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Modeling a liquid sphere with specified normal acceleration at the boundary
Posted May 11, 2011, 8:39 p.m. EDT Acoustics & Vibrations Version 4.1 2 Replies
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We're just getting started with COMSOL and are trying to model a standing spherical wave in a 4-inch radius water sphere.
First we ran an Eigenfrequency study and successfully found several eigenfrequencies that match our independent calculations.
We then ran Pressure Acoustics with a frequency domain study. We added Normal Acceleration and set Inward Acceleration to 7700 m/s^2 on all boundaries. We set the frequency to one of the eigenfrequencies (25696 Hz). When we try to run the study we get the message "The mass matrix is zero."
Obviously we're having trouble figuring out the right approach. We'd appreciate any suggestions. I've attached the model file.
First we ran an Eigenfrequency study and successfully found several eigenfrequencies that match our independent calculations.
We then ran Pressure Acoustics with a frequency domain study. We added Normal Acceleration and set Inward Acceleration to 7700 m/s^2 on all boundaries. We set the frequency to one of the eigenfrequencies (25696 Hz). When we try to run the study we get the message "The mass matrix is zero."
Obviously we're having trouble figuring out the right approach. We'd appreciate any suggestions. I've attached the model file.
Attachments:
2 Replies Last Post May 13, 2011, 12:55 p.m. EDT
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Posted:
1 decade ago
Hi,
I don't have V4.1, but have you defined a face or a point where the sinusoidal force of the frequency analysis is applied?
Henna
I don't have V4.1, but have you defined a face or a point where the sinusoidal force of the frequency analysis is applied?
Henna
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Posted:
1 decade ago
It turns out that we somehow confused Comsol. We added the Frequency Domain study to the existing Eigenfrequency study and disabled the Eigenfrequency study. In that situation we got the error message. We started another problem with just the Frequency Domain study and didn't get the error.