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-   -   compressible low-Re turbulence model (https://www.cfd-online.com/Forums/openfoam-solving/117903-compressible-low-re-turbulence-model.html)

immortality May 17, 2013 02:05

compressible low-Re turbulence model
 
what low-Re models are available for compressible flows?
I know there isn't any for kOmegaSST,but what are probable replacements(for other models)?

jola May 17, 2013 02:51

Most low-Re models can be used also for compressible flows, assuming they are formulated in a correct way. Only hypesonic flow with very strong compressibility effects require special compressible turbulence models. You can find equation details here: http://www.cfd-online.com/Wiki/Favre...okes_equations

immortality May 17, 2013 09:14

Thank you Mr.Larrson.
I noticed befor that for example there is not any low-Re kOmegaSST model for compressible flows in OF
http://www.openfoam.org/mantisbt/vie..._page.php?id=6
which low-Re model you suggest to me?how can I find the appropriate coefficients,is there an example tutorial?
thanks.

ignacio May 17, 2013 09:51

Hello Ehsan,

chtMultiRegionFoam uses Low Reynolds models for compressible flows.
I am using kOmega SST-LowRe with it now
=)

immortality May 17, 2013 10:51

Hi Ignacio.
thanks for your replying.
where turbulent models are there in the folder of chtMultiRegionFoam?
then why Dr.Weller told me that they have not a sponsor for kOmegaSST low-Re models?
could you guide me more specific to find the model and related coefficients?
thanks.

immortality June 5, 2013 22:55

kkLOmegaSST
 
hi
@Ignatio:
Dear Ignacio
Could you please tell me more how to perform a low-Re turbulent study in a compressible unsteady case?
There are some folders in the solver you mentioned.
And what about other settings and mesh requisits to have a low-Re study?
Could you send me your case please?
@Jola:
Dear Jola could you introduce me some of methods that are appropriate for compressible to be more certained?
is kklOmegaSST suitable(for more sure)?
(Dr.Weller told me its an incompressible method)
How can i find out incompressible models are also applicable for compressible cases from the formulas?
What other methods exist?
Thanks

pete June 6, 2013 03:57

Just make sure that when impementing the turbulence model the incompressibility condition of zero divergence of the velocity field has not been used. In compressible flows this assumption is not correct and you can not use it in for example the Boussinesq eddy viscosity assumption. CFD-Wiki has more info, look for example here:

http://www.cfd-online.com/Wiki/Bouss...ity_assumption

immortality June 10, 2013 09:09

Hi
I'm using low-Re kOmegaSST but time step is too low(about 5e-10) due to small cell near the wall I assume.how can improve it for having more quick run?

immortality June 11, 2013 04:58

2 Attachment(s)
Hi again
since rhoCentralFoam is explicit I changed to sonicFoam.
also now I use LaunderSharmaKE.
now run is rapid enough.but a problem is seen in the first top cell in opening.its pressure goes too high.I think because velocity is near zero in the first cell center(in laminar-sublayer) and since I have set a totalPressure in opening the pressure in the cell near the wall goes high.am I right?!
or its only because of mesh in flow-direction that is much bigger than normal to wall direction?
I'll attach a figure soon/.


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