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## Subdomain integration

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 Mar 1, 2010, 10:20 p.m. EST

why you cannot define the region as a moving subdomain using ale feature?

Hi Jean,

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

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...