CFD Online Discussion Forums

CFD Online Discussion Forums (http://www.cfd-online.com/Forums/)
-   OpenFOAM (http://www.cfd-online.com/Forums/openfoam/)
-   -   Wall function implementation K Omega SSt (http://www.cfd-online.com/Forums/openfoam/67501-wall-function-implementation-k-omega-sst.html)

cbarry August 17, 2009 09:49

Wall function implementation K Omega SSt
 
Hi everyone,

I've been having a closer look at the wall function for the kOmegaSST model for incompressible flow in OpenFoam 1.5.

I am new to OpenFOAM though and don't quite understand how the wall function is implemented in OpenFOAM. In literature it is quite commonly written that in the buffer zone, between the viscous sub-layer and the log layer, omega is calculated from a blending function of the form

omega = ('omega viscous'^2 + 'omega log layer'^2)^(1/2)

However, I can't find any such blending function in the OpenFOAM code. Am I just looking in the wrong place? Or does OpenFOAM simply not have spearate functions for the buffer zone?

If OpenFOAM does not use such blending functions, has anyone tried implementing them?

Best regards,

Chris

madad2005 August 17, 2009 09:59

Someone can correct me if I'm wrong, but the SST model in foam has no blended wall functions (infact, I'm not sure if any of the turb models do), although I don't think it is that difficult to add in a simple one like that which you just mentioned. I plan to do it at some point in September, so let me know if you get anywhere with it.

cbarry August 18, 2009 02:21

Thank you Adriano. I'll try implementing some new blended wall functions then. I was hoping I could just modify existing ones.

cbarry August 18, 2009 10:09

I've had another look at the wall function files in OpenFOAM.

It looks like OpenFOAM uses the wall function

omega_[faceCelli] +=
sqrt (k_[faceCelli])
/ (Cmu25*kappa_.value()*y_[faceCelli])

regardless of what sublayer of the turbulent boundary layer it is in.

There must however be an upper bound y+ value upto which the wall function applies. Does anyone know where in the code this upper bound is?


All times are GMT -4. The time now is 09:18.