# High local velocities in interDyMFoam

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 May 23, 2013, 04:48 High local velocities in interDyMFoam #1 Member   Anon Join Date: Oct 2012 Posts: 33 Rep Power: 6 Hi, I have a simulation where a high speed jet of water (38.38 ms-1) interacts with a rotating turbine bucket in interDyMFoam. I have a problem with the courant number being very low (10-8), much because of an extremely high velocity (10⁵ ms-1) in a few cells around the bucket. I wonder if anyone else has seen this behavior in interDyMFoam, and maybe knows how I can avoid velocities of this magnitude? Kind regards, Jone

 June 28, 2013, 22:38 #2 New Member   Join Date: Apr 2013 Posts: 1 Rep Power: 0 hi Jone Maybe you can define another parameter in creatFields.H to replace Alpha1 for refinement. Like this Add following lines in creatFields.H Info<< "Creating field Laplacian U\n" << endl; volScalarField laplaceU ( IOobject ( "laplaceU", runTime.timeName(), mesh, IOobject::NO_READ, IOobject::AUTO_WRITE ), (mag(fvc::laplacian(U.component(0))) + mag(fvc::laplacian(U.component(1))) + mag(fvc::laplacian(U.component(2)))) ); add following lines in interDyMFoam.C after pressure possion equation loop // --- calculate laplacianU for refinement laplaceU = (mag(fvc::laplacian(U.component(0))) + mag(fvc::laplacian(U.component(1))) + mag(fvc::laplacian(U.component(2)))); // --- calculate average laplacianU dimensionedScalar laplaceUAver = sum(laplaceU * mesh.V()) / sum(mesh.V()); // --- laplacianU laplaceU = laplaceU / laplaceUAver; Logicallly, the field laplaceU will be high on the interface and area with sharp velocity gradient. Don't forget modify costant/dynamicMeshDict, like change: field alpha1; lowerRefineLevel 0.001; upperRefineLevel 0.999; to: field laplaceU; lowerRefineLevel 4; //test upperRefineLevel 1e10; But i am not sure whether the change will be accepted by interDyMFoam, because adaptive mesh refinement code is difficult for me. Hope you succeed!

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