[nschloe]

Hi all,

with incompressible Navier-Stokes, I'd like to build a PDE for Kármán's vortrex street and I wonder what consistent boundary conditions for the velocity u and the pressure p would be.

While on the obstacle and the tube walls I'd employ no-slip-no-penetetration for u and free boundary conditions for p, i.e.,

u = 0,
n.grad(p) = 0,

(where n is the outer normal), the situation for the inlet and outlet are less clear to me.

To force a inflow on the left, one could certainly use something along the lines of

u = ((y-tube_lower)*(tube_upper-y))
(0.0 )

How about the pressure here, though? What about the outlet?