Defining the area of a 2d domain with an ODE

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Just as the title asks. I am trying to model the pressure waves caused by the expansion and contraction of an underwater bubble-like object through a net-like solid structure as a pressure wave passes over the entire area. It is not a domain that I can simply define as, for example, a sphere where the mesh boundary could be defined via velocity or simple geometric expansion around a point. It almost is a geometric expansion around a point besides the structure that is in the way.

I have the derived the ODE that allows me to define this object via area/volume. But I am having a hard time finding a way in COMSOL to define the explicit volume of a domain directly.

https://www.comsol.com/blogs/computing-controlling-volume-cavity is the closest I can find but for my example the pressure change will not need to be calculated, it is included in my ODE. This is a problem that is fairly simple when there is no object in the way as I have read other examples of them defining the expansion of bubble like objects in terms of the wall-velocity calculated via the rayleigh-plesset equation, or even simpler as defining the radius of the domain etc. But as the expansion I want to study is by virtue of the solid object unable to act as a simple radially symmetric breathing mode for my results I would be best served by defining the volume programatically.

If anyone has any experience in defining the volume of a domain using an ODE, a PDE or just directly using another means of defining the changing volume of a domain please offer advice.

Best, Luke


1 Reply Last Post 18 set 2026, 16:32 GMT-4
Jeff Hiller COMSOL Employee

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Posted: 1 hour ago 18 set 2026, 16:32 GMT-4

Hi Luke,

I am having trouble understanding this. A sketch might help. BTW, Are the deformations of the bubble-like object known a priori? or are they a result of your simulation? What are the knowns, and what are the unknowns here?

Best,

Jeff

PS: Generally, volumes/surfaces are computed by integration (i.e. using a coupling operator), not via ODEs.

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Jeff Hiller
Hi Luke, I am having trouble understanding this. A sketch might help. BTW, Are the deformations of the bubble-like object known a priori? or are they a result of your simulation? What are the knowns, and what are the unknowns here? Best, Jeff PS: Generally, volumes/surfaces are computed by integration (i.e. using a coupling operator), not via ODEs.

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