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how to get rid of unrealistic offset in simulation

Posted Jun 22, 2015, 1:11 p.m. EDT Acoustics & Vibrations Version 4.3 1 Reply

Daniel Atehortua
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Hi everyone,

I am performing transient acoustic simulation runs in solid media (the sketch of the geometry is attached to this message) in order to assess sound wave interaction with different type of defects. To do so, I am integrating the sound pressure of the incident wave along a specific line (i. e. an edge) in every time step. The results looks like the "figure" archive attached to this message. The problem is that I am getting a strange offset value, which seems to be present any time the wave is reflected by a defect surface (in fact, it is a line as the simulation is 2D). I am sure the offset does not depend on mesh quality (I have tested several meshes).

Another thing that could be producing the offset might be related with convergence issues at some specific time steps. When the convergence is not good enough, the time dependent solver seems to jump, and I guess it could be producing the unwanted behaviour too.

Could you please tell me some ideas in order to get rid of it?? I will be really thankful.

Best Regards,

Dan

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1 Reply Last Post Jul 29, 2015, 10:34 a.m. EDT
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Daniel Atehortua
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Posted: 9 years ago Jul 29, 2015, 10:34 a.m. EDT
Ok, I think I found the problem, if somebody else is interested on it.

By tightening up relative and absolute error (up to 1e-8), I have been able to reduce y-offset from 20 Vpp to around 1 Vpp. Of course, this is very time consuming and demands extremely high computational resources. Now, in order to reduce computational time, I have found that some boundary conditions require more computational effort, so I changed them and the computed time was significantly reduced. This is where one needs to be creative in order to keep model characteristics when doing those changes. Now my model runs like a charm!!!!

Best Regards,

Dan
Ok, I think I found the problem, if somebody else is interested on it. By tightening up relative and absolute error (up to 1e-8), I have been able to reduce y-offset from 20 Vpp to around 1 Vpp. Of course, this is very time consuming and demands extremely high computational resources. Now, in order to reduce computational time, I have found that some boundary conditions require more computational effort, so I changed them and the computed time was significantly reduced. This is where one needs to be creative in order to keep model characteristics when doing those changes. Now my model runs like a charm!!!! Best Regards, Dan

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