Wall function implementation K Omega SSt

cbarry · August 17, 2009, 10:49

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, 10:59

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, 03:21

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, 11:09

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?

August 17, 2009, 10:49	Wall function implementation K Omega SSt	#1
cbarry New Member Christopher Barry Join Date: Aug 2009 Location: Switzerland Posts: 18 Rep Power: 17	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

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
[blockMesh] BlockMesh FOAM warning	gaottino	OpenFOAM Meshing & Mesh Conversion	7	July 19, 2010 15:11
Compilation errors in ThirdPartymallochoard	feng_w	OpenFOAM Installation	1	January 25, 2009 07:59
Problem with rhoSimpleFoam	matteo_gautero	OpenFOAM Running, Solving & CFD	0	February 28, 2008 07:51
Multicomponent fluid	Andrea	CFX	2	October 11, 2004 06:12
Wall function in adverse pressure gradients	stephane baralon	Main CFD Forum	11	September 2, 1999 05:05

August 17, 2009, 10:59		#2
madad2005 Senior Member Anonymous Join Date: Mar 2009 Posts: 110 Rep Power: 17	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.

August 18, 2009, 03:21		#3
cbarry New Member Christopher Barry Join Date: Aug 2009 Location: Switzerland Posts: 18 Rep Power: 17	Thank you Adriano. I'll try implementing some new blended wall functions then. I was hoping I could just modify existing ones.

August 18, 2009, 11:09		#4
cbarry New Member Christopher Barry Join Date: Aug 2009 Location: Switzerland Posts: 18 Rep Power: 17	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]) / (Cmu25kappa_.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?