I am working with jet impingement heat transfer. I am using RSM with non-equilibrium wall functions. i kept the y* above 20 all along.The results are ok .My doubt is whether wall-funtion approach is correct while studying heat transfer.. Will Switching to a two-layer zonal model which uses a one-equation model of Wolfstein be correct physically. Any help is welcome.

(1). You are right to point out that these are "models". (2). So, for the results to be correct, the models must be calibrated and validated for a particular problem at hand. (3). If a model is "physically correct", then it is not a "model". In other words, a model is not the real thing.

I have had more success in "coming close" to matching experimental htc data when using a two-layer turbulence model.

The downside is that this means more grid.

Ron