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Implementing Periodic Boundary Conditions in Coefficient Form Boundary PDEs

Posted 27 mars 2017, 23:08 UTC−4 Modeling Tools & Definitions, Parameters, Variables, & Functions Version 5.2a, Version 5.3 4 Replies

Simantini Mitra-Behura
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I'm attempting to model a Coefficient Form Boundary PDE on the surface of a 3D model. I would like to impose periodic boundary conditions on the two edges of the boundary; however, it does not appear that COMSOL supports periodic boundary conditions for Boundary PDE's by default. I have attempted to fix this by creating a linear extrusion from edge #1 to edge #2, and then setting Dirichlet boundary conditions on edge #2 equal to the value at edge #1, but this only sets the values, and not the derivatives, equal to each other. I don't see any clear way to set the derivatives equal to each other - attempting a similar approach with a flux/source boundary condition at edge #2 with dtang won't work, as the value on the edge consistently evaluates to some value on the order of 10^-13. Is there any way to do this, or a simpler way in general to impose periodic boundary conditions on coefficient form boundary PDEs?
4 Replies Last Post 14 août 2017, 07:04 UTC−4
Simantini Mitra-Behura
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Posted: 8 years ago 29 mars 2017, 10:28 UTC−4
Does anyone have any suggestions? It appears as though the normal d() operator is not defined on edges, and the dtang() operator seems to give more sensical answers evaluated on the boundary rather than on the edge itself.
Does anyone have any suggestions? It appears as though the normal d() operator is not defined on edges, and the dtang() operator seems to give more sensical answers evaluated on the boundary rather than on the edge itself.
Chenghao Cao
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Posted: 7 years ago 4 juil. 2017, 22:21 UTC−4

Does anyone have any suggestions? It appears as though the normal d() operator is not defined on edges, and the dtang() operator seems to give more sensical answers evaluated on the boundary rather than on the edge itself.


I met the same problems like you. So we can talk about this problem,OK?
My email is abcd702848@hhu.edu.cn
[QUOTE] Does anyone have any suggestions? It appears as though the normal d() operator is not defined on edges, and the dtang() operator seems to give more sensical answers evaluated on the boundary rather than on the edge itself. [/QUOTE] I met the same problems like you. So we can talk about this problem,OK? My email is abcd702848@hhu.edu.cn
Chenghao Cao
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Posted: 7 years ago 24 juil. 2017, 22:08 UTC−4

I'm attempting to model a Coefficient Form Boundary PDE on the surface of a 3D model. I would like to impose periodic boundary conditions on the two edges of the boundary; however, it does not appear that COMSOL supports periodic boundary conditions for Boundary PDE's by default. I have attempted to fix this by creating a linear extrusion from edge #1 to edge #2, and then setting Dirichlet boundary conditions on edge #2 equal to the value at edge #1, but this only sets the values, and not the derivatives, equal to each other. I don't see any clear way to set the derivatives equal to each other - attempting a similar approach with a flux/source boundary condition at edge #2 with dtang won't work, as the value on the edge consistently evaluates to some value on the order of 10^-13. Is there any way to do this, or a simpler way in general to impose periodic boundary conditions on coefficient form boundary PDEs?

I think one more constraint is necessary
[QUOTE] I'm attempting to model a Coefficient Form Boundary PDE on the surface of a 3D model. I would like to impose periodic boundary conditions on the two edges of the boundary; however, it does not appear that COMSOL supports periodic boundary conditions for Boundary PDE's by default. I have attempted to fix this by creating a linear extrusion from edge #1 to edge #2, and then setting Dirichlet boundary conditions on edge #2 equal to the value at edge #1, but this only sets the values, and not the derivatives, equal to each other. I don't see any clear way to set the derivatives equal to each other - attempting a similar approach with a flux/source boundary condition at edge #2 with dtang won't work, as the value on the edge consistently evaluates to some value on the order of 10^-13. Is there any way to do this, or a simpler way in general to impose periodic boundary conditions on coefficient form boundary PDEs? [/QUOTE] I think one more constraint is necessary
Petri Hirvonen
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Posted: 7 years ago 14 août 2017, 07:04 UTC−4
Hi,

I would also like to implement periodic boundary conditions in my coefficient form boundary PDE model. Did either of you figure out how to achieve this? Anybody else?

-Pete
Hi, I would also like to implement periodic boundary conditions in my coefficient form boundary PDE model. Did either of you figure out how to achieve this? Anybody else? -Pete

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