Surface Roughness Problem
 

Dear All Flow 3D Modellers :),

Now I am creating models of simple open Channel which its length is 200 m with various Surface Roughness. To input Surface roughness, I just used the equation which is mentioned in the users manual "FLOW-3D Documentation, Release 10.1.0" page 409. the input symbol is k which is derived from manning's , Rh (Hydraulic adius) and Dh (Hydraulic Diameter). As my mannings are 0.035 and 0.05 and my channel size is 25.5 m width and 10 m depth, hence it yields k = 0.5886 ( for n = 0.035) and k=2.602 ( for n = 0.05). Then , I have make running for those two value of k ( surface roughness), but unfortunately both results show the same value of water depth ( please see figures on attachment files), according to my knowledge in open channel they should have different water depth result. Could anyone help me to give some comment that I may have made some mistakes in this model?
Thank you so much :)

Best Regards,
Roy

Dear Roy,

Is it possible that something with physics is wrong?

Dear Sehran
 

Dear Sehran,

I think you're correct, it may have mistake with Viscosity and turbulence. Let me check first , then I will let you know.
Thank you so much Sehran .. :)

Cheers

Roy,