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-   -   Differences between simpleFoam an turbFoam (http://www.cfd-online.com/Forums/openfoam-solving/60429-differences-between-simplefoam-turbfoam.html)

 francois September 30, 2005 07:33

I'm wondering if I'm right or

I'm wondering if I'm right or not when I compare the differences between simpleFoam and turbfoam:

* both are for incompressible flow and resolve the Naviers-Stokes equation with RANS closure.

* turbFoam is for unsteady simulation and use the PISO algorithm.

* simpleFoam is for steady simulation and use the simple algorithm.

In the usermanual we can see that simpleFoam is for non-newtonian flow. But is this application still usable for Newtonian flow ?

Furthermore, I have a few question about the use of lowreynolds number RANS model:

* do we have to check the Y+ before running a low or High reynolds RANS model (like in fluent). So, must the mesh be reffined near the wall accordingly:
- Y+>40 for highReynolds RANS models
- y+=1 for lowReynolds RANS models

And for the statistics (like mean velocity and pressure fields):

the simpleFoam application gives the mean fields while for the turbFoam application we have to compute them. In this case are they already computed in turbFoam and if so with which variable can we access them.

Thank's a lot for your answer. I know this question may be stupid but I'm new to OpenFOAM and C++

Regards
Francois

 pierre September 30, 2005 08:30

1. simpleFoam uses the SIMPLE

1. simpleFoam uses the SIMPLE algorithm and can be used fot BOTH newtonian or non-newtonian fluids, you just have to specify the viscosity model in the constant/transportProperties file

2. One can specify which turbulence model to use in constant/turbulentProperties file.
Depending on the model you use, you have indeed to create a mesh adequate for that model, you can check Y+ with the checkYplus utility for example.

3. run the turbFoam tutorial it will answer all the questions about variable available,
but again depending on the flow you compute the converged result can be unsteady or steady, you can use turbFoam to calculate a steady-state calculation, the time step becomes a kind of iteration counter similar to simpleFoam then

J'espere que ca aide

Pierre

 francois September 30, 2005 09:54

I have already run this tutorial but I must admit that it was not in depth.
Good luck for your PhD ... with OpenFOAM it will be funy ...

Francois

 jballen November 15, 2005 15:03

How does one check yplus for c

How does one check yplus for compressible, turbulent cases? For example using k-epsilon.

Thanks
Jeff

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