COMSOL - Plane Wave Radiation input not matching Pressure Field

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SUMMARY

The forum discussion centers on a COMSOL model configured as a cuboid with a membrane, resembling an impedance tube setup. The user implemented Integration 1 & 2 and Explicit 1 & 2 to establish inlet and outlet conditions, with an inlet pressure amplitude set to 20 Pa. However, the resulting acoustic pressure at the first eigenfrequency is unexpectedly low, measuring approximately 1x10^-11 Pa. This discrepancy raises questions about the accuracy of the Plane Wave Radiation input and its effect on the pressure field.

PREREQUISITES
  • Familiarity with COMSOL Multiphysics, specifically acoustic modeling.
  • Understanding of pressure fields and eigenfrequencies in acoustics.
  • Knowledge of integration techniques within COMSOL, particularly Integration 1 & 2.
  • Experience with defining boundary conditions in simulation software.
NEXT STEPS
  • Investigate the configuration of Plane Wave Radiation in COMSOL for accurate pressure field representation.
  • Review the implementation of Integration 1 & 2 and Explicit 1 & 2 to ensure correct inlet and outlet definitions.
  • Explore the effects of eigenfrequency on acoustic pressure measurements in COMSOL.
  • Consult COMSOL documentation on troubleshooting pressure discrepancies in acoustic models.
USEFUL FOR

Acoustic engineers, COMSOL users, and researchers involved in modeling sound propagation and pressure fields in fluid dynamics.

pitchtwit
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I have a model set up, that is a cuboid, with a membrane half-way along - a bit like an impedance tube setup.

I've used Integration 1 & 2 with Explicit 1 & 2 to define an 'inlet' and 'outlet' at opposing faces of the tube. The Variables for the inlet and outlet are intop1(p0) and intop2(p).

I then added Plane Wave Radiation to the model (inlet & outlet), with the Incident Pressure Field on just the inlet set with a Pressure Amplitude p0 = 20 Pa.

The resulting Acoustic Pressure at the 1st Eigenfrequency shows that the flow direction is correct, but the scale is odd. It shows that the pressure at the inlet is about 1x10^-11 Pa.

How can this be, when I set the inlet pressure to be 20 Pa?

Many thanks.

https://dl.dropboxusercontent.com/u/11341635/Screen%20Shot%202014-08-12%20at%2008.35.20.png
 
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