Download Files

On Youtube

Watch it on Youtube Video

Converting Meshes to Wildkatze Format

We start with mesh in Fluent format. It is also possible to convert the mesh from Starccm’s ccm and openFoam format. Here we have TriVortexShed.msh file in Fluent format.

To convert we use fluent2bmsh command where the meshFile is without .msh extension. So we have

 
 fluent2bmsh TriVortexShed
 

This converts the mesh into .info.bmsh and .bmsh files.

We can check what .info.bmsh contains.

It is importan to note that one can change the boundary types here to Wall, Inlet, Outlet and Symmetry.
Also one can change Fluid to Solid types for Conjugated Heat Transfer simulations.

Flow Model Set Up

To make the set up of simulation easy Wildkatze provides various command line set up options. Once the basic set up is done then user can add further to the set up by using GUI (in Client - Server mode) or by simply opening the .stree file on text editor of choice.

Steady State

The first is to set up steady state flow model. This is done by

solver.sh -lc flow meshFile -lc pf o.txt

What is happening here?

• flow meshFile generates a journal file o.txt
• -lc tells wildkatze that this is newline or new command starts here. Using multiple -lc can be used to provide multi-line commands as argument to wildkatze.
• -lc pf o.txt part tells wildkatze to process file (pf) o.txt and generate output.stree and run.txt files.
• run.txt is journal file to run simulation using output.stree and meshFile

We set up flow with inlet velocity of 10 m/sec. Note the -vel 10 option added to flow meshFile.

This sets up the steady state flow model.

We can now see that output.stree and run.txt are produced along with some other files.

We now perform 200 iterations and also export the results in Ensight Gold format. Notice -lc export-ensight result

After 200 iterations

We look at velocity contour. There is no steady profile because this problem is more transient in nature.

Unsteady Set Up

To set up as unsteady case

• -dt 1E-3 option here sets up constant timestep simulation
• -vdt 1e-3 sets up case with variable timestep simulation where the time step size is decided by velocity and Courant number setting.
• -pptr options adds transient export of results as Ensight Gold files with default name zDataPP.case

After 200 time steps by solver.sh -lc pf run.txt -lc iterate 200 we get velocity profile

We can see that it produces transient data set as zDataPP.case

We can edit PostProcessExportItem on text editor to change the time export frequency of default 1.0E-3 to 1.0E-2

Turbulence and Forces Export

We can also add the turbulence and force reports from the command prompt.

• -wd options adds Wall Distance model. Do not forget to add Wall distance model with Turbulence
• -kw adds K Omega SST model
• -ke adds K Epsilon model
• -sa adds Spalart Allmaras model

Please check dedicated articles related to Turbulence for full options

We run it for 2000 time steps as

This finishes as

Forces are exported as .csv and .ps formats.

The velocity contour

Turbulent Viscosity

The kinetic energy from K Omega model