In SST k omega model the flow is resolved up to the wall. For this the y+ =1. However, in some cases where the solution is converged and showing fairly good results, the y+ values are different.
Can this be treated as an acceptable solution?
Off course you should check the values. The dimensionless wall distance y+ should be approximately = 1 if you adopt a near wall model approach (mesh refinement) and it can lies between 50 and 500 if you adopt a wall function approach.
Franco
Some factors should be considered which the most significant is the turbulent boundary layer. If you're using any kind of low Reynolds turbulence model considering enhanced wall treatment (as your K-W SST model), so you need to make sure that you stay in the laminar sub layer region where velocity profiles is assumed to be laminar and viscous stress dominates the wall shear which means (Y+
y+ is the near wall grid spacing nondimensionalised using the so called shear stress velocity. It is effectively a Reynolds number. In order to resolve the laminar sub layer you need a value of less than 1. However, you do not have to slavishly apply the rule. Normally I find that an average value over the surface of y+ =1 is adequate. But the best approach is to find out for yourself: run the code twice with two different y+ values and see what happens to the flow field. If it does not change, in any way you care about, then the coarse grid is adequate!
Off course you should check the values. The dimensionless wall distance y+ should be approximately = 1 if you adopt a near wall model approach (mesh refinement) and it can lies between 50 and 500 if you adopt a wall function approach.
Franco
Yes for sure , as Franco mentioned the dimensionless wall Dis should be 1 and refine your mesh to about 500 to get higher data accuracy .
Your simulating ?
Regards
Parag:
All answers above are somewhat correct.
The best answer would depend on how the near wall turbulence model is implemented in the solver/code you are using.
The original two layer zonal model developed by Chen and used in the earlier versions of Fluent and Star-CCM required y+
Parag ji, You should always check your y+ value as your near wall results will greatly depends on y+. It should be 1 for most of the cases, but it may be acceptable as long as your fist grid point lie in the range of viscous sub laye i.e. y+
Depending on the problem and software, it can be set as interval of values.
Which is the source of that image "Politécnico di Milano"? @Franco Concli
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