Interior Normal Velocity
The Interior Normal Velocity node adds the boundary condition for a moving interior boundary. Add this node from the Interior Conditions submenu. This can, for example, represent a thin vibrating structure or s speaker membrane. The condition reads
The condition ensures that the normal velocity is defined on both the up and down side of the boundary, while applying a slit on the pressure (the pressure is discontinuous across the boundary).
Normal Velocity
Select the Type: Velocity (default) or Normal velocity and specify either the Velocity (vector) vb(t) or the normal component through the Normal velocity vn(t).