atmospheric roughness height

Alain BASTIDE

Hi,

I work with atmospheric boundary layer.

wind profile of inlet boundary layer is : u=u_tau/kappa*ln(z/z_0) where roughness height z_0=0.07 meter (flat plane)

Turbulence intensity profile : I_t=1/ln(z/z_0)

I use a law of wall : u_plus=1/kappa*ln(z+/z+_0)

In StarCD Methodology page 6-6, i found that y_p (height of the center of cell) should be 4 times larger than the roughness height.

My questions :

1. I'm looking for publications on roughness height and CFD (witch grid can i take), could you help me?

2. Witch y+ range can i give?

3. Is this modelisation good?

4. Witch lenght scale can i take (i just know that L_30m=100m)?

PS : I try a "power law" for the wind profil and i obtain bad results because i use low wind and power low is for strong wind

Thanks