I'm trying to build a finite element model for an acoustic metamaterial, where losses play an important role. However, I'm having some trouble when combining the thermoacoustics physics with Floquet boundary conditions.
In the case of the pressure acoustics model, the system predicts resonance frequencies that are in reasonable agreement with the experiements. However, when using pressure acoustics the resonances completely change. I'm using a boundary layer mesh with 8 levels and considerable resolution, and refining the mesh further doesn't seem to impact the results.
Any idea what may be going on?
Attached a comparison between pressure acoustics and thermoacoustics.