I have modelled a unit-cell of an anechoic structure using ANSYS. The layer is silicone and has been assigned as an acoustics physics region, with an air cavity inside (the air has been modelled and also assigned as an acoustics physics region). There is a steel backplate as well that is structural. In order to simulate the water closure on the silicone layer face I have applied an impedance boundary condition, assigned a port to this front surface and used the body of the same layer to assign the inside surface bodies. A planar wave has been applied using a 'port in duct' excitation condition (with 10000 Pa) and the acoustic absorbance is calculated.
I have used the same material parameters that I have seen in many papers, however I am getting very different results and wondered if anybody could please highlight where I have modelled it incorrectly or explain the observed behaviour? I have included an image of the absorption coefficient with regards to frequency in a 0-6000 kHz range.
Thank you for any help.
Hi
A hand sketch or similar of the setup would help.
Impedance BC only apply for normal angle of incidence. They work on boundaries at a distance from the source, say one wavelength out or so and then, still are reflecting.
As per usual - the advice when tweaking models - start with simulating a Kundt's tube experiment first, as you there can use impedance BCs. Move to 3d from there.
/C
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