[nuimlabib]

I don´t know what can i do to have an accurate coefficient of aerodynamic of airfoil, at a reynolds number of 3*10^6. I try to do several simulations,
with different types of turbulence models, such as spallart-allmaras, k-epsilon,
k-omega and even reynolds stress, but the outcome was not accurate enough, taking into account real wind tunnel data.
I realize that spallart-allmaras model is not the best one, due to it was designed for transonic speeds,
but i think that i using K-W model is best result with modify the turbulence intensity parameter with magnitude less than 0.1%..but i fell that the result still
not acurate enough for cd (drag coefficient). i have done the grid mesh with more number of cell..but still not accurate..
i need some suggestion what my mistake occure and what should i do to get the better result for cd that approach the experimental data..i try simulate the naca 4415 type
please help me..