Scenarios

3.1. Opening the Edit Scenarios Dialog

To begin, open Getting Started - Scenarios.psm linked at the top of this tutorial. To open the Edit Scenarios dialog, click the Edit Scenarios icon on the main toolbar. Figure 1 shows the dialog that should appear.

The tree on the left-hand side of the dialog shows all of the scenarios defined in this model. By default, there is only one scenario defined, and it is automatically selected when the dialog is opened for the first time.

At the top of the right-hand side of the dialog, the Scenario ID of the selected scenario is listed and below, the Description for the selected scenario is given. The Description the text field can be edited to help manage and keep notes about the specifics of each scenario.

Below the Description field is the Disabled Objects text box. This text box will list all of the objects that are disabled for the selected scenario. This text box will be covered in more depth later in this tutorial.

3.2. Creating New scenarios

To create new scenarios, simply click the New button in the Edit Scenarios dialog. For this example:

The above steps will have created the Ground Floor scenario in the Edit Scenarios dialog tree. Repeat steps 1-4, this time naming the new scenario Second Floor.

Once the two new scenarios are created, select the Default scenario, and click Delete. Now, the Ground Floor and Second Floor scenarios should be the only two scenarios in the tree, shown in Figure 2.

With the Edit Scenarios dialog still open, select the Ground Floor scenario, and then click Activate. In the PyroSim menu bar, the Ground Floor scenario has been activated in the Active Scenario dropdown, located next to the Edit Scenarios icon and shown in Figure 3. The scenario dropdown can be used to select which scenario is active without opening the Edit Scenarios dialog.

In the Description field of the Ground Floor scenario, enter the following description, then click Apply to save the changes:

Likewise, in the Description field of the Second Floor scenario, enter the following description, then click Apply to save the changes:

4.1. Disabling objects

With the second floor objects disabled, the Ground Floor scenario is now different than the Second Floor scenario. In the Active Scenario dropdown, switch between the two scenarios. The second floor objects are still active and visible in the Second Floor scenario, but not in the Ground Floor scenario.

To finalize the two scenarios, switch to the Second Floor Scenario, and disable the Burner Vent - Ground, SD - Ground, and Thermocouple - Ground objects.

4.2. Scenario Overview

To get an overview of the two scenarios, open the Edit Scenarios dialog by clicking the Edit Scenarios icon. In the scenarios tree, select the Ground Floor scenario. The Disabled Objects text box, mentioned in Section 3.1, now shows all of the objects that were disabled in this scenario. Selecting the Second Floor scenario in the scenario tree will update the list to represent only the objects disabled in the Second Floor scenario.

4.3. Updating Object Properties

Currently, scenarios only explicitly track the enabling and disabling of objects. To modify an object parameter in a scenario, the object must be duplicated, the parameter in the duplicate must be modified, and the original object must be disabled in the scenario. The following will walk through a brief example of this by adjusting the heat release rate of the fire in the Second Floor scenario.

The Second Floor scenario now has a new heat release rate of \(2000 kW\) for the fire. This process can be replicated with any number of other object properties, it is not limited to just HRRPUA or vents.

5.1. Exporting the Scenarios batch script

To export the scenarios batch script:

This batch script will run all of the scenarios PyroSim just generated and saved. The individual FDS and other configuration files are located inside of folders in the same directory as the batch file.

5.2. Viewing and Editing the Batch Script

In the Windows Explorer, right-click the batch script and click Edit. A notepad window should pop-up and show a script similar to the following:

@SETLOCAL
@ECHO off
@ECHO [%~n0] Beginning at %time%

SET PATH=
SET PATH=%PATH%;C:\Program Files\PyroSim 2020\fds
SET PATH=%PATH%;C:\Program Files\PyroSim 2020\fds\mpi
SET PATH=%PATH%;C:\WINDOWS
SET PATH=%PATH%;C:\WINDOWS\system32

SET I_MPI_WAIT_MODE=1
SET OMP_NUM_THREADS=1
SET OMP_STACKSIZE=16M


ECHO [%~n0] Scenario "Ground Floor" beginning at %time%
PUSHD Getting_Started_-_Scenarios-Ground_Floor
runfds.exe mpiexec.exe -n 1 -localonly fds.exe Getting_Started_-_Scenarios.fds
POPD

ECHO [%~n0] Scenario "Second Floor" beginning at %time%
PUSHD Getting_Started_-_Scenarios-Second_Floor
runfds.exe mpiexec.exe -n 1 -localonly fds.exe Getting_Started_-_Scenarios.fds
POPD

ECHO [%~n0] Completed at %time%
pause

The first 11 lines of the batch script set some environment variables for FDS and MPI, and print some output to the shell window when it is run. To learn more about the MPI variables and what they do, see this post.

The rest of the code handles running each scenario. The script moves the working directory into the scenario folders, runs each scenario, then move back to the root directory of the project. The variables in this script can be modified to improve simulation time according to the post above and the FDS User Guide.

By default, the batch file is configured to run each simulation in sequence using a configuration largely identical to PyroSim’s Run Parallel command. It uses the program runfds.exe, which is a convenience application bundled with PyroSim that launches fds.exe with "below normal" operating system priority – a quality of life feature for users that continue using their PC while the simulations are running with negligible performance impact for unattended runs.

5.3. Running the batch script

To run the batch script, double click the batch script in the Windows Explorer, or run it via command line. This will open a new command prompt window and begin the simulations. When the simulations are complete, view the 3D results by opening the *.smv files in the individual scenario directories created by PyroSim above.