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Local derivatives on an edge
Posted Jan 14, 2013, 7:29 a.m. EST Parameters, Variables, & Functions Version 4.3a 2 Replies
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Hello Community,
I'm building a 3D model in which edges are randomly oriented. On these edges I'm trying to implement a weak formulation of a pde but I can't figure out how to compute the derivatives in the local coordinate system.
I tried to have a look at the beam physics model and there a derivative orthogonal to the edge is computed by the following expression: "mod1.umod1.vmod1.wts". But even with this information I wasn't able to get the derivatives. I'm really desperate to get the answer because I have been working on this problem for a long time now.
Thanks for your help.
kind regards
Jan Kaul
I'm building a 3D model in which edges are randomly oriented. On these edges I'm trying to implement a weak formulation of a pde but I can't figure out how to compute the derivatives in the local coordinate system.
I tried to have a look at the beam physics model and there a derivative orthogonal to the edge is computed by the following expression: "mod1.umod1.vmod1.wts". But even with this information I wasn't able to get the derivatives. I'm really desperate to get the answer because I have been working on this problem for a long time now.
Thanks for your help.
kind regards
Jan Kaul
2 Replies Last Post Jan 15, 2013, 1:31 p.m. EST
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Posted:
1 decade ago
Jan,
For field dependent variable u, the tangential derivative along the edge in the x-direction can be calculated as uTx.
For example, gradient along the edge of the field variable u is
grad(u)={uTx, uTy, uTz}
If you are using weak contribution, then gradient of the test function is:
grad(test(u))={test(uTx), test(uTy), test(uTz)}
Also, you can use dtang() operator to compute derivatives in the tangential direction:
grad(u)={dtang(u,x), dtang(u,y), dtang(u,z)}
Regards,
Sergei
For field dependent variable u, the tangential derivative along the edge in the x-direction can be calculated as uTx.
For example, gradient along the edge of the field variable u is
grad(u)={uTx, uTy, uTz}
If you are using weak contribution, then gradient of the test function is:
grad(test(u))={test(uTx), test(uTy), test(uTz)}
Also, you can use dtang() operator to compute derivatives in the tangential direction:
grad(u)={dtang(u,x), dtang(u,y), dtang(u,z)}
Regards,
Sergei
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Posted:
1 decade ago
Thank you for your reply.
The dtang Operator should solve my problem but in my 3D model comsol doesn't seem to be able to evaluate dtang on an edge.
regards
Jan Kaul
The dtang Operator should solve my problem but in my 3D model comsol doesn't seem to be able to evaluate dtang on an edge.
regards
Jan Kaul