# turbulent rectangular U-Pipeflow - Velocityproblem

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 November 25, 2016, 17:29 turbulent rectangular U-Pipeflow - Velocityproblem #1 New Member   Join Date: Nov 2016 Posts: 8 Rep Power: 9 Hey guys, I'm trying to run an as i think quite simple case - still it ain't working. I've got a rectangular U-Pipe with an incompressible, turbulent flow of water. Beside the geometric details i only got the Volume which flows in and with it of course the velocity. I'm using simpleFoam, k-Epsilon-model, RAS. blockMesh works, simpleFoam runs without an error. My Problem is, that the velocity doesn't work well. I've git a fixed "inlet-Velocity" of 0.3339 m/s but when viewing with ParaView, i get a velocity of 0.001 (or something small like this) after the first time step. I made a lot of suggestions about the correct BCs and tried as much as i could by try and error- still i got this problem. Another suggestion of mine was, that the "internal faces", which are "connecting"/between the five blocks of which the U-Pipe consists, are false defined- but as i read: there doesn't have to be any special definition, they're flowing through automatically. When viewing "p" in ParaView, it's possible to see the change through the complete Pipe - this is why i think that ain't the problem. (When modelling a straight pipe, out of one Block, there ain't a Problem [same BCs etc]) So there must be something wrong with my BCs- and as i said, i tried a lot of different BCs and ain't got any more ideas. I hope, that someone else can help me out and has a better idea... I'm posting a version of my case, of which i thought it might have worked. Thanks in advance for any ideas which even might help!!! Code: Code: ``` /*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 4.1 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class volVectorField; object U; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 1 -1 0 0 0 0]; internalField uniform (0 0 0); boundaryField { inlet { type fixedValue; value uniform (0 0 -0.3338675216); } outlet { type zeroGradient; } fixedWalls { type noSlip; } } // ************************************************************************* //``` Code: ``` /*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 4.1 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class volScalarField; object p; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // dimensions [0 2 -2 0 0 0 0]; internalField uniform 0; boundaryField { inlet { type zeroGradient; } outlet { type fixedValue; value uniform 0.2045380588; } fixedWalls { type zeroGradient; } } // ************************************************************************* //``` Code: ``` /*--------------------------------*- C++ -*----------------------------------*\ | ========= | | | \\ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \\ / O peration | Version: 4.1 | | \\ / A nd | Web: www.OpenFOAM.org | | \\/ M anipulation | | \*---------------------------------------------------------------------------*/ FoamFile { version 2.0; format ascii; class dictionary; object blockMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // convertToMeters 0.001; vertices ( (0 0 0) //0 (26 0 0) //1 (26 16 0) //2 (0 16 0) //3 (0 0 -1938) //4 (26 0 -1938) //5 (26 16 -1938) //6 (0 16 -1938) //7 (0 0 -1968) //8 (26 0 -1968) //9 (26 16 -1968) //10 (0 16 -1968) //11 (246 0 -1968) //12 (274 0 -1968) //13 (274 16 -1968) //14 (246 16 -1968) //15 (246 0 -1938) //16 (274 0 -1938) //17 (274 16 -1938) //18 (246 16 -1938) //19 (246 0 0) //20 (274 0 0) //21 (274 16 0) //22 (246 16 0) //23 ); blocks ( hex (4 5 6 7 0 1 2 3) (10 10 20) simpleGrading (1 1 1) hex (8 9 10 11 4 5 6 7) (10 10 20) simpleGrading (1 1 1) hex (9 12 15 10 5 16 19 6) (10 10 20) simpleGrading (1 1 1) hex (12 13 14 15 16 17 18 19) (10 10 20) simpleGrading (1 1 1) hex (16 17 18 19 20 21 22 23) (10 10 20) simpleGrading (1 1 1) ); edges ( ); boundary ( fixedWalls { type wall; faces ( (2 3 7 6) (3 0 4 7) (0 1 5 4) (1 2 6 5) (6 7 11 10) (7 4 8 11) (4 5 9 8) (5 6 19 16) (19 6 10 15) (12 15 10 9) (5 16 12 9) (15 14 18 19) (18 14 13 17) (16 17 13 12) (22 23 19 18) (23 20 16 19) (20 21 17 16) (21 22 18 17) ); } inlet { type patch; faces ( (0 3 2 1) ); } outlet { type patch; faces ( (20 23 22 21) ); } ); mergePatchPairs ( ); // ************************************************************************* //``` Last edited by Bob!; November 26, 2016 at 05:25.

 November 27, 2016, 05:47 #2 New Member   Jeroen Join Date: Oct 2016 Posts: 21 Rep Power: 9 Is your inlet faced towards the -Z direction as your velocity? Could you try and set the pressure to 0 and leave the velocity? Try running it with Turbulence off; Hope you find whats wrong.

 November 28, 2016, 17:17 #3 New Member   Join Date: Nov 2016 Posts: 8 Rep Power: 9 Hey thanks a lot for the reply! The inlet should be fine and - however (because i definitely tried before)- you were right with your pressure assumption! It works and it works well as it seems to me =) Wouldn't have tried it again without your comment - thanks a lot!

 Tags incompressible flow, inlet and outlet, velocity