Simulation of pneumatic muscle in comsol

Thu, 20 Oct 2011 19:00:05 +0000

Hello all,
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I want to simulate an artificial pneumatic muscle which has a simple cylindrical geometry initially. When the muscle is inflated with fluid/air…it will expand in the midsection (inflate in transverse direction) causing to contract in longitudinal direction. I was wondering if “Fluid structural interaction” can be used for this purpose. If not what are the options?
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Another thing is, the domain would have and inlet without any outlet. The fluid would accumulate inside the volume causing it to inflate in transverse direction producing a contraction in longitudinal direction. I would really appreciate any guidance or suggestion from the community.
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Eigenfrequency Analysis in Fluid-Structure Interaction

Fri, 25 Jun 2010 09:39:31 +0000

I'm trying to calculate the resonance frequencies of a fluid filled hollow shell and the results I get are NaN for each frequency, but it works when I use the Pressure-Acoustics (acpr) physics mode (I get frequencies and realistic mode shapes) on some arbitrary shape.

Here is my setup process (using Acoustics Module in version 4.0)<check attached file for further clarification>:

Load physics and the liquid water material. Load the Linear Elastic Material Model (from the physics tree "branch")

Draw two concentric spheres, set the outer one as solid elastics model, leave the inner as acoustics pressure.

From the Union.

Acoustic-Structure boundary is automatically assigned to their interface (8 surfaces)

Set material properties (Young's Modulus, Poisson Ratio, Density and get three green checks) manually in the solid outer sphere.

Do a normal Free mesh and then compute 18 or so eigenfrequencies.

Everything else was left to default

This results in all NaNs.

From my understanding, the computer now knows everything it needs to calculate the frequencies: forces and accelerations from material properties; geometrical relationships in the functions; and the mesh. It knows what part is fluid, what part is solid so I don't understand why its not working. It might be something in the solver

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Simulation of pneumatic muscle in comsol

Eigenfrequency Analysis in Fluid-Structure Interaction