# y+ for k-omega = 30 ???

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 May 15, 2006, 05:59 y+ for k-omega = 30 ??? #1 Ralf Schmidt Guest   Posts: n/a Hi, the Fluent Manual suggests to have the y+ for k-w within the log layer 30 < y+ < 300 - a value close to the lower bound is most desirable. I do not know, if thats a good idea. I have bad results compared to the same msh with k-e and wall functions. The other point is, that for y+ = 30, the first cell is ab. 10% of the charactersitic lenght (diamater of a cylinder in axial flow). Any Ideas? Ralf

 May 15, 2006, 11:03 Re: y+ for k-omega = 30 ??? #2 fanzhong Meng Guest   Posts: n/a hi In Fluent user's manual,it is y* should be in the region between 30 to 300. not y+! If you want to use k-w model with enhanced wall treatment, you should alway keep your y+ close to 1. In this way, you can probably solve the boundary layer better! fanzhong Meng

 May 16, 2006, 02:05 Re: y+ for k-omega = 30 ??? #3 Ralf Schmidt Guest   Posts: n/a Hi! Thanks for your reply. But: the Fluent Manual (FLUENT 6.2 Documentation) is very clear at this point: node466, section 11.10.4 "Near-Wall Mesh Guidelines for the k- omega Models ...if [Transitional Flows] option is not active, then the mesh guidelines should be the same as for the wall functions" and further on: node463, section 11.10.1 "Near-Wall Mesh Guidelines for Wall Functions For standard or non-equilibrium wall functions, each wall-adjacent cell's centroid should be located within the log-law layer, 30 < y+ < 300. A y+ value close to the lower bound y+ = 30 is most desirable." Now, the question might be, if it is importand to have the "Transitional Flows option" not active for a cylinder in axial flow at Re = 20000 (based on cylinder Diameter)? Any Idea??? Ralf

 May 20, 2006, 17:28 Re: y+ for k-omega = 30 ??? #4 Donald Guest   Posts: n/a Fluent's k-omega model is not good, look at the formula from standford university. Use rsm instead.

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