Erik Kostson
Ansys Employee

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