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March 17, 2005, 05:20 |
Hi,
I want to compute a sim
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#1 |
New Member
Max
Join Date: Mar 2009
Posts: 24
Rep Power: 17 |
Hi,
I want to compute a simple jet in still air in order to asses performance of different turbulence models. I have axysimmetric geometry, two coaxial inflows (10 m/s and 1 m/s), external symmetry plane and an ouflow. My problem is very simple: after few iterations pressure equation diverges. I have made the following tests: 1 - switched off turbulence (laminar turbulence model selected) 2 - changed timestep size (turbFoam); 3 - changed viscosity (to stabilize solution); 4 - changed the grid 5 - used version 1.1 but in any case after a variable number of iterations pressure equation diverges, continuity error goes to ~1e30 and so on. I suspect I have made a mistake in grid generation, but I have tryied either with a Gambit grid and blockMesh generated grid. I have attached the blockMeshDict, if you can have a look, I am quite sure I will find the error immediately. Otherwise can you give further test to do to find the problem? Thanks Massimiliano /*---------------------------------------------------------------------------*\ | ========= | | | \ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \ / O peration | Version: 1.0.2 | | \ / A nd | Web: http://www.openfoam.org | | \/ M anipulation | | \*---------------------------------------------------------------------------*/ // FoamX Case Dictionary. FoamFile { version 2.0; format ascii; root "/home/didomax/OpenFOAM/didomax-1.0.2/run/simpleFoam"; case "h3_owngrid"; instance "constant/polyMesh"; local ""; class dictionary; object blockMeshDict; } // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * // arguments "/home/didomax/OpenFOAM/didomax-1.0.2/run/simpleFoam/h3_owngrid"; // convertToMeters convertToMeters 1; // list of coordinates of block vertices vertices ( (0 0 0) (0.7 0 0) (0.7 0.0001 0) (0 0.0001 0) (0 0 0.004) (0.7 0 0.004) (0.7 0.000348623 0.00398478) (0 0.000348623 0.00398478) (0 0 0.140) (0.7 0 0.140) (0.7 0.0122018 0.1394673) (0.0 0.0122018 0.1394673) ); // list of block descriptions blocks ( hex (0 1 2 3 4 5 6 7) (100 1 10) simpleGrading (5 1 1) hex (4 5 6 7 8 9 10 11) (100 1 40) simpleGrading (5 1 5) ); // list of curved edge descriptions edges ( ); // list of patch descriptions patches ( patch jet ( (0 4 7 3) ) patch coflow ( (4 8 11 7) ) patch outflow ( (1 5 6 2) (5 9 10 6) ) symmetryPlane symup ( (8 9 10 11) ) symmetryPlane axis ( (0 1 2 3) ) empty lateral ( (0 1 5 4) (4 5 9 8) (3 2 6 7) (7 6 10 11) ) ); // list of master-slave patch pairs to be merged mergePatchPairs ( ); // ************************************************** *********************** // -- |
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March 17, 2005, 05:32 |
Try running both inlets at the
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#2 |
Senior Member
Eugene de Villiers
Join Date: Mar 2009
Posts: 725
Rep Power: 21 |
Try running both inlets at the same speed. That should tell you whether it is the mesh causing your problem or not.
Otherwise, having a slugflow inlet hitting a wall is generally not a good idea. Similarly, two adjacent jets entering with a large velocity discrepancy and no space between them is not really physical. Remember, you are specifying zeroGradient pressure at the inlet which is patently absurd under such conditions. I suggest you put a profile on the inlet velocities, move the inlets upstream or separate them some distance. |
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