, exit the Simulation Parameters dialog, and on the Model menu, choose New Init Region.

This opens the Initial Region dialog as shown in Figure 136. Specify the desired temperature, pressure, or mass fraction of species to override in the region on the General tab and enter the volume parameters on the Geometry tab. Press OK to create the Init Region.

19.1.5. Wind

Wind parameters can be specified by checking Configure Wind and then clicking the Edit button. This will open the Wind dialog as shown in Figure 137.

The Wind Profile tab provides control over how the wind speed and temperature develops as a function of the elevation. There are two options available for defining the Wind Profile, Custom and Monin-Obukhov Similarity.

The Custom Profile parameters provide fine-grained control over the initial wind speed, direction, and velocity and temperature as a function of elevation.

Initial Wind Velocity

Can be specified using three methods.

Speed and Direction

Allows the absolute speed and direction to be specified. The direction is specified as an angle where 0° indicates a northerly wind that blows from north to south. An angle of 90° indicates an easterly wind that blows from east to west.

Friction Velocity (u*)

Speed is calculated by FDS using Monin-Obukhov similarity as defined in the FDS user’s guide. Direction is explicitly stated as defined above.

UV Components

The U and V components of velocity are defined, where U corresponds to the X axis and V corresponds to the Y axis.

Z Velocity

Allows the definition of the velocity component in the Z direction.

Speed Profile

Can be used to define the wind velocity in X,Y and Z directions as a function of Elevation.

Temperature Profile

This section defines the atmospheric temperature profile for the wind.

Ground Level

The elevation in the model where the 'Ground' plane (sea-level) is located, by default, this is at Z=0.0.

Lapse Rate

Defines a constant rate at which the temperature increases or decreases with elevation.

Z Temperature Profile

Alternatively, a custom function can be specified for the temperature as a function of elevation.

If the Wind Profile is set to Monin-Obukhov Similarity as shown in Figure 138, the wind profile is specified using a set of similarity parameters as defined in the FDS User’s Guide.

Thermal Stability

Indicates the stability of the temperature with rises in elevation. This can be set to several predefined values or to a custom value.

Landscape

Indicates the type of terrain in the model. This can also be set to several pre-defined values or a custom value.

Reference Height

Defines a height at which various parameters were measured, such as the wind Speed, Friction Velocity and Scaling Potential Temperature. If the scaling potential temperature or friction velocity are unknown, they will be calculated by FDS using the speed, reference height, and landscape value.

The Speed Change over Time tab allows control over the wind velocity as a function of time. While the wind profile determines the base speed at various locations and elevations in the model, the speed change over time parameters provide multipliers that are applied to these values to vary them over time.

The Natural Wind tab provides the ability to allow wind to develop naturally by specifying pressure drops over distance. This may be useful for modeling transit tunnels.

19.1.8. Angled Geometry

PyroSim allows obstructions and holes to be drawn that are not aligned with the solution mesh needed by FDS (Figure 142). To write the FDS input file, PyroSim must convert the objects that are not immersed boundary obstructions to axis-aligned blocks, first. PyroSim will either do this automatically when the FDS input file is generated, or this can be done manually for individual objects by right-clicking the object and selecting Convert to Blocks. For more information about immersed boundary obstructions, see FDS GEOM.

The Angled Geometry tab of the simulation parameters dialog provides default parameters that control conversion of obstructions and holes into blocks for the FDS input file as shown in Figure 139.

Conversion Filtering

Controls which objects are converted into blocks.

Rasterize axis-aligned

This option forces non-GEOM objects that are axis-aligned to be rasterized.

Rasterize GEOM

Forces immersed boundary (GEOM) obstructions to be rasterized and written as OBST records rather than GEOM records. This option is only available if FDS GEOM is enabled. See FDS GEOM for more information.

Grouping

Controls how resulting objects are created after being converted to blocks. This is more relevant to manual conversion of objects to blocks.

Group blocks into composite objects [default]

For each converted object (such as a wall), creates one resulting object that is a composite of all the sub-blocks.

