Hello I'm quite new in CFD

I'm reading about turbulence models and y+...

What does RNG mean?

I know that the difference between K-epsilon and RNG k-epsilon models are the constants in the transport equations but what is the purpose to change these variables and when we used each model?

Thanks

The RNG k-epsilon turbulence model is supposed to perform better than the standard k-epsilon model in all cases. Not only the constants in the transport equations change, but also there is an addition of a term in the source term of the epsilon equation.

The RNG k-e equations have been tuned based on theory of a turbulent flow (RNG means ReNormalization Group) while the standard k-e is empirically tuned on simple flows (shear, jet, grid turbulence...).

The RNG model then emphasizes the mathematical consistence but it has the same conceptual drawbacks as any k-e model: the results are not so good when there is a sensitive anisotropy of the turublent flow.