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Complex Plane Analysis for Helmholtz resonators
Posted 30.06.2023, 10:48 GMT-4 Structural & Acoustics, Acoustics & Vibrations, Studies & Solvers Version 6.0 1 Reply
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Hello Everyone.
Currently I'm working on doing a transmission analysis on Helmholtz resonators. I'm using both the thermoviscous acoustics and pressure acoustics module to simulate a transmission measurement in an impedance tube setup. So far I have been able to do a frequency sweep to obtain the sound reflection coefficient in function of real frequency values. However, I want to obtain the reflection coefficient values for complex frequency values as well. So I want to do a complex plane analysis on the resonant frequency of the resonator I'm studying.
I want to obtain a 2D surface where both the x and y axis represent the real and imaginary components of the wave frequency respectively, with the surface value being the reflection coefficient. I have read the manual as well as checking the COMSOL Gallery for examples but so far I am unable to figure it out. Does anyone have an idea on how to approach this?
Thank you for reading!
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It sounds like you want to plot the transfer function a la https://www.acculution.com/single-post/2018/03/31/016-poles-and-zeros-the-real-heroes. But in your frequency setup, phasors are assumed with a complex frequency of s=0+iw, so no real part, and in the simulation software you enter w. This frequency can be negative, which will be of importance if the system in question is not real (physical), but I cannot be complex as far as I know. So if I am reading your question correctly, I don't see a way to do this in COMSOL, but I could be wrong.
-------------------René Christensen, PhD
Acculution ApS
www.acculution.com
info@acculution.com