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Using dependent variable values at specific points on a boundary

Posted 10 lug 2012, 01:14 GMT-4 Fluid & Heat, Heat Transfer & Phase Change, Computational Fluid Dynamics (CFD), Parameters, Variables, & Functions Version 4.0a, Version 4.3 2 Replies

Abe Calde
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[Conjugate Heat Transfer v4.0a]
[2D Stationary study]

I want to use the temperature at two fluid-solid boundaries to generate the boundary condition of heat generation at one boundary. Something like: Flux at boundary 1 = f(T at boundary 1, T at boundary 2). Boundary 1 and 2 have the same x-location, different y-location.

I have tried defining local variables with geometric scope at the boundary (e.g. Tb1 defined as mod1.T, geom scope at Boundary 1) but when it computes for the boundary condition using Tb1 in the expression, it says that it "fails to evaluate variable".

I also want to get a point-by-point value for the boundary condition so I would not prefer integrating/averaging the temperature over each boundary.

In essence, this is a boundary condition dependent on the dependent variable (T) which is also dependent on position. How could I do this in COMSOL?

Thanks!

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Abe
2 Replies Last Post 6 set 2012, 23:14 GMT-4
COMSOL Moderator

Hello Abe Calde

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Shawn.F
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Posted: 1 decade ago 6 set 2012, 14:16 GMT-4
Abe,

I have the exact same problem, and I get the exact same error.

If you have resolve the problem, could you share the solution please?

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Shawn
Abe, I have the exact same problem, and I get the exact same error. If you have resolve the problem, could you share the solution please? -- Shawn
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 6 set 2012, 23:14 GMT-4
Hi

if your boundaries are not overlapping you need to use a projection operator to "project" the value of one boundary onto the other to be able to define an equation linkeing two fields by the boundary coordinates. See the projection operator, and try out some SIMPLE example first, once you grasp tem you will see it's easy ;)

there are also already a few examples on the forum, try a search

Another point try to get hands on a newer version v4.0 was really an "early issue" and has greatly improved since

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Good luck
Ivar
Hi if your boundaries are not overlapping you need to use a projection operator to "project" the value of one boundary onto the other to be able to define an equation linkeing two fields by the boundary coordinates. See the projection operator, and try out some SIMPLE example first, once you grasp tem you will see it's easy ;) there are also already a few examples on the forum, try a search Another point try to get hands on a newer version v4.0 was really an "early issue" and has greatly improved since -- Good luck Ivar

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