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Moving boundary

Posted 17.01.2011, 18:58 GMT-5 Chemical Reaction Engineering, Geometry, Mesh, Studies & Solvers Version 4.1 5 Replies

Melissa Rice
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Hello all

I was trying to formulate a moving interface for my model. The interface moves because the material from the interior domain reaches the surface and reacts. The equations (diffusion) in the outer domain is different. my question was, if i try to implement the ALE method for moving my mesh at a study-controlled rate, does it mean that the equations governing the interior domain is slowly extending out into my outer domain. Or the domain equations remain the same. Thanks
5 Replies Last Post 23.10.2011, 21:37 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 18.01.2011, 05:57 GMT-5
Hi

if you have one mesh and it deforms all physics follow in my view, but if you have several meshes you might keep one stationary, check the solver geometry and mesh settings. In anycase that is typically worth a confirmation by support (and if possible relay it back here it's of general interest)

--
Good luck
Ivar
Hi if you have one mesh and it deforms all physics follow in my view, but if you have several meshes you might keep one stationary, check the solver geometry and mesh settings. In anycase that is typically worth a confirmation by support (and if possible relay it back here it's of general interest) -- Good luck Ivar
Melissa Rice
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Posted: 1 decade ago 18.01.2011, 14:15 GMT-5
Thanks for the suggestion. I will post the updates if i amnage to figure it out.
Thanks for the suggestion. I will post the updates if i amnage to figure it out.
Melissa Rice
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Posted: 1 decade ago 18.01.2011, 15:47 GMT-5
Hi Ivar - Thanks again for your suggestion. It is commendable that you take care to answer most questions here on the forum. Hats off to you! I did confirm that the physics moves with the mesh. This means that the interface is physically moving along with all the equations. However i noticed that when i move the mesh, there are inverted meshes as a result of huge deformations. Is there any way around this, where i can still move my interface and not have inverted mesh elements. Quite frankly, this problem does not interfere with the solution and I wonder why the problem is notified in the first place. Thanks
Hi Ivar - Thanks again for your suggestion. It is commendable that you take care to answer most questions here on the forum. Hats off to you! I did confirm that the physics moves with the mesh. This means that the interface is physically moving along with all the equations. However i noticed that when i move the mesh, there are inverted meshes as a result of huge deformations. Is there any way around this, where i can still move my interface and not have inverted mesh elements. Quite frankly, this problem does not interfere with the solution and I wonder why the problem is notified in the first place. Thanks
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 18.01.2011, 16:07 GMT-5
Hi

indeed moving mesh is delicate for large deformations. There are several tricks, you can find some in th KB. The best is really to follow some of the COMSOL 1 day courses, there even one specifically for the advanced meshing such as ALE. Really it's more than a full days explanations. So start check and read the doc carefully (4.1, or 3.5a) on ALE and do some of the exercices from the model library. An inverted mesh here and there is not catastrophic, so long there are a few, normally COMSOL switches to linear shape function for these and manage to continue. There are also "remesh options", (was in 3.5a, havent tried nor know exactly where in v4.1, probably deep in the solver settings ;)
--
Good luck
Ivar
Hi indeed moving mesh is delicate for large deformations. There are several tricks, you can find some in th KB. The best is really to follow some of the COMSOL 1 day courses, there even one specifically for the advanced meshing such as ALE. Really it's more than a full days explanations. So start check and read the doc carefully (4.1, or 3.5a) on ALE and do some of the exercices from the model library. An inverted mesh here and there is not catastrophic, so long there are a few, normally COMSOL switches to linear shape function for these and manage to continue. There are also "remesh options", (was in 3.5a, havent tried nor know exactly where in v4.1, probably deep in the solver settings ;) -- Good luck Ivar
Sanket Kelkar
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Posted: 1 decade ago 23.10.2011, 21:37 GMT-4
Hi Melissa, Can you share your file? I am having similar problems.
Hi Melissa, Can you share your file? I am having similar problems.

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