Hello,

I'm having some trouble with adapting the wall roughness in my turbulence model. Actually, i have two problems. The first problem concerns the overall roughness of all walls that should be increased. If I select the 'roughness' parameter under >>model boundary conditions >> wall boundaries, the roughness parameter is not set in the command file. Even typing the roughness manually in the command file doesn't seem to work, because the solver ignores this value. I'm using the k-epsilon turbulence model. Can anybody tell me what I have to do to change the overall roughness of the walls?

The second problem is that I have to increase the roughness of 1 patch, and leave the roughnesses of the other walls as default. To do this, I will have to program this in Fortran, but can anybody tell me how to program this?

Kind regards Bart

Check USRWRT; there's definitely a model of Wall Function and roughness value available under this section in the manual.

By default, one has a smooth wall function in CFX-4. Therefore check the manual and then implement the function of your linking; although that that is available is a good approximation fairly close to waht can be found in the literature and in more complex form. Naot used a formulation closed to that of CFX, but I cannot remember the date of its publication on the topic.