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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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mean curvature in comsol 4.2

Posted Jun 20, 2011, 8:22 a.m. EDT Computational Fluid Dynamics (CFD), Geometry, Mesh Version 4.2 3 Replies

Christian Kelb
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Hi!

For a moving-mesh problem I am trying to get the value of the mean curvature of a surface. 'r', like in Comsol 4.1 doesn't seem to work anymore since it says 'unknown variable'.

Can anyone help me?

Best regards,
Christian
3 Replies Last Post Jul 27, 2012, 7:10 a.m. EDT
Christian Kelb
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Posted: 1 decade ago Jun 20, 2011, 11:30 a.m. EDT
As a suggestion:

Is there a way to compute the gradient of the normal vector of the surface?
I am unable to find anything in the documentation apart from the formulas I already know.

Best regards,
Christian
As a suggestion: Is there a way to compute the gradient of the normal vector of the surface? I am unable to find anything in the documentation apart from the formulas I already know. Best regards, Christian
Christian Kelb
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Posted: 1 decade ago Jun 21, 2011, 10:50 a.m. EDT
Ok, next idea:

I discovered, that there is a differential function d(f,x) where f is the derived function and x the derivation direction. I tried to get the gradient of the normal vector as

grad(n) = d(nx,x) + d(ny,y) + d(nz,z)

but this produces zero for me. Am I using the wrong normal vector?
Ok, next idea: I discovered, that there is a differential function d(f,x) where f is the derived function and x the derivation direction. I tried to get the gradient of the normal vector as grad(n) = d(nx,x) + d(ny,y) + d(nz,z) but this produces zero for me. Am I using the wrong normal vector?
Karl Sundermann
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Posted: 1 decade ago Jul 27, 2012, 7:10 a.m. EDT
Hello,

You have find the answer for your problem? I've the same. It produces 0 for me too.
You tried weak contribution with divergence theorem? For that the is to calculate the [ ] terms. You see what I mean?
Hello, You have find the answer for your problem? I've the same. It produces 0 for me too. You tried weak contribution with divergence theorem? For that the is to calculate the [ ] terms. You see what I mean?

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