Create an object for each block and add to a group

Creates a new PyroSim object for each resulting block. These objects are then added to a group representing the original object.

Block Size

Controls how large resulting blocks may be, see Merging converted blocks below.

Allow resulting blocks to span multiple mesh cells [default]

Resulting adjacent blocks with the same properties are merged into one block, vastly reducing the number of produced blocks (Figure 140).

Force blocks to be no larger than one grid cell thick

Blocks will not be merged (Figure 141). This may create great numbers of blocks that will take additional memory but have the advantage of being more easily deleted.

Thickening

Controls whether objects are allowed to be thin.

Allow thin obstructions [default]

Allows objects to become thin as shown in Figure 143. This may be overridden for obstructions by turning on Thicken in the obstruction properties dialog.

Force all obstructions to be thickened

Prevents all obstructions from becoming thin (Figure 144).

Merge objects with identical properties [default=true]

Allows blocks to be merged across source objects if their resulting blocks have similar properties. For instance, if this is true and two walls are drawn with similar properties, their converted blocks will be merged into the same group or composite object. This can further reduce the number of resulting objects.

Separate disjoint objects [default=true]

Prevents objects' block from being merged if their blocks do not touch.

Ignore names while merging [default=false]

Controls whether names are considered when determining whether objects are "similar."

Merging converted blocks

Effect of thickening on converted blocks

19.1.10. Misc Tab

This tab allows some miscellaneous simulation and model properties to be set.

Default Surface Type

This specifies the surface to apply to mesh boundaries, solid objects, and vents by default.

Force the Mixture Fraction Model (If Needed)

This detects if an output quantity is being used, such as by a device,

Texture Origin

Sets the global XYZ position of all texture origin points. See Section 7.4 for more details on textures.

19.2. OpenMP Environment

As of FDS version 6.1, FDS added multithreading support using a library called OpenMP. OpenMP will automatically be used to utilize multiple processing cores, if available, during the simulation procedure. The behavior of OpenMP during an FDS simulation is not controlled by the FDS input file, but rather by environment variables.

The OpenMP environment dialog provides a way to edit the environment variables that control OpenMP (Figure 146). These settings are applied to the execution context created by PyroSim and do not alter system environment variables.

When left unset, OpenMP calculates a value (for example, 32-bit OpenMP uses 256M). Because the OpenMP’s calculated value tends to cause FDS to crash with a segmentation fault, PyroSim sets this value to 16M by default. An upper bound suggested by NIST is 200M.

19.3. Run FDS

Once you have created a fire model, you can run the simulation from within PyroSim. FDS actions can be accessed from either the Analysis menu or the main toolbar, as shown in Figure 147. To begin a simulation: on the Analysis menu, click Run FDS. or click from the main toolbar. Simulations launched in this way can use multiple OpenMP threads, but will not use multiple MPI processes.

PyroSim will create a sub-directory of the current PyroSim file to store FDS input and results. So for instance, if the PyroSim file is named C:\pyrosim_files\switchgear.psm, the results will be stored in C:\pyrosim_files\switchgear.

PyroSim will save a copy of the current PyroSim file into this directory and create the following files:

The file preferences control whether the optional files are written, see Section 2.8 for more information.

The input files will automatically be named after the PyroSim file. With the default preferences, for the "switchgear" example, the files would be switchgear.fds, switchgear.views, switchgear.pyrofloors, and switchgear.pyrogeom. All result files from FDS will also be stored in this directory.

Next, the FDS Simulation dialog shown in Figure 148 is launched. This dialog, which shows FDS progress and messages, can be minimized and you can continue using PyroSim (and even run additional simulations) while a simulation is running.

19.4. Parallel Execution

PyroSim includes support for FDS’s MPI-based multi-process execution. When running a simulation with multiple MPI processes, all of the computation within each of the meshes can take place independently. Assuming a simulation executes in t seconds using only one processor, the best possible performance improvement using n processors and n meshes is a reduction to t/n seconds.

