# How can I get the pressure gradient along the direction normal to the local wall surface

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 January 14, 2008, 16:28 Hello, Can anyone tell me h #1 Member   Quinn Tian Join Date: Mar 2009 Posts: 62 Rep Power: 10 Hello, Can anyone tell me how to the pressure gradient normal to the local wall surface? I have caculated pressure gradient at the first node away from surface. However, I don't know how to get the information of local normal vectors to the wall. Thanks

 January 18, 2008, 06:29 p.boundaryField().snGrad(); #2 Senior Member   Eugene de Villiers Join Date: Mar 2009 Posts: 725 Rep Power: 14 p.boundaryField()[patchID].snGrad(); Which is generally zero for walls. You seem to want to extrapolate the pressure gradient. To do this you will need: volVectorField gradp = fvc::grad(p); vectorField nearSurfaceGradP = gradp.boundaryField()[patchID].patchInternalField(); const vectorField& surfaceNormal = mesh.boundary()[patchID].nf(); scalarField gradpWallNormal = nearSurfaceGradP & surfaceNormal;

 November 17, 2008, 08:11 Hi all, I tried this code a #3 New Member   Kerstin Heinen Join Date: Mar 2009 Location: Ludwigshafen, Germany Posts: 27 Rep Power: 10 Hi all, I tried this code above to calculate the gradient of a tensor component in normal direction to the wall... label wallPatchID = mesh.boundaryMesh().findPatchID("wall"); volScalarField S11 = StressTensor.component(tensor::XX); volVectorField gradS11 = fvc::grad(S11); vectorField nearSurfaceGradS11 = gradS11.boundaryField()[wallPatchID].patchInternalField(); scalarField gradS11WallNormal = nearSurfaceGradS11 & surfaceNormal; Compiles without errors. But I get an error message if I try to run the case. #0 Foam::error::printStack(Foam:stream&) in "/data/home/openfoam/OpenFOAM/OpenFOAM-1.5/lib/linux64GccDPOpt/libOpenFOAM.so" #1 Foam::sigSegv::sigSegvHandler(int) in "/data/home/openfoam/OpenFOAM/OpenFOAM-1.5/lib/linux64GccDPOpt/libOpenFOAM.so" #2 ?? in "/lib64/tls/libc.so.6" #3 Foam::tmp, Foam::Vector >::type> > Foam::operator&, Foam::Vector >(Foam:: UList > const&, Foam::UList > const&) in "/data/home/openfoam/OpenFOAM/OpenFOAM-1.5/applications/bin/linux64GccDPOpt/lami nar PTT" It looks like having problems with the vector product in the last line? Kerstin

 April 4, 2014, 05:05 any quick post processing tool to compute pressure gradients in the domain #4 New Member   Sabrinho Gonzalez Join Date: Nov 2009 Posts: 5 Rep Power: 9 Hi, Do we have any option/tool in openfoam like a post processing tool to compute pressure gradients in three directions in a 3D domain? Thanks, regards

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