Use the Mesh Slip node (

) on boundaries of deforming domains where the mesh can slip (that is, only move in the current tangential direction). The condition is equivalent to specifying a zero normal mesh velocity in a 
Prescribed Normal Mesh Velocity node.
 
    For common boundary condition settings, see Common Boundary Condition Feature Settings. The Mesh Slip condition allows the 
Nitsche method and 
Weak constraints (the default).