For The Linearized Potential Flow, Frequency Domain Interface and The Linearized Potential Flow, Transient Interface, use the Interior Sound Hard Boundary (Wall) condition to model interior rigid boundary surfaces, or walls. It prescribes a vanishing normal component of the particle velocity at the boundary. Multiplied by the density, it can equivalently be expressed as a no-flow condition:

The up/down refers to the up and down side of an interior boundary. The sound-hard boundary condition is available for all analysis types. The equation above applies to the time domain calculations in the Linearized Potential Flow, Transient interface; to obtain the corresponding condition for the frequency domain, simply replace ∂/∂t with iω.