# simulate cross section of 3D fully Devolped poiseuille rectangular closed channel

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 July 2, 2012, 17:57 simulate cross section of 3D fully Devolped poiseuille rectangular closed channel #1 Member   Amin Shariat KHah Join Date: Apr 2011 Location: Shiraz Posts: 86 Rep Power: 6 Hi Dear FOAMers I want to simulate one cross section (2D) of a 3D rectangular closed channel in fully developed poiseuille flow. I know should use cyclic BC but I have no idea to use it. Anybody can upload me a case for study and learning ?

 July 2, 2012, 18:11 #2 Member   Amin Shariat KHah Join Date: Apr 2011 Location: Shiraz Posts: 86 Rep Power: 6 I don't know if cyclic BC is useable for poiseuille flow? How should I implement pressure gradient? Pressure is not cyclic in this flow!

 July 3, 2012, 03:28 #3 Member   Amin Shariat KHah Join Date: Apr 2011 Location: Shiraz Posts: 86 Rep Power: 6 NoBody has done some case like this?

 July 3, 2012, 04:20 #4 Member   Masashi Ohbuchi Join Date: Oct 2009 Posts: 72 Rep Power: 7 Hi, Amin. Please check "channelFoam" source code and "channel395" tutorial. The channelFoam can handle pressure gradient and cyclic boundary in streamwise direction. If you want to simulate duct flow, the boundary condition for span direction should be changed to non-slip wall from cyclic boundary.

 July 3, 2012, 07:16 #5 Member   Amin Shariat KHah Join Date: Apr 2011 Location: Shiraz Posts: 86 Rep Power: 6 Hello Dear Masashi Tanx for your quick answer What should I do with pressure BC? Thank you very much... Last edited by amin144; July 3, 2012 at 09:20.

 July 3, 2012, 20:38 #6 Member   Masashi Ohbuchi Join Date: Oct 2009 Posts: 72 Rep Power: 7 Hi, Amin, Pressure gradient is coded in solver source code as follows. channelFoam.C 00063 fvVectorMatrix UEqn 00064 ( 00065 fvm::ddt(U) 00066 + fvm::div(phi, U) 00067 + sgsModel->divDevBeff(U) 00068 == 00069 flowDirection*gradP <-- here 00070 ); 00071 00072 if (momentumPredictor) 00073 { 00074 solve(UEqn == -fvc::grad(p)); 00075 } So the pressure boundary condition at inlet-outlet should be cyclic.

 July 4, 2012, 03:54 #7 Member   Amin Shariat KHah Join Date: Apr 2011 Location: Shiraz Posts: 86 Rep Power: 6 Hi Dear Masashi Tanx for your answer It seems this way doesn't work for another solver? am I right? So what should I do if I want simulate one cross secttion normal to basis axis of a fully developed rectangular duct with 2d mesh? (my flow is pressure driven) Best wishes for you

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