I haven't tried the Free Surface effect in Modal Acoustics.
I suggest you begin with the simple approach to learn Fluent. You will want to use a VOF model.
If you have questions about that, open a New Discussion in the Fluids category.
Below is a list of tutorials to help you get started with a Fluent VOF model.
https://www.google.com/search?q=fluent+vof+tutorial
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