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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
Setup
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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.)
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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.
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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
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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.
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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
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As we are going to change the "U" velocity at Inlet
boundary for 3 different values:
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Type '3' for number of cases
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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:
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You can change volume condition parameters along with
BC parameters by clicking on "Add Parameter" button
and selecting the "VC" option.
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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.
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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
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