To launch a simulation that uses multiple MPI processes:

or

Before running a parallel simulation, you may want to take into account some guidelines:

For a detailed list of suggestions and information about running FDS in parallel, please consult section 6.3.2 of the FDS Users Guide.

19.5. Cluster Execution

PyroSim supports the ability to run an FDS simulation on a network cluster using MPI. This has similar restrictions to running a parallel simulation, in that each grid is run in a separate process. The cluster may be composed of several computers, or nodes, and each node may have any number of processors.

Cluster simulations have the following configuration requirements:

To launch a cluster simulation within PyroSim:

or

This will launch the Cluster FDS Parameters dialog as shown in Figure 149.

All nodes in the cluster can be entered in the table, along with the number of processes to launch on each node.

Click the OK button to begin the simulation.

All input and output files will be stored in the same directory as the specified FDS file. In addition to the standard input files, PyroSim will also copy the appropriate FDS and MPI executables into the FDS file’s directory. This ensures that all nodes in the cluster use the same versions of FDS and MPI.

19.6. Cloud Execution

PyroSim supports the ability to run an FDS simulation in the cloud. PyroSim currently integrates with CFD FEA Service’s Cloud HPC. Users can view pricing details and register for Cloud HPC on their website.

To launch a cloud simulation within PyroSim:

This will launch the Cloud FDS Parameters dialog as shown in Figure 150.

The Cloud FDS Simulation dialog, as seen in Figure 151 has a few distinct differences from the normal FDS Simulation dialog.

After a simulation is launched in the cloud, the Cloud FDS Simulation dialog will not keep track of its status. It instead cedes to the dashboard of the Cloud Provider once the simulation has successfully been started. The simulation will continue to run, even after you close the Cloud FDS Simulation dialog. You may access the dashboard page for your simulation from the link provided in the Status field on the dialog.

The behavior of the Kill and Stop buttons may change depending on your Cloud Provider. For CFD FEA, the Kill button will wipe the simulation and not produce any results, while the Stop button will save the simulation and its results at its current step.

Users may also find links to the dashboards for the available Cloud Providers from within PyroSim:

19.7. Resuming a Simulation

If an FDS simulation has been gracefully stopped by pressing the Stop button in the simulation dialog, it can later be resumed. To do so, on the Analysis menu, click Resume FDS. This will cause an additional RESTART flag to be written to the FDS input file. When FDS detects this flag it will automatically attempt to reload the previous execution state from the hard disk and resume where it left off. If FDS is unable to load the previous execution state, it will exit with an error.

19.8. PyroGeom File

When PyroSim creates an FDS input file, it also outputs a PyroSim Geometry (.pyrogeom) file if enabled in the preferences, see Section 2.8.5. This file contains information about the scene geometry, including obstructions, vents, meshes, and other CAD data before they are converted to blocks. This allows the Results to show a detailed, animated view of the model along with FDS results.

Each object in this file is linked with the corresponding FDS blocks in the input file. This allows the Results application to show and hide the detailed objects that are activated/deactivated over time due to control logic in the FDS input file (see Chapter 16). In order to make this work correctly, however, PyroSim must perform some additional processing on the geometry, including the following:

If there are any OBST, VENT, or HOLE records in the Additional Records section of the Record View, the following message will appear in PyroSim when writing an FDS file:

This message indicates that the PyroGeom file will no longer accurately represent FDS objects as they are activated and deactivated. Instead, the PyroGeom objects will always be visible, and all obstructions have all holes subtracted from them in this view (but not in the FDS input file). Objects will no longer show and hide as they would before. Because of this, the FDS snapped obstructions are shown by default in the Results instead of the PyroGeom file.

In order to fix this issue, the OBST, VENT, and HOLE records must be moved from the Additional Records section into the PyroSim model. This can be accomplished by cutting the text of these records and pasting them into the 2D or 3D model view.

20.1. Launching Results

Results is a powerful post-processor for FDS created by Thunderhead Engineering. It allows the user to view the FDS model along with results in 3D. For Pathfinder users, it also allows the user to combine evacuation results in the same window. For more information, see the Results User’s Manual located in your PyroSim install folder or under the Help menu.

