Menter SST Blending Functions

baobei · May 24, 2016, 13:45

Hello Everyone!

I'm using a cartesian based mesh, where a cube is divided into a defined number of cells together with a RANS solver and Menter's SST turbulence model.

I have a small question, given that many people on this website are more familiar with CFD and hopefully could share their opinion on this next question, it would be much appreciated.

Q. Are the two blending functions used in Menter's SST (any) better to be cell defined or cube defined?

I couldn't really find the answer to it, not even in the CFL3D manual, so any help would be appreciated.

Kind Regards

davidwilcox · May 26, 2016, 07:15

i think the answer you are looking for is in the gauss-divergence theorem. that is to say the spatial gradients of the fluxes on on all sides of the cube, when summed have to equal zero for it to be conservative. in cfd, conservativeness is very important regardless of the functions involved. Note: the blending function is no more than a switching mechanism that becomes the k-omega near the walls and the k-epsilon far from it. That being said, and also pertaining to your original question, you would need to define your "cube height" at the wall well.

May 24, 2016, 13:45	Menter SST Blending Functions	#1
baobei New Member Join Date: Dec 2015 Posts: 1 Rep Power: 0	Hello Everyone! I'm using a cartesian based mesh, where a cube is divided into a defined number of cells together with a RANS solver and Menter's SST turbulence model. I have a small question, given that many people on this website are more familiar with CFD and hopefully could share their opinion on this next question, it would be much appreciated. Q. Are the two blending functions used in Menter's SST (any) better to be cell defined or cube defined? I couldn't really find the answer to it, not even in the CFL3D manual, so any help would be appreciated. Kind Regards

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May 26, 2016, 07:15		#2
davidwilcox Senior Member david Join Date: Oct 2012 Posts: 142 Rep Power: 13	i think the answer you are looking for is in the gauss-divergence theorem. that is to say the spatial gradients of the fluxes on on all sides of the cube, when summed have to equal zero for it to be conservative. in cfd, conservativeness is very important regardless of the functions involved. Note: the blending function is no more than a switching mechanism that becomes the k-omega near the walls and the k-epsilon far from it. That being said, and also pertaining to your original question, you would need to define your "cube height" at the wall well.