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vectorField Uwall(Up.patchInternalField() - Up)

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Old   January 25, 2013, 13:23
Default vectorField Uwall(Up.patchInternalField() - Up)
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Dear Foamers,

I am trying to understand the calculation of the dynamic contact angle in dynamicAlphaContactAngleFvPatchScalarField.C and I am having trouble to understand the line:

vectorField Uwall(Up.patchInternalField() - Up);

I know Up is U_.boundaryField()[patchi], but why subtract the velocities on patchi from their values next to patchi ("Up.patchInternalField()")?

Thanks,

Arnout
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Old   January 25, 2013, 17:48
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It seems to me that Uwall is the relative velocity with respect to the wall.
I expect that Up = 0 for fixed walls and nonzero for moving walls.

You can easily verify this by adding
Info << Up << endl;
to the code

Cheers,

L
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Old   January 27, 2013, 18:15
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I had not thought of the possibility of moving walls. Now it makes sense. Thanks for your reply!
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Old   July 10, 2014, 08:42
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Boeleman !!

I am also trying to understand the dynamic contact angle model implemented in the openfoam. I want to know whether "patch().nf()" refers to face unit normals or something else? Also, whats the difference between nf and nhat ?

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Vignesh
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Old   July 17, 2014, 15:36
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nf(), does indeed refer to the face unit normal, so Uwall -= (nf & Uwall)*nf;calculates the velocity parallel to the wall, by subtracting the normal component from the complete velocity vector. nhat() is the normal to the interface of the two phases.
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Old   August 15, 2014, 15:11
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Hey,
I am really not getting the physical meaning of the term vectorField Uwall(Up.patchInternalField() - Up);

Uwall seems to be of type vectorField, but what does the term in brackets mean ?

Thanks in advance!
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Old   August 15, 2014, 18:02
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Quote:
Originally Posted by Anjishnu Choudhury View Post
Hey,
I am really not getting the physical meaning of the term vectorField Uwall(Up.patchInternalField() - Up);

Uwall seems to be of type vectorField, but what does the term in brackets mean ?

Thanks in advance!
Up contains the values of U in the boundary and Up.patchInternalField is the values of U in the cells next to the boundary. Their difference gives the relative velocity !!

Hope this helps
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