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Acoustics Multiphysics - Disk (with hole in centre) backed by air-filled cylinder

Posted May 10, 2011, 11:07 a.m. EDT Acoustics & Vibrations, Structural Mechanics Version 3.5a 3 Replies

David Mackie
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Hi,

I'm trying to compute the eigenmodes for a structure very similar to that in the example model - 'Vibrations of a Disk Backed by an Air-Filled Cylinder' however the only difference between my model and the example one (neglecting differences in dimensions - smaller radius, height and plate thickness) is that my steel disk fixed to the top of the cylinder has a hole cut in the centre. Having followed the example model I get error:6262 -

Extrusion coupling operator interpolation failed for at least one point: no source point found
- Geometry: 2
- Boundaries: 4,8
- Destination coordinates: [-0.0002940993961094952; -2.132711293129105e-005], [-0.0003489856614847664; -8.797555405163659e-005], [-0.0002767848858056061; -8.594269809094498e-005], [-0.0003268898554664816; -0.0001572383083902501], [-0.0002220060410955322; -1.762947569705455e-005], ...
Failed to evaluate variable Jacobian.
- Variable: wtt

I suspect it has something to do with the boundary coupling between the cylinder of air and the central hole part of the disk.
I'm wondering if anyone has a solution to this or perhaps an alternatrive technique to the one I've used so far (multiphysics model with the disk with central hole as a 2D mindlin plate eigenfreq analysis and the cylinder as a 3d pressure acoustics eigenfreq analysis).

Thank you in advance

David
3 Replies Last Post May 17, 2011, 8:01 p.m. EDT
Mihir Shetye
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Posted: 1 decade ago May 10, 2011, 9:26 p.m. EDT
Hi David,

I do not have the structural mechanics module hence cannot open the model. But since the error is in evaluating the acceleration, a guess would be the boundary condition inside the opening. Have you modeled an air region in the hole? If so, double check and make sure that the boundary conditions have been properly applied in the pressure acoustics domain.

Mihir
Hi David, I do not have the structural mechanics module hence cannot open the model. But since the error is in evaluating the acceleration, a guess would be the boundary condition inside the opening. Have you modeled an air region in the hole? If so, double check and make sure that the boundary conditions have been properly applied in the pressure acoustics domain. Mihir
David Mackie
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Posted: 1 decade ago May 12, 2011, 5:14 a.m. EDT
Hi Mihir,

Thank you for your reply. At the moment the disk is a 2D mindlin plate and the central hole is just a 'void' cut in the middle so I think there's probably a better way of doing this or a specific way of modelling the air region in the hole?

Kind regards

David
Hi Mihir, Thank you for your reply. At the moment the disk is a 2D mindlin plate and the central hole is just a 'void' cut in the middle so I think there's probably a better way of doing this or a specific way of modelling the air region in the hole? Kind regards David
Mihir Shetye
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Posted: 1 decade ago May 17, 2011, 8:01 p.m. EDT
Hi David,

Sorry missed the part about the 2D plate. I am not too familiar with the plate formulation hence cannot comment on that. However, the error does seem to be in a boundary condition. In the pressure acoustics domain, do you have separate boundaries on the top of the cylinder so that there is no acceleration condition on the part that is supposed to be open (due to the void)? If there is a single boundary there, then that might be the cause of the error. I am only guessing at this point since I do not have the module to evaluate myself. Anyway, another suggestion is to maybe try 2d axi-symmetry so that the air region can be modeled.

Mihir
Hi David, Sorry missed the part about the 2D plate. I am not too familiar with the plate formulation hence cannot comment on that. However, the error does seem to be in a boundary condition. In the pressure acoustics domain, do you have separate boundaries on the top of the cylinder so that there is no acceleration condition on the part that is supposed to be open (due to the void)? If there is a single boundary there, then that might be the cause of the error. I am only guessing at this point since I do not have the module to evaluate myself. Anyway, another suggestion is to maybe try 2d axi-symmetry so that the air region can be modeled. Mihir

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