Hi,

I am doing LES with surface roughness at the wall. I use the universal log law which includes effect of roughness as the wall model:

u/u_tau=log-law - D, where D is function of ln(ks), with ks is roughness size.

But I am not so satisfied with the result. Anybody knows a better way (and references please) to model the surface roughness than this old model by Nikuradse (Schlichting Ch.20) and Cebeci&Chang (1978)?

Thanks

This might not be exactly what you want but it might give you alternatives...

Look at formulation of type E(ks+) = E / (1 + 0.3 * ks+)(matches well experimental data and is cheap to implement)? For an enhanced variation look at Naot (1984) . For more empirical relationships, look at Cebeci and bardshaw (1977; you might have this one) and Sajjadi and Aldrige (1993)...