Bottom shear stress formula

Question

Hi Chris,

It seems that the bottom shear stress is calculated by the form -CdU|U|. I am wondering that this form should be -CdU(U^2+V^2)^(1/2).

Another option for Cd might be Cd=g*n^2/depth^(1/3)

Here, n is the manning roughness and can be calculated by n=ks^(1/6)/(7.66*g^(1/2), which is the formular by Manning-Strickler. ks is the roughness height =1~3*ds (diameter of the sediment)

The bottom shear is important for a river system.

How do you think?

Cheers,

Hiroshi 

Answer 1

Hi Hiroshi,

I've updated the bottom shear stress  -CdU(U^2+V^2)^(1/2) in the latest download.

I'm also thinking of putting in a height scale for this parametrisation. ie average the velocity over the bottom 1m (nominally) to remove the grid-scale dependance

Chris

Comments

Hi Hiroshi, I've added the ability to average the velocity used for bottom stress calculations into the latest download.  The optional keyword in run_aem3d.dat is btm_stress_avg_height (units is m).  If no value is given the bottom value in each column is used.