non-linear eddy viscosity models

George

Hello, I have read that the non-linear EVM perform much better than the standard k-epsilon and the RNG k-epsilon. Is is true? I have written a CFD code for simulating the flow in an internal combustion engine. I am using the RNG k-epsilon turbulence model and I am thinking for the improvement of my results to incorporate a quadratic or a cubic non-linear EVM. I have found that the most "popular" quadratic model is that of Speziale and cubic model of Craft. Is there any point of using these, or is it a waste of time? I am not willing to use LES or RSM or any other more complex turbulence model.

Thank you in advance.