How to use a variable sand roughness height in wall boundary?? Help me Please.... :(
 

Hi there,

I made some simulations in CFX with the Boundary Condition Wall Non-Slip with a constant value of sand grain roughness. Now, i need to make this value vary with the friction velocity, so I have to introduce the equation in the boundary condition, in order, to get this value in each iteration and actualize the k0 value.

Can anyone tell me how can I do this??

Thanks

P.S: I apologize for my English, but I'm Portuguese! :)