[Simbelmynë]

Hi,

Assuming we have two incompressible fluids where a mass transfer is happening between the phases. How can this be implemented with the VOF model in a mass conservative way?

A simple example: Assume that we have 50% oxygen and 50% water in a computational cell. Lets assume that all oxygen dissolves into the water, much faster than the computational time-step.

As the VOF is formulated we still have essentially the same mixture density before and after the mass transfer.

If water is the primary phase then:
The oxygen volume fraction goes to zero, which in turn leads to the water volume fraction going to one.

If oxygen is the primary phase then:
The oxygen mass transfer to the water leads to a negligible increase in water volume fraction, which in turn leads to no change in the oxygen volume fraction.

So the questions are:
1. Is it impossible to conserve mass during mass transfer under the above conditions?
2. To minimize the error, we should use the light phase as the primary phase?


Cheers!