[behzzad93]

hi everyone

i have a serious problem in fluent
what is the udf for permeate flux?...i have to modeling a tube that have an inlet and outlet, but the walls of tube have permeability. indeed i want to model a membrane that fluid enters the inlet and a little bit of fluid passes through the wall(i know the equation for permeability) and rejected fluid is exited from the outlet. so can anyone tell me how can i define a udf for this equation please?..i realized i have to use sink & source method for wall boundary condition, also i have to use "define_source" macro. but i didn't see examples for this section.
i don't know how to write udf for this boundary!!.

thank you