[Hillie]

Dear Foamers,

I am trying to add the viscous stress term to sonicFoam. Some people on this forum claimed that this has already been done. I have not been able to find it and therefore thought I would start a new thread.

The term that needs to be added to the energy equation is div(tau,U). I have read on this forum that the stress tensor tau should be directly available in the form of 'DevRhoReff'.


if I try to add the following term to the energy equation

fvc::div(DevRhoReff,U)

I get the following error: error:

DevRhoReff was not declared in this scope

Which I guess means that the variable is not defined. I am using kOmegaSST and in the source code I cannot find anything regarding the definition of the stress tensor.

If I work the stress term out for the energy equation I come to the following:

-fvc::div((turbulence->muEff()*(fvc::grad(U)) + turbulence->muEff()*dev2(fvc::grad(U)().T()))& U)

I am wondering if other people got the same term? sorry if this is a bit of a noob question, but this is the first time I am adding some code to OpenFoam and I just want to check if I am not making any noobis mistakes.

[hk318i]

Hello,

This variable, DevRhoRef, isn't available in the solver scope but you can get it from the turbulence object as follows;

turbulence->divDevRhoReff()

Generally, that's how to access any member function within the turbulence library. You have to check if this term is what you are looking for or not.
For more details about the governing equations in OF, please check this post http://www.cfd-online.com/Forums/ope...tml#post555624. Also, you can check the source code here [LINK].

Bw,
Hassan

[Hillie]

Hi Hassan,
Thanks for your reply. My case is compressible. Looking at the compressible turbulence models the stress tensor is not available. (Or i am missing it). I guess the only option is to write the terms out and put that in. Cheers, Hilbert

[hk318i]

I think it is available for compressible flow because this function is defined as virtual function in the base class, check here [LINK].

[Hillie]

Good point, thanks.
after a bit of playing with it I think I got it. The term I came up with is:

fvc::div(turbulence->devRhoReff()&U)

I haven't tested the code yet though.