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Originally Posted by sbaffini

Indeed, if y+ =4 is relative to the finest grid, it is confirmed to be a wall function problem. I can't double check now, but I'm pretty sure that the k-omega sst model in CFX uses an all y+ wall function, which means that a wall function is always active. While, in theory, such wall functions should be insensitive to the specific y+ value, they are not perfect and your case is very far from the typical wall function

Originally Posted by cfdnewbie

yes, at least in the viscous sublayer. The size of your grid cell (or the number of points per unit length) determine the smallest scale you can catch on a given grid. From information theory, the Nyquist theorem tells us that we need at least 2 points per wavelength to represent a frequency (we need to be able to detect the sign change). However, 2 points per wavelength is just for Fourier-type approximations.

Originally Posted by vinerm

That's a wrong notion that RANS or EVM models are introduced to get faster results or are expected to be used with coarse mesh. There is no such assumption behind development of these models. The only assumption in EVM is that the turbulence is isotropic and non-EVM RANS, such as, RSM don't even have that assumption.

And when it comes to wall treatment, it is not directly linked with turbulence model; even LES requires wall treatment. is a non-dimensional (Reynolds) number and