Using the Interface Momentum Dissipation Model

The Interface Momentum Dissipation model adds extra momentum dissipation in the proximity of the free surface to dissipate parasitic currents. The momentum dissipation is proportional to the velocity gradients and the interface artificial viscosity.

Parasitic currents are caused by discretization errors that arise due to solution discontinuities across the free-surface interface. An interface between phases represents a discontinuity in the solution domain. At this interface, all material properties, (for example, density, viscosity, and thermal conductivity) are discontinuous. All gradients of dependent variables, (for example, gradients of velocity, pressure, and temperature), are also discontinuous. In the case of flows that are dominated by surface tension, pressure, too, is discontinuous across the interface.

Discontinuities in solution fields can cause discretization errors which do not scale with the mesh size. In the case of free-surface flows, these errors can cause some spurious or parasitic currents. In many cases these currents are negligible relative to the other transport processes that are present and they do not affect the solution. However, as the parasitic currents can affect the solution in some cases, the Interface Momentum Dissipation model can be used to reduce them.

You access the Interface Momentum Dissipation Model from the Phase Interaction Model Selection dialog for the relevant pair of phases.

The Interface Artificial Viscosity node provides a choice between constant or field function for the method that defines the artificial viscosity.

Larger values of interface artificial viscosity are better at removing parasitic currents, but they can affect the physics of the problem on a particular mesh. Ensure that you specify values of interface artificial viscosity which are sufficient to remove or reduce parasitic currents, but are not large enough to affect the quality of the results.