By default, if you run FDS from within PyroSim, the Results Viewer will automatically be launched at the end of the FDS run. This can be configured in the FDS Simulation dialog by checking "Show results when finished", or by going to the FDS tab in the Preferences dialog and selecting "Run Results when FDS simulation completes". Alternately, you can click () on the Analysis toolbar to launch the most recent results. You may also run the Results at any time by going to the Results menu and selecting View Results. This will prompt you to choose a Results file (.smv) to open.

20.2. Launching Smokeview

Smokeview is a post-processor for FDS supplied by NIST. It allows the user to view the FDS model along with results in 3D. The user can view animated smoke, slices, Plot3D, and various other output quantities.

If you run FDS from within PyroSim, Smokeview will not be automatically launched at the end of the FDS run. You may run Smokeview at any time by going to the Results menu and selecting Open Smokeview. This will prompt you to choose a Smokeview file to open.

20.3. Time History Results

Time history results are saved for heat detectors, thermocouples, and other fire output. After running an FDS simulation, the most recent plots can be viewed by clicking on the FDS toolbar. This will show a plot of thermal results. Device and control results may also be viewed by by clicking the down-arrow and selecting the desired plot.

Not all results are supported for viewing in PyroSim. FDS output files that are known to not display correctly in PyroSim include CHID_pressit.csv and CHID_cpu.csv. The files CHID_devc.csv, CHID_hrr.csv, and CHID_ctrl.csv are expected to work in most configurations.

Additional plots may be shown by going to the Results menu and choosing View Time History Results. A typical heat detector plot is shown in Figure 152. The user can export the image to a file.

20.4. Archiving Results

After running a simulation, the results may be archived along with the FDS and PyroSim input files. To do so, on the Results menu, click Archive FDS Results. This will show the Archive FDS Results dialog as shown in Figure 153.

Press OK to create the archive. The archive will be stored in the directory of the current PyroSim file.

20.5. Restoring Archived Results

Once results have been archived, they can be later restored. To do so, on the Results menu, click Restore FDS Results. This will show the Restore Archived Results dialog as shown in Figure 154.

21.1. Create and Manage Your Own Libraries

You can create and manage your own libraries for data that you commonly use. A library is a single file that can contain several categories of objects, such as Materials, Gas-phase Reactions, and Surfaces.

To manage your library:

After you have saved your library, you can load it into a new model and copy data from the library to your model.

21.2. Use the Library Provided with PyroSim

PyroSim includes a library of reaction and material data gathered from industry resources, the verification analyses provided with FDS, and predefined FDS values. Each of these reactions and materials has a reference in the Description that documents the source of the data. The properties in this library should be used as a starting point for your own settings, and not as a "standard" library.

It is your responsibility to verify that this data is correct and applicable to your simulation.

To import data from the PyroSim database:

21.3. Import a Material or Reaction from the FDS 4 Database

First, a caution. Version 4 of FDS provided a database that included several common materials and reactions. In version 5, the FDS developers made a conscious choice to remove material and reaction data. Many of the materials in FDS 4 were simply examples, and they were worried that users were applying them without using their own test or lab data as validation. In this section, we describe how to import the FDS 4 database, however, it is your responsibility to verify that this data is correct and applicable to your simulation.

You can convert the old FDS 4 materials and reactions for use in PyroSim 2007.

To import FDS 4 data:

22.1. Additional Records Section

There are times when PyroSim does not support an entire record. In this case, the record can be entered into the Additional Records Section of the Record View as shown in Figure 156.

When PyroSim write the FDS input file, it copies the contents of the Additional Records Section exactly at the beginning of the FDS file.

Because PyroSim performs no validation on text in this view, it is up to the user to ensure that the statements are well-formed FDS statements and that they do not conflict with any records generated by PyroSim. In addition, none of the records written in this section can be referenced by other PyroSim objects. For instance, if a SURF record is entered in this section, it cannot be referenced by an obstruction in the PyroSim user interface. The only way to do so would be to write the obstruction in the Additional Records Section as well.

Some records, such as MISC, RADI, and others that occur once in the FDS input file can be entered in the Additional Records Section even if PyroSim has generated the record already. For instance, if PyroSim generates the record, &MISC TMPA=30.0/, you can still enter another entry for MISC in the Additional Records Section, such as &MISC P_INF=2.0E5/. FDS will merge these MISC records together to form &MISC P_INF=2.0E5, TMPA=30.0/.

22.2. Advanced Parameters

Sometimes PyroSim may support a record but may not support it completely. For many of these records, including SURF, REAC, MATL, PART, TIME, DUMP, RADI, and MISC, PyroSim provides a way to enter additional fields. For Surfaces, Materials, Reactions, and Particles, there is an Advanced tab in the properties dialog where these additional fields may be entered, as shown in Figure 157. To enter additional fields for TIME, DUMP, RADI, and MISC, on the Analysis menu choose Simulation Parameters then choose the Misc. tab.

When entering additional fields, you must specify the field name and the field value. These additional fields will then be appended to the FDS record generated by PyroSim. As in the Additional Records Section, PyroSim will write these fields to the file exactly as entered in the table, so care must be taken by the user to make sure they are correct.

When PyroSim generates an FDS input file, some model objects may be ignored. PyroSim attempts to use a system of dependencies to determine whether or not a PyroSim object needs to be written out to the input file. Occasionally, this can lead to problems, especially when the Additional Records section is in use. For some objects, this default behavior can be modified by specifying that PyroSim always write the object to the input file, via the Always Write FDS Record checkbox in the Advanced tab.

23.1. How to Activate a Node-Locked License

23.1.1. Online

With the License dialog open, as shown in Figure 158, Step 1 is to click the Online button under the 'License File' option. Step 2 is to paste the activation key that you received from Thunderhead and click OK.

23.2. Floating License Server Problems

The floating license server provides an administration web service that can assist with diagnosing many floating license problems. If the license server is installed on the local machine, the license administration server can be accessed at the following web address:

http://localhost:5054

If the license server is installed on a remote machine, replace "localhost" with the name of the remote machine (i.e. the host name of the floating license server).

Once you have opened the Reprise License Server Administration page, you can use the Status commands to attempt to debug the license server problem yourself, or you can send a diagnostic report to support@thunderheadeng.com for assistance. To generate a diagnostic report:

23.3. Floating License Server Too Old, Update Required

PyroSim 2017 and newer require and updated version of the Thunderhead License Manager. You can download an updated license manager from the PyroSim download page:

https://support.thunderheadeng.com/docs/license-manager/2020-1/user-manual/

The license manager is often not installed on the same computer where PyroSim is running and instead installed on a shared server. Please review the Floating License Manager Installation guide for details on the install process.

In most cases, the newer version of the floating license manager will replace the previous version, the LIC files will be retained throughout the update process, and PyroSim will authorize against the updated server with no additional work.

23.4. Licensing/Registration Problems

If you experience trouble registering PyroSim, please contact support@thunderheadeng.com.

23.5. Video Display Problems and Crashes on Startup

PyroSim utilizes many advanced graphics card features in order to provide accelerated and enhanced display of models.

Sometimes these graphics features combined with certain display drivers can cause display issues or crashes on startup. The first step in these cases is to ensure you have the latest operating system updates and graphics drivers installed. If you do and you still have display problems or crashing on startup, you can start PyroSim in Safe Mode, which disables several graphics features. To start in Safe Mode:

If you encounter display problems or crashes, please let us know the make/model of your video card and what video driver you are using, even if Safe Mode fixes your issues. That will help us improve the software in future updates.

23.6. Memory for Large Models

When running large models, it is possible that an out of memory error will be encountered. If this occurs, you can increase the default Java heap size. In our experience, the maximum size can be specified to approximately 70% of physical memory. By default, PyroSim will specify a java heap size of 50% of physical memory.

