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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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Weak Constraints from COMSOL 3.5 to 4.2a

Posted 2013年7月15日 GMT-4 18:01 MEMS & Nanotechnology, Fluid & Heat, MEMS & Piezoelectric Devices, Microfluidics Version 4.2a 3 Replies

Gopinath Danda
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Hi

I have seen many posts regarding this but none had any definite answer.

I am trying to follow a tutorial which involving Stoke's flow, and have the following problems:

1. "Go to Properties of mmglf model and turn Weak constraints -> On and Constraint type -> Nonideal"

I have found out that the mmglf module is the same as spf module of 4.2a with the Stoke's flow check box checked. I have also found out that I can add a "Weak Constraint" node to the spf module. But I don't know if this should be the volume "Weak Contraint" node or the surface one. Also in the node, Contraint type can be set either to "Bidirectional" or "User-defined" (not Unidirectional which is non-ideal). How do I set it to "Nonideal"?

Note: "Nonideal Weak Constraint" is used to automatically calculate the hydrodynamic stress on the particle surface.

2. "Options Menu | Expressions | Boundary Expressions"

How do I write Boundary Expressions? I feel Coupling Variables is to be used, but I am not sure how. I was only able to find Integration/Summation to the boundaries.

Please help. Relevant images are attached.




3 Replies Last Post 2013年9月19日 GMT-4 11:50
COMSOL Moderator

Hello Gopinath Danda

Your Discussion has gone 30 days without a reply. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help.

If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base.

Mao Mao
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Posted: 1 decade ago 2013年9月12日 GMT-4 15:13
Hi,

Have you figure it out? I am also very interested in this topic. Lemme know if you have made progress, please.

Cheers,

Mao
Hi, Have you figure it out? I am also very interested in this topic. Lemme know if you have made progress, please. Cheers, Mao
Gopinath Danda
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Posted: 1 decade ago 2013年9月12日 GMT-4 18:20
Unfortunately no. :(

I will surely post here if I find out something regarding this. Thanks.
Unfortunately no. :( I will surely post here if I find out something regarding this. Thanks.
Mao Mao
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Posted: 1 decade ago 2013年9月19日 GMT-4 11:50
Hi Gopinath,

A little update.

The weak constraints should be applied on the boundaries. If you can select 'non-ideal', select it; if not, the 'non-ideal' is by default (what they say from the documentation).

For the boundary expressions, you can define variables on the corresponding boundaries in "Definition".

Also please lemme know if you have any experience with the remeshing.

Cheers,

Mao
Hi Gopinath, A little update. The weak constraints should be applied on the boundaries. If you can select 'non-ideal', select it; if not, the 'non-ideal' is by default (what they say from the documentation). For the boundary expressions, you can define variables on the corresponding boundaries in "Definition". Also please lemme know if you have any experience with the remeshing. Cheers, Mao

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