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Mode shapes for a 3D cylindrical structure in 4.3b

Posted Dec 8, 2014, 6:07 p.m. EST Structural Mechanics 0 Replies

Rebecca Clemens
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I have a couple of questions about a model of an open-ended simply-supported cylinder I'm running to get eigenfrequencies to compare to values I calculated analytically for the same structure. I've gotten some really good matching frequencies (<1% difference), but I'm curious about COMSOL's results.

When I look at the 3D plot of each eigenfrequency, I see that the n mode counts (axial wavelengths) match my analytical values exactly. The m mode counts (circumferential half-waves), however, vary wildly and randomly. Out of 100 calculated eigenfrequencies in the range of 340 - 2500 Hz, only 3 results have the same m value as the analytical.

1) Is there any explanation for this?

The closely-matched frequencies came from a structural/solid model, with prescribed displacement to emulate simply-supported. I had run a shell with pinned boundary conditions, but the eigenfrequencies didn't match up with my analytical.

2) Is there a way to get a list or table of the m & n values for each eigenfrequency? Looking at each plot & counting is really tedious.

Thank you for any assistance with this,
Rebecca
0 Replies Last Post Dec 8, 2014, 6:07 p.m. EST
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Hello Rebecca Clemens

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