To specify the memory, you can either run from a command line or change the Start Menu shortcut properties. To run from a command line, open a command window and then go to the PyroSim installation directory (usually C:\Program Files\PyroSim 2023). Execute PyroSim on the command line using the -JXmx argument. In this argument, the J specifies that the command will be passed along to the Java VM, not PyroSim. For example, pyrosim -JXmx1200m will request 1200 MB of memory.

To edit the PyroSim shortcut properties . Right-click on the PyroSim icon . Select the Shortcut tab . Edit the Target by adding a space and -JXmx1200m to the end of the Target.

A typical Target will then read C:\Program Files\PyroSim 2023\pyrosim.exe" -JXmx1200m.

23.7. Parallel Simulation (MPI) Problems

Microsoft Windows [Version 10.0.18363.778]
(c) 2019 Microsoft Corporation. All rights reserved.

C:\>cd "\Program Files\PyroSim {versionyear}\fds\mpi"

C:\Program Files\PyroSim {versionyear}\fds\mpi>mpiexec -remove
Account and password information removed from the Registry.

C:\Program Files\PyroSim {versionyear}\fds\mpi>mpiexec -register
account (domain\ user) [aurora\thornton]: aurora\mpi_user
password:
confirm password:
Password encrypted into the Registry.

C:\Program Files\PyroSim {versionyear}\fds\mpi>mpiexec -validate
SUCCESS

Microsoft Windows [Version 10.0.18363.778]
(c) 2019 Microsoft Corporation. All rights reserved.

C:\>cd "\Program Files\PyroSim {versionyear}\fds"

C:\Program Files\PyroSim {versionyear}\fds>fds

23.8. Additional Support Resources

PyroSim has a support forum located at https://thunderheadeng.freshdesk.com/support/discussions.

If you are unable to resolve your issues from the suggestions in the table, please contact Thunderhead Engineering Email Support.

The PyroSim software is available for download from the release notes: https://support.thunderheadeng.com/release-notes/pyrosim/

The same site provides PyroSim user manuals and example problems. Please follow the examples to become familiar with the software.

Mail should be sent to:

Thunderhead Engineering
403 Poyntz Ave. Suite B
Manhattan, KS 66502-6081
USA

A.1. Global Simulation Parameters

The following items that can be set in the Simulation Parameters dialog of PyroSim 2006 are not supported in PyroSim 2015 and will be dropped.

All other simulation parameters will be converted to PyroSim 2015 without warnings.

A.2. Sprinklers and Pipes

All correctly specified sprinkler parameters are converted without warnings. If a sprinkler has been assigned a massless particle, however, that sprinkler will be assigned a particle with parameters from the make file, and a warning will be issued.

For FDS 4 sprinkler make files, PyroSim has a robust built-in parser that can handle both simple and complex spray patterns. The only requirement is that referenced make files must exist in the fds folder in the PyroSim install directory. PyroSim 2015 ships with the make files provided by NIST for FDS 4. If a file uses another make file, place it in this directory before importing or opening the file.

If there is a dry pipe delay greater than zero, PyroSim 2015 will create a single dry pipe with that delay and attach it to all the sprinklers in the model. Note, however, that in PyroSim 2015 the water pressure is specified per sprinkler rather than per pipe. Because of this, PyroSim will not convert the dry pipe pressure specified in the pipe record, and a warning will be issued.

A.3. Reactions

To convert reaction data into a form useable by version 5 of FDS, PyroSim 2015 must reverse-engineer the fuel molecule composition based on stoichiometric coefficients. To accomplish this, PyroSim uses the equations given in section 4.4.2 of the users guide for version 4 of FDS. The result is then checked to ensure that the total molecular weight is the same as the specified molecular weight. If this check succeeds, no warning will be issued. If the test fails, PyroSim will issue a "Converted stoichiometry" warning and you must manually update reaction data to ensure accurate simulation results.

