You can use flow out bounduary in euler silber.

Solver

Impedance is for lagrange partid.

https://www.grc.nasa.gov/www/k-12/airplane/reflects.html

Thank you.

I know flow out boundary works for eulerian models. But I'm working on Lagrangian models.

Impedance boundary just works for normal component of waves. But still tangent component of wave reflect.

you thing is it possible to model a material around geometry boundaries to decrease reflected wave?

transmit bonduary

You need to extend the calculation domain w an increasing aspect ratio. I guess this is the part of CFD that is belonging to art