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Re: Moving Boundaries Problem (ALE) / Inverted Mesh Warnings
Posted Feb 5, 2011, 4:31 a.m. EST 3 Replies
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Hi,
I am working on a 1-D moving boundaries problem using ALE application mode. In this model, two boundaries are moving on one side with different velocities.
Let me explain clearly with number. Consider 3 boundaries, where the first boundary is fixed. Second and third boundaries are moving towards the first. Here, the third boundary is moving with a higher velocity than the second one. So, I set up a if condition such that it can use it's own velocity until it hits the second boundary and then the third boundary must use the velocity of the second one. So that both boundaries move together.
When i tried to model the above mentioned problem, I got inverted mesh warnings. I have tried several things...for example, allowing a definite (small) distance between the second boundary and the third one. so that i can get rid of inverted mesh warnings. but unsucessful.
Can i build a model in COMSOL where two domains collapse into one after a certain time?
Any suggestions/comments are greatly appreciated.
Thank you,
Manohar
I am working on a 1-D moving boundaries problem using ALE application mode. In this model, two boundaries are moving on one side with different velocities.
Let me explain clearly with number. Consider 3 boundaries, where the first boundary is fixed. Second and third boundaries are moving towards the first. Here, the third boundary is moving with a higher velocity than the second one. So, I set up a if condition such that it can use it's own velocity until it hits the second boundary and then the third boundary must use the velocity of the second one. So that both boundaries move together.
When i tried to model the above mentioned problem, I got inverted mesh warnings. I have tried several things...for example, allowing a definite (small) distance between the second boundary and the third one. so that i can get rid of inverted mesh warnings. but unsucessful.
Can i build a model in COMSOL where two domains collapse into one after a certain time?
Any suggestions/comments are greatly appreciated.
Thank you,
Manohar
3 Replies Last Post Feb 5, 2011, 6:47 a.m. EST
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Posted:
1 decade ago
Hi
One advice: be sure that the "third" point (boundary) NEWVER comes all the way up to the second, because then you remove a domain (=line in 1D) and that is a topological change that COMSOL cannot cope with as the domain id's are renumbered etc. Normally the ALE should work OK so long you do not change the topology, so leave this last line lengt ther but with a "small" value.
Still you might need to tweak a little the ALE settings to help the system to have a regular contraction of all nodes along the line.
For me I do expect your model to work well, if you respct the point above
--
Good luck
Ivar
One advice: be sure that the "third" point (boundary) NEWVER comes all the way up to the second, because then you remove a domain (=line in 1D) and that is a topological change that COMSOL cannot cope with as the domain id's are renumbered etc. Normally the ALE should work OK so long you do not change the topology, so leave this last line lengt ther but with a "small" value.
Still you might need to tweak a little the ALE settings to help the system to have a regular contraction of all nodes along the line.
For me I do expect your model to work well, if you respct the point above
--
Good luck
Ivar
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Posted:
1 decade ago
Hi Ivar,
Thanks for your reply. I actually tried the same thing by leaving a small distance between the second and the third one, but still i am getting a lot of inverted mesh warnings.
Sorry i forgot to mention that initially there is a 4 orders of magnitude difference between the two domains. I just want to see how a reactant particle converts into product. So initially i used a small 2nd domain (i.e. products).
I meshed differently with interactive meshing to see if it works. But even that didn't helped.
Any ideas on how can i model this problem with out having any inverted mesh warnings.
Thanks
Thanks for your reply. I actually tried the same thing by leaving a small distance between the second and the third one, but still i am getting a lot of inverted mesh warnings.
Sorry i forgot to mention that initially there is a 4 orders of magnitude difference between the two domains. I just want to see how a reactant particle converts into product. So initially i used a small 2nd domain (i.e. products).
I meshed differently with interactive meshing to see if it works. But even that didn't helped.
Any ideas on how can i model this problem with out having any inverted mesh warnings.
Thanks
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Posted:
1 decade ago
Hi
yuo have the "remeshing" option as one thing, i.e. check the mesh size and remesh or remeah systematically
but also the ALE mesh laws: "You can choose between Laplace smoothing, Winslow smoothing, and hyperelastic smoothing"
Not sure which one to propose though
--
Good luck
Ivar
yuo have the "remeshing" option as one thing, i.e. check the mesh size and remesh or remeah systematically
but also the ALE mesh laws: "You can choose between Laplace smoothing, Winslow smoothing, and hyperelastic smoothing"
Not sure which one to propose though
--
Good luck
Ivar