Learning Forum

[sadrip]

Hello,

I have been trying to get to see the effect of damping of water on the deformation of a polymer disc I simulate in Ansys Harmonic Acoustics. However, Ansys does not seem to be taking it into account. One side of the polymer disc is set to be fixed, and the top surface and side walls of it are under a pressure source of 1Pa amplitude. Here are screenshots of the structure and the deformation spectrum I get for such structure, where I have plotted the deformation of center point on top surface of the polymer disc:

[Erik Kostson]

Hi

Yes so it is possible, and as I posted before I did a small benchmark before as shown in this post:
The same benchmark as above but in harmonic acoustic where we expect a pressure 1 m away from the excitation (100 Pa excitation, alpha=1, attenuation coef. => 321 viscosity) of 100 Pa/(exp(1 m)) =36.7 Pa, and that is what we get in the analysis as shown below.


All the best

Erik

[sadrip]

Dear
Thank you for sharing your opinion and the example. I understand that the effect of viscosity can be seen in your example, where only an acoustic region is defined. But is there a chance that when I defined a structural region (the polymer disc) and an acoustic region (water), I should have additional settings (in addition to setting an FSI boundary between the two), in order to see the effect of water viscosity on the vibration of the top surface of the polymer disc?
I'm also having a suspicion that the meshing of my structure not being accurate might be causing it. Based on your experience, do you think this could be the case? (I have explained my meshing issue in this post: /forum/discussion/comment/125425#Comment_125425)
I would appreciate it if you could share your opinion.

Thank you Parinaz

[Erik Kostson]

HI

Yes, that is correct, the example is to see attenuation in acoustic wave propagating (acoustic media).

What you are after is the fluid added mass and added damping effect so called - so from the fluid on to the disc, influencing the freq. of the disc and amplitude of vibration.

We can capture the fluid added mass (so water will lower freq. of a structure that is submerged), but we can not capture the fluid added damping effect (say harmonic acoustics)., hence viscosity will not do anything in this situation (so when we look on the added damping from the fluid).

So to close this discussion, the answer to your question('in order to see the effect of water viscosity on the vibration of the top surface of the polymer disc?') is:

We can not model and capture that effect (water viscosity/added damping effect on the vibration of the structure).

All the best

Erik

[sadrip]

Dear Thank you so much for explaining. It makes sense now. Only one last question, what is your suggestion if we want to have the effect of water viscous damping on the vibration amplitude of the disc? Now you say that Harmonic Acoustics cannot model that, what other module in Ansys you would suggest for that?
I would appreciate your comment on this.
Thank you Parinaz

[Erik Kostson]

I am afraid that I do not have an answer to your 2 questions or any suggestions.

All the best and take care.

Erik