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Moving boundary

Posted 27 juin 2012, 10:33 UTC−4 Fluid & Heat, Heat Transfer & Phase Change, Geometry, Mesh, Modeling Tools & Definitions, Parameters, Variables, & Functions, Studies & Solvers Version 4.2a 2 Replies

Reza
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HI

The attachment is a simple model of my problem, first I solve a Poisson's equation on the circles and secondly I would like to move the boundaries with the velocity field (ux/2,uy/2). After the movement I would like to extract the new geometry and do the same steps till the gradient vanishes on the boundary but these two circles are fixed in all steps. I have tried moving mesh(ale), deform geometry(dg) and level set but have got stuck. I wonder which method is better?
Any suggestion?
You can also consider the two fixed balls as the injection of two fluids(same fluid, or even two heat sources) and we desire to follow the boundary of occupied region after the fluids meet each other.
For more information see pdf file.

Best, Reza
2 Replies Last Post 27 juin 2012, 12:53 UTC−4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 27 juin 2012, 11:04 UTC−4
Hi

I have some problems to follow your model: your 2 circles are touching via a point, but how do you define a continuity over a singularity of a point ?, you cannot balance your flux.

For me you need to have a true boundary (=edge in 2D) common between the two items

then I'm still not understanding how you can with simple Poisson equation get the two domains to interact if one is moving w.r.t. the other. what are the boundary conditions between the now not touching, but will be touching boundaries.

this is what you find behind COMSOL Contact physics, it's far from trivial, but certainly interesting to learn how to set-up

--
Good luck
Ivar
Hi I have some problems to follow your model: your 2 circles are touching via a point, but how do you define a continuity over a singularity of a point ?, you cannot balance your flux. For me you need to have a true boundary (=edge in 2D) common between the two items then I'm still not understanding how you can with simple Poisson equation get the two domains to interact if one is moving w.r.t. the other. what are the boundary conditions between the now not touching, but will be touching boundaries. this is what you find behind COMSOL Contact physics, it's far from trivial, but certainly interesting to learn how to set-up -- Good luck Ivar
Reza
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Posted: 1 decade ago 27 juin 2012, 12:53 UTC−4
Dear Ivar

Thank you for your interest. I have explained more about the problem in the pdf file. I also have updated the comsol file. Please have a look.

Thank you again.
Best, Reza
Dear Ivar Thank you for your interest. I have explained more about the problem in the pdf file. I also have updated the comsol file. Please have a look. Thank you again. Best, Reza

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