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- - **Problems in calculating the fluid traction on the current structure frame in 3D models**
(*http://www.cfd-online.com/Forums/openfoam-solving/58666-problems-calculating-fluid-traction-current-structure-frame-3d-models.html*)

Hi everyone,
I am working oHi everyone,
I am working on an FSI project, the solver is based on the icoFsiFoam but the structure code can deal with geometrically nonlinear structure problems and works in the initial structure frame. the solver is working properly in 2-D and I have tried 2-D axially symmetric cases and the results are satisfactory, but I get problems in running a 3-D model say a complete pipe, I have debuged the solver, and the problem lies in the "setPressure.H" which looks like: //********************************** tensorField gradD = fvc::grad(D); vectorField nc = stressMesh.Sf().boundaryField()[solidPatchID] & inv (I + gradD.T()) * det (I + gradD); vectorField n = nc / mag(nc); symmTensorField solidPatchTraction = sigmaFluid.boundaryField()[fluidPatchID] ; solidPatchTraction *= rhoFluid.value(); tForce.traction() = solidPatchTraction & (n); //****************************************** for a 3-D model, the equation "vectorField n = nc / mag(nc);" can not be calculated correctly and the computation diverges at the beginning: snail@snail-laptop:~/OpenFOAM/snail-1.4.1-dev/run/tutorials/icoStVkFsiFoam$ icoStVkFsiFoam . halfVine /*---------------------------------------------------------------------------*\ | ========= | | | \ / F ield | OpenFOAM: The Open Source CFD Toolbox | | \ / O peration | Version: 1.4.1-dev | | \ / A nd | Web: http://www.openfoam.org | | \/ M anipulation | | \*---------------------------------------------------------------------------*/ Exec : icoStVkFsiFoam . halfVine Date : Aug 06 2008 Time : 16:49:22 Host : snail-laptop PID : 11528 Root : /home/snail/OpenFOAM/snail-1.4.1-dev/run/tutorials/icoStVkFsiFoam Case : halfVine Nprocs : 1 Create time Create dynamic mesh for time = 0 Selecting dynamicFvMesh dynamicMotionSolverFvMesh Selecting motion solver: laplaceFaceDecomposition Selecting motion diffusivity: quadratic Reading transportProperties Reading field p Reading field U Calculating stress field sigmaFluid Reading/calculating face flux field phi Reading mechanical properties Calculating Lame's coefficients mu = 46153.8 Pa lambda = 69230.8 Pa threeK = 300000 Pa Reading field D Calculating field V Calculating stress field gradD Calculating stress field sigma Calculating explicit part of div(sigma) Q Reading coupling properties the relaxation factor is 1 Starting time loop Courant Number mean: 0 max: 0 Time = 1e-07 Setting traction on solid patch Floating point exception (core dumped) from the debug results, the "gradD" and "nc" are calculated correctly but the calculation diverges when trying to calculate "vectorField n = nc / mag(nc)". so far,I haven't figured out why, could anyone give me some ideas? Kind regards feng |

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