# cyclic boundary condition doesn't work in a tube ??

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 April 15, 2010, 08:51 cyclic boundary condition doesn't work in a tube ?? #1 Senior Member   Cyprien Join Date: Feb 2010 Location: Stanford University Posts: 229 Rep Power: 9 Hi ! I try to simulate a flow through a tube (2D) with cyclic boundary condition at the inlet and the outlet. A poiseuille's flow profile (parabolic) is expected along the tube. However, it works only after a distance from the inlet. I belevied that with the cyclic condition, I will get the same profile all along the tube. Why does my simulation is like that ?? I obtain exactly the same profile when I define my inlet and outlet as "patch". My initial conditions are : p : inlet { type zeroGradient; } outlet { type fixedValue; value uniform 0; U : outlet { type zeroGradient; } inlet { type fixedValue; value uniform (4 0 0); } thank you for your help, Cyp

 April 15, 2010, 08:55 #2 Member   David Join Date: Dec 2009 Location: Spain Posts: 58 Rep Power: 7 Can you put here the cyclic condition you have used? David

 April 15, 2010, 09:05 #3 Senior Member   Cyprien Join Date: Feb 2010 Location: Stanford University Posts: 229 Rep Power: 9 In my blockMeshDict I defined : patches ( cyclic inlet ( (0 4 7 3) ) cyclic outlet ( (1 5 6 2) ) wall fixedWalls ( (3 7 6 2) (1 5 4 0) ) empty frontAndBack ( (0 3 2 1) (4 5 6 7) ) ); It is the question you asked me ?

 April 15, 2010, 11:00 #4 Senior Member   Cyprien Join Date: Feb 2010 Location: Stanford University Posts: 229 Rep Power: 9 Indeed, I haven't well defined my cyclic condition. It works now when I defined inout instead of inlet and outlet patches. cyclic inout ( (0 4 7 3) (1 5 6 2) ) For my pressure initial condition, I used inout { type fan; patchType cyclic; f List 1(-5.00); // p_OF = p_real / rho value uniform 0; } Is it the single manner to do ?

 April 15, 2010, 12:11 #5 Member   David Join Date: Dec 2009 Location: Spain Posts: 58 Rep Power: 7 Yes it is the correct manner. You can also use de b.c directMapped, which takes the outlet velocity and recicles it to the inlet patch. David

 April 15, 2010, 14:11 #6 Senior Member   Cyprien Join Date: Feb 2010 Location: Stanford University Posts: 229 Rep Power: 9 I improved my case considering two-phase flow. I use the interFoam solver. I patch well my region. When I launch the interFoam solver, I get this error message : Code: ```Unable to set reference cell for field p Please supply either pRefCell or pRefPoint file: /home/cyp/OpenFOAM/cyp-1.6/run/test07/system/fvSolution::PISO from line 55 to line 60. From function void Foam::setRefCell ( const volScalarField&, const dictionary&, label& scalar&, bool ) in file cfdTools/general/findRefCell/findRefCell.C at line 112. FOAM exiting``` Do you know what does it mean and what's wrong in my case ??

 April 16, 2010, 15:21 #7 Member   David Join Date: Dec 2009 Location: Spain Posts: 58 Rep Power: 7 I don't know what is the problem. When you tried the cyclic condition and it worked, was whit this solver? If not, perhaps this solver doesn't work with the cyclic condition and this b.c for pressure. But I'm just guessing. I suppose you want to fix the mass flux? if not, you can set only: inout { type cyclic; value uniform 0; } for pressure. And fix the velocity in the "boundary field" (0/U). If it still doesn't work...I don't know. But may be the directMapped condition is a good alternative. Sorry for my poor help David mohammad81 likes this.

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