[k.giannoko]

Dear All,

I simulate a 2d poiseuille flow. I want to impose a wall slip boundary condition at the main direction of flow (z-direction). This slip condition is varying with tube diameter. From a quick search, I found that there are two main ways to implement this. Firstly, if you make your own boundary condition and secondly by using the codedFixedValue command. The pipe is not straight and the radius is different from point to point.
The condition is something like that:

Uz = f(R(z))* dUz/dy , where f() is function of local R and R(z) is radius function of z-direction
Uy = 0
Ux = 0

How can I implement such a boundary condition?

Any help is appreciated ,

K.G