Use the Prescribed Normal Mesh Velocity node () to specify the velocity of the boundary in the current normal direction. The node can be used on the boundaries of deforming domains. No constraints are set on the tangential velocity.

The moving boundary smoothing option smooths the normal mesh velocity of the Prescribed Normal Mesh Velocity node according to the following equation:

where v0 is the desired normal mesh velocity, and vmbs is a smoothing velocity according to:

Here δmbs is a moving boundary smoothing tuning parameter (unitless), h is the mesh element size (SI unit: m), and H is the mean surface curvature (SI unit: 1/m), defined as:

where ∇T is the surface gradient operator.

For common boundary condition settings, see Common Boundary Condition Feature Settings. The Prescribed Mesh Velocity condition allows the Nitsche method and Weak constraints (the default).

Enter a value or expression for the Normal mesh velocity vn (SI unit: m/s).

By default, the Enable moving boundary smoothing check box is not selected. To enable boundary smoothing, click to select the check box, and then enter a value or expression for the Moving boundary smoothing tuning parameter, δmbs (unitless). The default value is 0.5.