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Boundary conditions for Stokes problem

0 votes

Hi,
I have question in demo version: "demo_stokes-taylorhood.py". Why there are used Dirichlet boundary condition for pressure on outflow:
"# Boundary condition for pressure at outflow x0 = 0
zero = Constant(0)
bc2 = DirichletBC(W.sub(1), zero, sub_domains, 2)"
On outflow we have only do-nothing condition.
Could someone explain it.
Thanks in advance

asked Jun 9, 2014 by Gozel FEniCS Novice (140 points)

I believe this is a bug in the demo. The "do-nothing" condition is built in weakly into the form and the Dirichlet condition on pressure is redundant. Try omitting it and you'll see that it has practically no effect on the solution.

commented Jun 9, 2014 by MiroK FEniCS Expert (80,920 points)

thanks a lot.

commented Jun 9, 2014 by Gozel FEniCS Novice (140 points)

@MiroK - If you think it's a bug, could you report it on Bitbucket?

commented Jun 12, 2014 by Garth N. Wells FEniCS Expert (35,930 points)

@Garth N. Wells Done.

commented Jun 12, 2014 by MiroK FEniCS Expert (80,920 points)
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