A.4. Surfaces

Some surface properties are converted with no additional input or warnings, including surface names, colors, and textures. The different surface types, however, undergo more complicated conversions. The following describes how PyroSim 2006 surface types are converted to Surfaces and Materials in PyroSim 2015:

A.5. Thermally Thin Surfaces

Unlike PyroSim 2006, PyroSim 2015 requires that every layered surface specify a thickness \(\delta\) for each layer and that materials specify density \(\rho\), specific heat, and conductivity \(C\). In PyroSim 2006, there were a number of ways for thermally thin surfaces to either specify or omit these parameters. These surfaces allowed any one or more of \(C\), \(\delta\), and \(\rho\) to be specified in addition to \(C*\delta*\rho\). PyroSim 2015 will make a best-effort calculation of missing parameters. For instance, if \(C*\delta*\rho\) is specified along with two of the parameters, the third will be calculated; however, if more than one parameter is missing, PyroSim will use defaults for up to two of the parameters and calculate the third missing one. The default thickness for thermally thin surfaces is set to 1mm. In all cases where a default number has been assumed due to a missing parameter, a warning will be shown for the parameter.

A.6. Where is the Surface Database?

PyroSim 2015 does not currently ship with a surface database, but users can still make their own. In fact, many different objects can now be put into a database including materials and surfaces, species, reactions, particles, and several more. As common surface descriptions and other of these object properties become available from reliable sources in a format supported by version 5 of FDS, PyroSim will again ship with a pre-filled database.

B.1. Global Simulation Parameters

The following items that can be set in the Simulation Parameters dialog of PyroSim 2012 are not supported in PyroSim 2015 and will be dropped.

All other simulation parameters will be converted to PyroSim 2015 without warnings.

B.2. Reactions

While most reaction data can be converted easily, FDS6 does add new requirements to specify a valid reaction. Most notable is the requirement that a Fuel Species by specified by the user. This can be either a Predefined species, a User Defined species, or a Default species. When the Default species type is used, a generic, non-editable species called REAC_FUEL is added to the list of species. This species can be used the same way any other species would be, but its fields cannot be edited. All reactions defined in PyroSim 2012 or older automatically use the Default fuel type.

It should also be noted that in FDS6 based PyroSim versions, it is required that a reaction be active in order to simulate a fire. To make this transition easier, PyroSim automatically adds a reaction called PROPANE_REAC when converting PyroSim files that do not specify a reaction. The PROPANE_REAC attempts to mimic the default propane reaction that is used in FDS5.

The following items will be dropped from the Reaction record:

B.3. Surfaces

Surfaces have undergone relatively few changes in from PyroSim 2012 to PyroSim 2015. However, a number of items are no longer supported in the new version.

The following records will be dropped:

B.4. Particles

Unlike PyroSim 2006, PyroSim 2007 requires that every layered surface specify a thickness Delta (\(\delta\)) for each layer and that materials specify density Rho (\(\rho\)), specific heat, and conductivity (\(C\)). In PyroSim 2006, there were a number of ways for thermally thin surfaces to either specify or omit these parameters. These surfaces allowed any one or more of \(C\), \(\delta\), and \(\rho\) to be specified in addition to \(C*\delta*\rho\). PyroSim 2007 will make a best-effort calculation of missing parameters. For instance, if \(C*\delta*\rho\) is specified along with two of the parameters, the third will be calculated; however, if more than one parameter is missing, PyroSim will use defaults for up to two of the parameters and calculate the third missing one. The default thickness for thermally thin surfaces is set to 1mm. In all cases where a default number has been assumed due to a missing parameter, a warning will be shown for the parameter.

In PyroSim 2015, the interaction between particles and species has changed significantly. In PyroSim 2012, a particle could be attributed various Thermal Properties and Fuel Properties. Most of these variables have since been moved to the species object.

To handle converting legacy files, PyroSim 2015 generates a new species based on the Thermal / Fuel Properties of the legacy particle. This species is then assigned under the Liquid tab of the PyroSim 2015 particle.

The following is a list of items which are applied to the generated species:

Some items are not convertible. The following are dropped from the record:

All other items are converted properly.