First - changing two things in a simulation at the same time is obvious not a good approach (mesh AND turbulence model).

Further I need to say, that first you would need to find out, where your simulation comes to a mesh-independente solution (this question can be anbswered with no regard to which turbulence model you are using, if properly implemented in the CFD solver), and only on a mesh level, where the CFD solution is independent from the mesh resolution you can start to make judgements about model errors or about which turbulence model is more suitable for your particular application.

In contrary, if your solution is not yet mesh independent, i.e. the mesh is still too coarse, you are looking on a not known mix of discretization errors and model errors. This can mislead you to a misjudgement about a particular physical model and on the next following refinded mesh the situation (with the two models in question) might be reversed in comparison to what you have observed on the coarser mesh.

This CFD methodology has been outlined almost 22 years ago in the so-called "CFD best practice Guidelines for Industrial CFD".

https://www.ercoftac.org/publications/ercoftac_best_practice_guidelines/

The report can be ordered on this page from ERCOFTAC.

The methodology says, that the following hierachy of CFD error quantification and elimination should be observed:

1) round-off error

2) iteration error (cut-off error with respect of stopping a solution process at a certain iteration number or by matchig a certain quantitative convergence criterion)

3) spatial and time discretization error

...and only afterwards you can investigate model errors of physical models.

Any attempt to investigate more than just one error source at the same time or to change the order of investigation of the errors from this error hierarchy potential will lead to erroneous CFD result.

Best regards,

Dr. Th. Frank.

Thomas Frank Thanks for the answer.The other condition are same for both model. It is necessary to change the mesh if I am changing the turbulence mode to satisfy the other criteria for the model like desired y+ for k-w below 1 and k-e model 30 to 500 . I will follow "CFD best practice Guidelines for Industrial CFD".

E.g. with the Realizable k-eps model and the enhanced wall treatment you run this model on the same mesh like a k-omega based turbulence model.

The SST model is preferred over the baseline k-omega turbulence model so (and much more preferred over any kind of k-epsilon based model anyway).

Regards,

Dr. Th. Frank.