[User Tip]Parametric Studies Using SimManager

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Parametric studies are an important aspect of CFD analysis. Parametric studies are used to perform trend base analyses, optimize the deign of a device, and/or to study the affect of different parameters on a process (What if? type analysis). A parametric study is a series of simulations where one or more parameters of the problem are varied to investigate the sensitivity of the solution to the parameters.

Typically, you would perform the grid generation, set up the solver parameters, run the simulation and analyze/visualize the results. Based on the results, you may change certain solver parameters, certain grid parameters, and/or make a change to the geometry and rerun the case. This process may need to be repeated several times. This process can be controlled from one central application called SimManager.

With SimManager, you can perform automated parametric studies using the Parametric Wizard. The wizard allows you to specify the set of parameters you would like to vary and the values to use for the parameters. Boundary conditions, such as velocity, pressure, etc., Volume conditions, such as thermal conductivity, specific heat, etc., and geometric parameters can all be parameters in SimManager.

Consider a case of laminar flow over a backward facing step geometry as shown in the sketch. The goal of the parametric study is to investigate the laminar flow characteristics by varying the inlet velocity (0.1m/s, 0.2 m/s, 0.3 m/s) at steady state.

SimManager will create three different DTF files for each of the U-velocity values specified. Once the DTF file is created, the solver will run the simulation. This will be repeated for the number of cases specified. In the figures below, you can see the results for the three cases in this example.

SimManager is a great tool, which allows you to automate the process of running parametric simulations. Try using SimManager the next time you need to run parametric simulations.

To learn more about how to run a parametric analysis in SimManager, please read the remainder of the note. Click here to get the files used in this user tip.

If you have any questions about this feature or would like us to discuss some other topic in the future, please let us know.

Kartik Shah
Senior Applications Engineer
ESI CFD Customer Support

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Setup

1. Create geometry and grid using CFD-GEOM and save the DTF file (backstep.DTF). (Please Note: If you want to change the geometric parameter, you need to have a corresponding python script file, which you can generate using journaling option in CFD-GEOM or create using python scripting. In the script file, you must create a parameter for the geometric dimension to be studied.)
2. Open the DTF file (backstep.DTF) in CFD-ACE-GUI and setup your problem once. It's a good idea to perform a test run to make sure the setup is correct before submitting the jog through SimManager.
3. Open SimManager and select Tools -> Parametric Study Wizard, as shown in Figure 1.
   
   Figure 1. Parametric Study Wizard

   This opens the Parametric Study wizard as shown in Figure 2.

   Figure 2. Select the DTF file to use in the parametric study
   
4. Select the DTF (backstep.DTF) file you want to use for the parametric study. Click on the "Browse" button to select the DTF file.

   Note: Activate the "Use CFD-GEOM Parameters" button only if you wish to do geometric parametric studies. If you click that, then you have to browse for the corresponding Python script file for the geometry.

5. Click on the "Import Table of Cases" pull down menu and select the "Create Table of Cases" option as shown in Figure 3.
   
   Figure 3. Creating the number of cases to run
   
   
6. As we are going to change the "U" velocity at Inlet boundary for 3 different values:
7. • Type '3' for number of cases
   • Click on 'Specify' and select "U-Value" for Inlet Boundary and click "Select" as shown in Figure 4.
     
     Figure 4. Select "U-Value" as the parametric variable

Please note the following:

• You can change volume condition parameters along with BC parameters by clicking on "Add Parameter" button and selecting the "VC" option.
• In order to change the parameters for any Boundary or Volume, you have to provide unique names to the boundary or volume (apart form default "NoName") in order for it to be recognized in SimManager.

7. Click "Next" to go to next page and click "Next" once more. Fill out the table with the velocity values and click the "RUN ALL" button as shown in Figure 5. Figure 5. Select "Run All" to run all of the cases