Use the Normal Velocity node in time-harmonic analysis to specify the velocity component normal to the boundary:

Here vn denotes the outward normal velocity at the boundary surface, which is specified in the vn text field. The formulation is a variant of the Ingard-Myers type impedance condition as vn = p/Zi (see Impedance, Interior Impedance, and Pair Impedance).

Enter a Normal velocity vn (SI unit: m/s).