Swirling flow as a boundary condition
 

Hi,

I want to simulate a flow in a pipe. my boundary condition, is velocity at the internal of the pipe. velocity has two componants: a) an unsteady axial flow
b) a steady circumferential flow.

I think it requires a UDF. I have written the UDF for the first part. it is easy.

But I don't know how can I do the second part.
Is there any one can help me ?