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Micro Valve

Posted Apr 11, 2011, 4:35 a.m. EDT Computational Fluid Dynamics (CFD) Version 3.5a 4 Replies

Amer Malik
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Hey,

I am trying to simulate a micro valve. So I have to model a contact pair with fluid flowing between the two contacting bodies. The bodies are initially at a distance and after a while they touch each other and stop the fluid flow.

Now when I solve this time dependent problem, after a while the mesh (to solve for the fluid flow) between the contacting bodies gets distorted as the bodies come closer and the solution diverges. Is there any solution to solve such problem? Any suggestion?

/ Amer
4 Replies Last Post Apr 11, 2011, 6:36 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Apr 11, 2011, 5:04 a.m. EDT
Hi

yes there are a few, as the "guiding lines" for ALE or the deformation type settings in the solver, these are briefly described in the KB, far better during the advanced meshing course of COMSOL.

One important thing though for your case, if your two solids come in contact you are changing the topology and adding a common boundary.
This is not understood by COMSOL as it would require a boundary id renumbering.

My way around is to enforce a small minimum gap to allow some squeezed mesh elements in between this ensures the continuity of the fluid domain, which should in no case "disappear". But this prevents your model to fully "close" the valve

--
Good luck
Ivar
Hi yes there are a few, as the "guiding lines" for ALE or the deformation type settings in the solver, these are briefly described in the KB, far better during the advanced meshing course of COMSOL. One important thing though for your case, if your two solids come in contact you are changing the topology and adding a common boundary. This is not understood by COMSOL as it would require a boundary id renumbering. My way around is to enforce a small minimum gap to allow some squeezed mesh elements in between this ensures the continuity of the fluid domain, which should in no case "disappear". But this prevents your model to fully "close" the valve -- Good luck Ivar
John
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Posted: 1 decade ago Apr 11, 2011, 4:36 p.m. EDT
You might want to check out this example on mesh deformation techniques: www.comsol.com/support/knowledgebase/970/

I can't comment too much beyond that for version 3.5a. In general, you need to be careful about your boundary conditions as the contact pair can conflict with the fluid flow boundary conditions (at least in 4.1).

~John
You might want to check out this example on mesh deformation techniques: http://www.comsol.com/support/knowledgebase/970/ I can't comment too much beyond that for version 3.5a. In general, you need to be careful about your boundary conditions as the contact pair can conflict with the fluid flow boundary conditions (at least in 4.1). ~John
Amer Malik
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Posted: 1 decade ago Apr 11, 2011, 5:15 p.m. EDT
Thanks for the replies.

Ivar, is there a way to enforce a small minimum gap between the two contacting bodies? This is not gonna solve my problem but this would at least act as the valve is 'closed'. And, yes if two solids will come in contact, this will change the topology, but isn't that how Contact Pairs constraint works?

Yes John, I have checked that tutorial already and that was really helpful. But the problem, as Ivar mentioned, is the squeezed elements between the contacting bodies. Of course they can not 'disappear' so there has to be some fluid flow even when the valve is 'closed'.

P.S: Ivar, what is KB in "briefly described in the KB"?

/ Amer
Thanks for the replies. Ivar, is there a way to enforce a small minimum gap between the two contacting bodies? This is not gonna solve my problem but this would at least act as the valve is 'closed'. And, yes if two solids will come in contact, this will change the topology, but isn't that how Contact Pairs constraint works? Yes John, I have checked that tutorial already and that was really helpful. But the problem, as Ivar mentioned, is the squeezed elements between the contacting bodies. Of course they can not 'disappear' so there has to be some fluid flow even when the valve is 'closed'. P.S: Ivar, what is KB in "briefly described in the KB"? / Amer
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Apr 11, 2011, 6:36 p.m. EDT
Hi

KB is (my jargon for) the main web site "Support Knowledge Base" see

www.comsol.eu/support/knowledgebase/browse/900/


There is indeed an "gap parameter" in the settings at least in V4.1 (cannot remember anylonger if/where it was in 3.5, sorry for that)


--
Good luck
Ivar
Hi KB is (my jargon for) the main web site "Support Knowledge Base" see http://www.comsol.eu/support/knowledgebase/browse/900/ There is indeed an "gap parameter" in the settings at least in V4.1 (cannot remember anylonger if/where it was in 3.5, sorry for that) -- Good luck Ivar

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