# inflow/outflow Boundary Conditions for flow in pipe

I have a question about boundary condition of solving Navier-Stokes equation through pipe. When I simulate the flow in pipe using periodic boundary condition, it works good. But when I tried to change boundary condition into inflow/outflow condition, then after few iteration, it started to blow up. I'm using a levelset method for interface capturing and general projection method for solving Navier-Stokes equations. I just imposed inflow/outflow boundary condition for velocity and levelset as simple linear extrapolation of inside one. Is there anyway to treat inflow/outflow boundary condition? $\triangle$

• for a meaningful response form this site, you'll want to formulate your issue as a mathematical problem, rather than "if I do this my program crashes" – Carlo Beenakker Mar 22 '15 at 13:39
• Thank for comment Carlo. I'll fix this with mathematical formulation. – CFD_Killer Mar 23 '15 at 19:03