I have a question regarding the wind profile computed by TurbSim based on z0 and RICH_NO in a stable atmosphere. It seems to me that TurbSim uses a constant psi in the wind profile calculation, based on a constant z/L calculated from the RICH_NO input. Did I understand correctly? If so, can you explain to me why the psi should be a constant?
I don’t understand why psi should not be a function of height, (z/L from RICH_NO → L from z=HH → psi from Ht/L and z_ref/L):
U=U_Ref*( LOG( Ht / Z0 ) - psiM(Ht) )/( LOG( z_Ref / Z0 ) - psiM(z_ref) )
Example of the difference:
When I calculate the profile with a constant psi of -1.516 (Ri=0.1205 z/L=0.303), I obtain the same profile as TurbSim, ranging from 15.7 m/s at 8.75 m to 18.3 m/s at 229.25 m. When I calculate a varying psi of 0.112 (8.75 m) to 2.921 (229.25 m) (Ri=0.1205 & HH=119m → L=393), I rather obtain a profile ranging from 14.9 m/s (8.75 m) to 19.8 m/s (229.25m). The profiles are obtained with a reference height of 80 m and a reference wind speed of 17.4 m/s.