Any ideas about how i should model that? I need to model water/air waves travelling upstream in a chanel, i have therefore an inlet and outlet. I need to find a way to specify the waves at the outlet.

Regards,

Nico

There are many ways of specifying the boundary condition.The simplest case will be the characteristic based boundary condition.You can find the details in any CFD book.If you do a literature search for non reflection boundary conditions you can find different ways of implementation of these boundary conditions.

-H