The Interior Normal Displacement node adds a normal displacement on an interior boundary and ensures that the pressure is noncontinuous here. Add this node from the Interior Conditions submenu. The pressure has a so-called slit condition on this boundary. The condition is very similar to the Interior Normal Acceleration condition having the acceleration given by the double time derivative of the displacement.

Select a Type: Displacement (the default) or Inward displacement.

For Inward displacement enter the value of the Inward displacement dn (SI unit: m/s2) in the normal direction. Use a positive value for inward displacement or a negative value for outward displacement. The normal of the boundary points outward. The normal is depicted as a red arrow in the graphics window on the selected boundary.