You must use the pressure-based solver. The VOF model is not available with the density-based solver.

All control volumes must be filled with either a single fluid phase or a combination of phases. The VOF model does not allow for void regions where no fluid of any type is present.

Streamwise periodic flow with specified mass flow rate cannot be modeled when the VOF model is used.

The second-order implicit time-stepping formulation cannot be used with the VOF explicit scheme.

When tracking particles with the DPM model in combination with the VOF model, the Shared Memory method cannot be selected (Parallel Processing for the Discrete Phase Model). (Note that using the Message Passing or Hybrid method enables the compatibility of all multiphase flow models with the DPM model.)

The VOF model is not compatible with non-premixed, partially premixed, and premixed combustion models.