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Vibrating Cantilever Beam in Air using the FSI Module
Posted 21.02.2012, 18:54 GMT-5 Computational Fluid Dynamics (CFD), Mesh, Studies & Solvers, Structural Mechanics Version 4.2 1 Reply
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Hi,
I am currently trying to simulate the airflow from a piezoelectric fan using the COMSOL FSI module (v4.2). I am doing this by modeling an oscillating cantilever beam in air, and running a time dependent study. My boundary conditions are:
1. A boundary load on the cantilever tip with a sinusoidal function @ 60Hz
2. Open Boundaries on the outer edges of the fluid
I've managed to get this study working on just a cantilever beam (under the Structural Mechanics Module) to simulate the deflection of the beam. The time dependent solver configuration consists of:
1. 100 time steps per cycles for 30 cycles @ 60Hz. (i.e. range(0,1/6000,30/60)
2. BDF Strict & Intermediate Solver
However, when I attempt to run the simulation under the FSI module, I keep getting inverted element warnings which result to a failure to converge during Segregated Step 3 (fluid) of the solver. (As a note, I have successfully run through the FSI example) When I try to visualize the inverted elements, they do not show up, which leads me to believe the inverted elements are of higher order. This is confirmed when using Automatic Remeshing, as a failure to get initial conditions occurs during remeshing even with various (0.1-0.6) minimal mesh requirements. The error/failure usually occurs when the beam tip begins to have larger deformations. I have tried the following with no avail:
1. Different meshes for the deformed mesh (free triangle, free quad, coarse, fine, uniform)
2. Both the Winslow and Hypereleastic smoothing
3. Built-in Automatic resmeshing
I have searched most of the COMSOL forums for answers and am currently stuck. I am looking for some support in solving this issue of inverted elements in the fluid due to large deformations. Are there meshing methods I can utilize to prevent this issue? I can send/post my model if that can help.
Thanks in advance!
I am currently trying to simulate the airflow from a piezoelectric fan using the COMSOL FSI module (v4.2). I am doing this by modeling an oscillating cantilever beam in air, and running a time dependent study. My boundary conditions are:
1. A boundary load on the cantilever tip with a sinusoidal function @ 60Hz
2. Open Boundaries on the outer edges of the fluid
I've managed to get this study working on just a cantilever beam (under the Structural Mechanics Module) to simulate the deflection of the beam. The time dependent solver configuration consists of:
1. 100 time steps per cycles for 30 cycles @ 60Hz. (i.e. range(0,1/6000,30/60)
2. BDF Strict & Intermediate Solver
However, when I attempt to run the simulation under the FSI module, I keep getting inverted element warnings which result to a failure to converge during Segregated Step 3 (fluid) of the solver. (As a note, I have successfully run through the FSI example) When I try to visualize the inverted elements, they do not show up, which leads me to believe the inverted elements are of higher order. This is confirmed when using Automatic Remeshing, as a failure to get initial conditions occurs during remeshing even with various (0.1-0.6) minimal mesh requirements. The error/failure usually occurs when the beam tip begins to have larger deformations. I have tried the following with no avail:
1. Different meshes for the deformed mesh (free triangle, free quad, coarse, fine, uniform)
2. Both the Winslow and Hypereleastic smoothing
3. Built-in Automatic resmeshing
I have searched most of the COMSOL forums for answers and am currently stuck. I am looking for some support in solving this issue of inverted elements in the fluid due to large deformations. Are there meshing methods I can utilize to prevent this issue? I can send/post my model if that can help.
Thanks in advance!
1 Reply Last Post 21.02.2012, 20:57 GMT-5
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Posted:
1 decade ago
Hi.
I also had this same problem. I was advised to use step function. The sinusoidal peaks of prescribed velocity will make the mesh to invert. To avoid, we can use some step function, which will increase velocity slowly giving time for mesh movement.
Hope this helps
I also had this same problem. I was advised to use step function. The sinusoidal peaks of prescribed velocity will make the mesh to invert. To avoid, we can use some step function, which will increase velocity slowly giving time for mesh movement.
Hope this helps