Use the Sound Hard Boundary (Wall) condition to model 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 sound-hard boundary condition is available for all study types. The equation above applies to the time-domain calculations in The Linearized Potential Flow, Transient Interface; to obtain the corresponding condition for frequency domain, simply replace ∂/∂t by iω.

In The Linearized Potential Flow, Boundary Mode Interface the no-flow or wall condition, known as sound hard, sets the normal acceleration — and thus also the normal velocity — to zero at the edge.