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Subdomain integration

Posted 1 mars 2010, 05:04 UTC−5 5 Replies

Joanne Wilson
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Hi all,

I have a 2D transient model involving convection-diffusion equation. The sub-domain concentration is continuously evolving over time. The problem is, I need to find the total concentration in a particular region inside the sub domain and then use that value to vary the boundary parameters over time. I cannot specify that particular region as a sub-domain because this region's position is also continuously changing over time. The problem is two fold, first: how to address/specify a region inside a subdomain using x,y and t values? Secondly how to extract the solution in that particular region and add the values and then use it as boundary input?

Hope I stated my problem clearly. Kindly ask me if it needs further explanation.

Thanks a bunch,

Jo
5 Replies Last Post 1 mars 2010, 22:20 UTC−5
Jean-Francois Leon
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Posted: 1 decade ago 1 mars 2010, 05:13 UTC−5
why you cannot define the region as a moving subdomain using ale feature?
why you cannot define the region as a moving subdomain using ale feature?
Joanne Wilson
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Posted: 1 decade ago 1 mars 2010, 05:27 UTC−5
Hi Jean,

Thanks for the reply.
I cannot specify the region as moving subdomain because the size and shape of the region is also continuously changing. Ok. I ll try to explain the problem more clearly.

I have a 2d domain and I am moving the boundary of the domain over time using 'ale'. As the boundary is moving the volume of the domain is shrinking. When you think about it, when the domain is shrinking the concentration(moles/m3) inside the domain should be increasing, but this doesn't happen automatically due to 'ale'. So now I have to add the no of moles that was in the 'volume that shrunk' every time step artificially as inflow flux. How can I do that?.

Cheers,
Jo
Hi Jean, Thanks for the reply. I cannot specify the region as moving subdomain because the size and shape of the region is also continuously changing. Ok. I ll try to explain the problem more clearly. I have a 2d domain and I am moving the boundary of the domain over time using 'ale'. As the boundary is moving the volume of the domain is shrinking. When you think about it, when the domain is shrinking the concentration(moles/m3) inside the domain should be increasing, but this doesn't happen automatically due to 'ale'. So now I have to add the no of moles that was in the 'volume that shrunk' every time step artificially as inflow flux. How can I do that?. Cheers, Jo
Jean-Francois Leon
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Posted: 1 decade ago 1 mars 2010, 05:34 UTC−5
I dont understand if you resolve the equation inside the said domain i the moving frame you conserve mass and increase convcentration.
On which frame do you solve your equations inside the domain the reference frame or the moving frame?


I am not [ BY FAR] an expert on Comsol but I have solved a problem where a bubble gas was compressed and deformed using ale technique and the pressure augmented and the mass was conserved...
I dont understand if you resolve the equation inside the said domain i the moving frame you conserve mass and increase convcentration. On which frame do you solve your equations inside the domain the reference frame or the moving frame? I am not [ BY FAR] an expert on Comsol but I have solved a problem where a bubble gas was compressed and deformed using ale technique and the pressure augmented and the mass was conserved...
Joanne Wilson
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Posted: 1 decade ago 1 mars 2010, 21:02 UTC−5
I am not sure if the mass is conserved in my case. May be I am doing something wrong. I ll check on that. Anyways is there a way I can get sub domain integration values during the solution. i.e I need to feed the subdomain integral value of one time step as the input to the next time step?
I am not sure if the mass is conserved in my case. May be I am doing something wrong. I ll check on that. Anyways is there a way I can get sub domain integration values during the solution. i.e I need to feed the subdomain integral value of one time step as the input to the next time step?
Karthik K
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Posted: 1 decade ago 1 mars 2010, 22:20 UTC−5
Refer 'Integration Coupling Variables' help file.

Options> integration coupling variables > subdomain

You just have to specify the variable to be integrated and the domain to be integrated and the value can be made available globally and you can use it at any time point during the solution.
Refer 'Integration Coupling Variables' help file. Options> integration coupling variables > subdomain You just have to specify the variable to be integrated and the domain to be integrated and the value can be made available globally and you can use it at any time point during the solution.

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