It seems to me like you are looking at some way of using water to dampen acoustic oscillations. I'm thinking sloshing of water causes the damping. If this is the case, you should be able to use (again I'm taking the liberty of assuming that I fully understand the physics here) the multiphase models in Fluent to estimate the sloshing. You will need to combine it somehow with acoustics. You can either use Ansys Mechanical to drive the acoustics and use system coupling with Fluent to model the sloshing. Or you can (perhaps) use the acoustic solver in-built in Fluent. I'm hesitant here because I do not completely understand the physics of what you are trying to achieve.
The best way to find out a direction would be to look at previous work done in this field using Ansys. Please look at literature and try to replicate their results. This would give you a great starting point.