Shape optimization leading to singular matrix in BEM

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Hi,

I'm trying out shape optimization for acoustics and it seems to work nicely in FEM. Building the same models with BEM however, I get the "singular matrix" error after adding the shape optimization stuff in.

To counteract the possible underconstriction, I tried adding in stuff like another free shape domain on the outside of the free shape boundary, roller/symmetry for the boundary on the symmetry plane and fixed edge around the free shape domain but those didn't help. Also checked the material assignment ten times. I went through pretty much all the settings though I hardly understand a fraction of them, lol

Model attached



2 Replies Last Post Dec 11, 2024, 8:05 a.m. EST
Kristian Ejlebjærg Jensen COMSOL Employee

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Posted: 2 weeks ago Dec 11, 2024, 4:52 a.m. EST

Hi Tuukka

There is a warning under the Compile Equations feature saying that the domain is not meshed. This is the immediate reason for the singular matrix, i.e. there is no volume mesh for the Free Shape Domain. You can avoid the need for a volume mesh by using a Free Shape Shell feature, but adjoint sensitivity is not supported for BEM in COMSOL 6.3 (latest version in time of writing), so you will have to try and solve your problem using FEM.

Best regards,

Kristian E. Jensen

Technical Product Manager, Optimization

Hi Tuukka There is a warning under the Compile Equations feature saying that the domain is not meshed. This is the immediate reason for the singular matrix, i.e. there is no volume mesh for the Free Shape Domain. You can avoid the need for a volume mesh by using a Free Shape Shell feature, but adjoint sensitivity is not supported for BEM in COMSOL 6.3 (latest version in time of writing), so you will have to try and solve your problem using FEM. Best regards, Kristian E. Jensen Technical Product Manager, Optimization

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Posted: 2 weeks ago Dec 11, 2024, 8:05 a.m. EST
Updated: 2 weeks ago Dec 11, 2024, 8:05 a.m. EST

Thanks, things make sense now! Are there any plans for the implementation (or workarounds)? Seems like quite a bit of "wasted" potential

Thanks, things make sense now! Are there any plans for the implementation (or workarounds)? Seems like quite a bit of "wasted" potential

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