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Calculating the normal Velocity on boundary Patch

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Old   May 23, 2024, 13:33
Smile Calculating the normal Velocity on boundary Patch
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Jonas Rettig
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Hi Guys,
I'm quite confused about the calculation of the normal velocity on the outlet boundary patch.

I have thought about two ways, both give me different results.

1) Calculate the normal Velocity via the Flux Phi (incompressible case) and divide by the face Area (since the flux is defined at the face):

const auto& phip = patch().lookupPatchField<surfaceScalarField>("phi" );

scalarField uNormal= phip/patch().magSf();

2) Calculate the normal velocity via the the velocity of the patch scalar multiplied with the normal patch vector:

const auto& Up = patch().lookupPatchField<volVectorField>("U");


scalarField uNormal2 = (Up & patch().nf());

I know that the Velocity is basically calculated at the cell centers. I thought that lookupPatchField interpolates the velocity to the face, or is this wrong?

I would be happy if someone could help me!

Thanks in advance!

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Old   May 24, 2024, 05:54
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Jonas Rettig
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Is the Question clear?
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Old   May 30, 2024, 09:18
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Domenico Lahaye
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Flux phi has one (single) component of a face.

The velocity vector interpolated to the face has 3 (x y and z) components.
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