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

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Old   January 14, 2008, 16:28
Default Hello, Can anyone tell me h
Quinn Tian
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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
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Old   January 18, 2008, 06:29
Default p.boundaryField().snGrad();
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Eugene de Villiers
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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;
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Old   November 17, 2008, 08:11
Default Hi all, I tried this code a
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Kerstin Heinen
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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/"
#1 Foam::sigSegv::sigSegvHandler(int) in "/data/home/openfoam/OpenFOAM/OpenFOAM-1.5/lib/linux64GccDPOpt/"
#2 ?? in "/lib64/tls/"
#3 Foam::tmp<foam::field<foam::innerproduct<foam::vec tor<double>, Foam::Vector<double> >::type> > Foam::operator&<foam::vector<double>, Foam::Vector<double> >(Foam::
UList<foam::vector<double> > const&, Foam::UList<foam::vector<double> > const&) in "/data/home/openfoam/OpenFOAM/OpenFOAM-1.5/applications/bin/linux64GccDPOpt/lami nar

It looks like having problems with the vector product in the last line?

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Old   April 4, 2014, 05:05
Default any quick post processing tool to compute pressure gradients in the domain
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Sabrinho Gonzalez
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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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