Prescribed Normal Mesh Velocity
Use the Prescribed Normal Mesh Velocity node to specify the normal velocity of the boundary. The node can be used on the boundary of domains with free displacement. No constraints are set on the tangential velocity.
Simulations using moving meshes, with a boundary moving in the normal direction, can sometimes need a stabilizing term to suppress the formation of local boundary segments of high curvature. This can be of particular importance in an automatic remeshing sequence, where the remeshing step might amplify local curvature artifacts.
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 the mean surface curvature (SI unit: 1/m), defined as:
where ∇T is the surface gradient operator.
Normal Mesh Velocity
Enter a value or expression for the Normal mesh velocity vn (SI unit: m/s).
Moving Boundary Smoothing
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.
As the local mesh element size h at a boundary is included in the expression for vmbs, a large value for δmbs can result in an uneven velocity of mesh movement along a boundary. For this reason, it is recommended to use the smallest δmbs needed to achieve a stable solution.