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Help me: Optimization the pressure!!

Posted Nov 13, 2012, 9:27 p.m. EST Acoustics & Vibrations Version 4.3 3 Replies

Tran Quang Dat
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Greetings,

Thanks for reading my problem.
I have some problem about setting the optimization module.
My model is simple, In Acoustic Physic, I use an acoustic lens to converge the pressure at the focal point (You can see the attached file). I want to find the optimal value of the lens radius (R1, R2) to maximize the pressure at the focal point. So I use the optimization module (including Optimization and Deformed Geometry).
I set up the valuables R1 and R2 in these equations (which represents the shape of the acoustic lens):
y=sqrt(R1^2-(x+a1)^2)+b1
y=sqrt(R2^2-(x+a2)^2)+b2
in order to minimize the following equation:

(p-150)^2
Where p is the pressure at the focal point and 150 is a reference pressure, both applied to domain.
The algorithm to optimize in comsol as follows:

1) Assign a value to R1, R2
2) Estimate the value of pressure at the focal point
3) Verify if optimality condition is satisfied, otherwise start again from 1
But I always got the error as follows:
Warning: Inverted mesh element near coordinates (0, 0.05996).
Warning: Inverted mesh element near coordinates (0, 0.023996).

Does anyone has any ideas about this weird warning?

Thanks in advance,

Tran Quang Dat

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3 Replies Last Post Nov 14, 2012, 2:37 a.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Nov 14, 2012, 1:29 a.m. EST
Hi

I do not have the acoustic module, but the error you get means that the dimensions of your geometry has changed so much that your mesh is getting very poor (or that you initial mesh is too poor (which could be too coarse but not necessarily). Try turning on the "plot while solving" to see how you geometry is changed. Another way could be to give some min max limits to your variables. Perhaps COMSOL is finding a solution that does not allow for a "physical" solution

--
Good luck
Ivar
Hi I do not have the acoustic module, but the error you get means that the dimensions of your geometry has changed so much that your mesh is getting very poor (or that you initial mesh is too poor (which could be too coarse but not necessarily). Try turning on the "plot while solving" to see how you geometry is changed. Another way could be to give some min max limits to your variables. Perhaps COMSOL is finding a solution that does not allow for a "physical" solution -- Good luck Ivar
Tran Quang Dat
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Posted: 1 decade ago Nov 14, 2012, 1:55 a.m. EST

Hi

I do not have the acoustic module, but the error you get means that the dimensions of your geometry has changed so much that your mesh is getting very poor (or that you initial mesh is too poor (which could be too coarse but not necessarily). Try turning on the "plot while solving" to see how you geometry is changed. Another way could be to give some min max limits to your variables. Perhaps COMSOL is finding a solution that does not allow for a "physical" solution

--
Good luck
Ivar


Thank You very much for Your quickly response.

Could you please guide me how to use "plot while solving" in Comsol.
I gave some min max limits for variables and mesh is enough for my model.

Best Regards,

Tran Quang Dat
[QUOTE] Hi I do not have the acoustic module, but the error you get means that the dimensions of your geometry has changed so much that your mesh is getting very poor (or that you initial mesh is too poor (which could be too coarse but not necessarily). Try turning on the "plot while solving" to see how you geometry is changed. Another way could be to give some min max limits to your variables. Perhaps COMSOL is finding a solution that does not allow for a "physical" solution -- Good luck Ivar [/QUOTE] Thank You very much for Your quickly response. Could you please guide me how to use "plot while solving" in Comsol. I gave some min max limits for variables and mesh is enough for my model. Best Regards, Tran Quang Dat
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Nov 14, 2012, 2:37 a.m. EST
Hi

the best is to use the help and the search properties ;)

under the Solver nodes you have a (closed by default) tab stating "Results wile solving", there under you can define which plot to show and how often (each step taken by solver) this allows you to follow what is going on, and often helps to identify problems (wrong settings)

There is also the "Definition - Probes" that are also often useful

--
Good luck
Ivar
Hi the best is to use the help and the search properties ;) under the Solver nodes you have a (closed by default) tab stating "Results wile solving", there under you can define which plot to show and how often (each step taken by solver) this allows you to follow what is going on, and often helps to identify problems (wrong settings) There is also the "Definition - Probes" that are also often useful -- Good luck Ivar

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