Prescribed Velocity
The Prescribed Velocity node adds a boundary or domain condition where the velocity is prescribed in one or more directions. This condition is applicable for time- dependent and frequency domain studies. It is possible to prescribe a velocity in one direction, leaving the structure free in the other directions. The Prescribed Velocity node is a constraint and overrides any other constraint on the same selection.
To prescribe velocities on the top or bottom surfaces of the shell, use Prescribed Velocity, Interface.
Shell Properties
The selection in this section only acts as a filter for the boundary selection.The condition is applied all through the thickness of the shell.
If the same layer is selected in two Prescribed Velocity nodes being active on the same boundary, the second definition will override the previous.
All other settings for the Prescribed Velocity node are described in the documentation for Prescribed Velocity in the Solid Mechanics interface.
Location in User Interface
Context Menus
Ribbon
Physics tab with  Layered Shell selected: