About the Volume of Fluid (VOF) Method

The volume of fluid method (VOF) is an Eulerian algorithm that predicts the location of the interface between the two fluids, also known as the "free-surface." The app solves an advection equation to track the location of the interface.

See Also
Defining the Fluid Physics of a Flow Simulation
About Physics in a Flow Simulation

In general, the VOF method is used to predict the flow between immiscible fluids. Some typical industry applications include:

  • Simulation of multi-phase flows where bubble formation is important in jet break up and bubble formation due to cavitation, such as propeller damage in marine applications.
  • Simulations where the effect of gravity and other forces affect the free surface, such as in atmospheric and oceanic simulations, tank sloshing prediction, and dam break simulations.
  • Capillary flows where the effects of surface tension and wall adhesion are important.

You can solve using the VOF method if your simulation includes a VOF section in which all fluids are incompressible or if one of the fluids is a compressible ideal gas. If one of the fluids is compressible, you should use the VOF method only for flows with a low Mach number. In addition, the VOF method uses the segregated solver; you cannot use the VOF method with the coupled solver.

When you use the VOF method, you should also perform the following configurations to the transient step parameters:

  • Enable automatic time incrementation for the step, and specify a CFL number of 0.5. These two settings reduce the diffusion errors in the predicted multi-phase interface.
  • Set the under-relaxation factors to 1 in all the transport equations involved in the simulation (for example, pressure, momentum, energy, and turbulence).