Re: [firedrake] Pressure outlet boundary condition in plane poiseuille flow
What kind of finite element spaces are you using? all the best --cjc On 22 April 2016 at 12:51, Fryderyk Wilczynski <scfw@leeds.ac.uk> wrote:
Hi all,
I trying to test 2d incompressible navier-stokes code, using plane poiseuille flow test case .
I am solving steady state system on a square domain. No-slip on top and bottom walls. Velocity inlet on the left where I specify Dirichlet parabolic profile ("x[1]*(1-x[1])", "0.0"). On the right boundary I specify zero constant pressure.
noslip = Constant((0, 0)) inlet = Function(P2).interpolate(Expression(("x[1]*(1-x[1])", "0.0"))) bc0 = DirichletBC(W.sub(0), inlet, 1) bc1 = DirichletBC(W.sub(1), 0, 2) # zero pressure outlet bc2 = DirichletBC(W.sub(0), noslip, 3) bc3 = DirichletBC(W.sub(0), noslip, 4)
I expect the exact to be v = ( y (1 - y), 0) - (unidirectional flow).
However, I think I must have set that outlet condition up incorrectly as I get vertical flow near the outlet. Is this a common issue? or a sign that there's some bug in my formulation?
Thanks,
Fryderyk
-- http://www.imperial.ac.uk/people/colin.cotter www.cambridge.org/9781107663916
I am using P2 for velocity and P1 for pressure, where P1 = FunctionSpace(mesh, "Lagrange", 1) P2 = VectorFunctionSpace(mesh, "Lagrange", 2) thanks ________________________________ From: firedrake-bounces@imperial.ac.uk <firedrake-bounces@imperial.ac.uk> on behalf of Colin Cotter <colin.cotter@imperial.ac.uk> Sent: 22 April 2016 14:31 To: firedrake Subject: Re: [firedrake] Pressure outlet boundary condition in plane poiseuille flow What kind of finite element spaces are you using? all the best --cjc On 22 April 2016 at 12:51, Fryderyk Wilczynski <scfw@leeds.ac.uk<mailto:scfw@leeds.ac.uk>> wrote: Hi all, I trying to test 2d incompressible navier-stokes code, using plane poiseuille flow test case . I am solving steady state system on a square domain. No-slip on top and bottom walls. Velocity inlet on the left where I specify Dirichlet parabolic profile ("x[1]*(1-x[1])", "0.0"). On the right boundary I specify zero constant pressure. noslip = Constant((0, 0)) inlet = Function(P2).interpolate(Expression(("x[1]*(1-x[1])", "0.0"))) bc0 = DirichletBC(W.sub(0), inlet, 1) bc1 = DirichletBC(W.sub(1), 0, 2) # zero pressure outlet bc2 = DirichletBC(W.sub(0), noslip, 3) bc3 = DirichletBC(W.sub(0), noslip, 4) I expect the exact to be v = ( y (1 - y), 0) - (unidirectional flow). However, I think I must have set that outlet condition up incorrectly as I get vertical flow near the outlet. Is this a common issue? or a sign that there's some bug in my formulation? Thanks, Fryderyk -- http://www.imperial.ac.uk/people/colin.cotter www.cambridge.org/9781107663916<http://www.cambridge.org/9781107663916> [http://assets.cambridge.org/97811076/63916/cover/9781107663916.jpg]
I think I found something wrong in my code, but I don't know how to fix it... It's to do with the way I implement the symmetric velocity gradient term, D = grad(v)+ grad(v)^T , please see attached pdf for description. Also the full code can be found on https://bitbucket.org/fryderyk216/navierstokes/ Thanks ________________________________ From: firedrake-bounces@imperial.ac.uk <firedrake-bounces@imperial.ac.uk> on behalf of Fryderyk Wilczynski <scfw@leeds.ac.uk> Sent: 22 April 2016 14:58 To: firedrake Subject: Re: [firedrake] Pressure outlet boundary condition in plane poiseuille flow I am using P2 for velocity and P1 for pressure, where P1 = FunctionSpace(mesh, "Lagrange", 1) P2 = VectorFunctionSpace(mesh, "Lagrange", 2) thanks ________________________________ From: firedrake-bounces@imperial.ac.uk <firedrake-bounces@imperial.ac.uk> on behalf of Colin Cotter <colin.cotter@imperial.ac.uk> Sent: 22 April 2016 14:31 To: firedrake Subject: Re: [firedrake] Pressure outlet boundary condition in plane poiseuille flow What kind of finite element spaces are you using? all the best --cjc On 22 April 2016 at 12:51, Fryderyk Wilczynski <scfw@leeds.ac.uk<mailto:scfw@leeds.ac.uk>> wrote: Hi all, I trying to test 2d incompressible navier-stokes code, using plane poiseuille flow test case . I am solving steady state system on a square domain. No-slip on top and bottom walls. Velocity inlet on the left where I specify Dirichlet parabolic profile ("x[1]*(1-x[1])", "0.0"). On the right boundary I specify zero constant pressure. noslip = Constant((0, 0)) inlet = Function(P2).interpolate(Expression(("x[1]*(1-x[1])", "0.0"))) bc0 = DirichletBC(W.sub(0), inlet, 1) bc1 = DirichletBC(W.sub(1), 0, 2) # zero pressure outlet bc2 = DirichletBC(W.sub(0), noslip, 3) bc3 = DirichletBC(W.sub(0), noslip, 4) I expect the exact to be v = ( y (1 - y), 0) - (unidirectional flow). However, I think I must have set that outlet condition up incorrectly as I get vertical flow near the outlet. Is this a common issue? or a sign that there's some bug in my formulation? Thanks, Fryderyk -- http://www.imperial.ac.uk/people/colin.cotter www.cambridge.org/9781107663916<http://www.cambridge.org/9781107663916> [http://assets.cambridge.org/97811076/63916/cover/9781107663916.jpg]
participants (2)
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Colin Cotter
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Fryderyk Wilczynski