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Laminar flow problem does not converge for most boundary conditions

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HI,

I have set up a 3D laminar flow problem in a rectangular geometry with an inlet and outlet. The problem presents in reality a fluid exchange problem: a box of fluid is connected to a pump, which introduces another species of fluid from the inlet while the fluid in the box is expelled through the outlet.

I tried a variety of boundary conditions for the inlet and outlet but only few of them result in a converging simulation. Ideally, I would like both inlet and outlet to have laminar inflow/outflow=1e-6 m^3/s; however, this condition does not give a converged solution. I know from your forum that specifying both inlet and outlet boundaries to be velocity/flow rate may cause problems to convergence, so I also tried specifying velocity/inflow at the inlet and a constant pressure at the outlet. However, this works only if pressure=0Pa, which is far from ideal for my system.

Can someone suggest any reason that possibly causes the convergence problem, and what would be the solutions?

Thanks.



0 Replies Last Post Dec 11, 2017, 1:51 p.m. EST
COMSOL Moderator

Hello Nicole Luk

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