The Interior Normal Acceleration node adds a normal acceleration on an interior boundary and ensures that the pressure is noncontinuous. Add this node from the
Interior Conditions submenu. The pressure has a so-called slit condition on this boundary. This boundary condition can be used to model sources as, for example, the movement of a speaker cone modeled as a boundary. The condition adds the normal part of an acceleration
a0:
Alternatively, specify the inward acceleration an. The normal of the boundary is interpreted as pointing outward.