Question: ANSYS Fluent offers two different approaches to describe the volume fraction (vof) transport equation for multiphase models: implicit and explicit. When considering mass transfer, is there a difference with respect to accuracy for these two formulations? Solution: Yes, using default settings there can be a difference if the mass transfer depends on solution variables (e.g. concentration). By default, Fluent solves the vof transport equation only once at the beginning of a time step for the explicit formulation. For the implicit formulation vof is solved every iteration. You can force that Fluent solves vof every iteration for the explicit formulation from the multiphase panel > expert. Then the results of both formulations should be identical, given a sufficiently small time step size and a well converged solution within each time step. Please refer to the attached document for additional details.

Attachments:
1. 2046040.pdf