

January 18, 2023 at 8:02 amDiogo MartinhoSubscriber
Hi all,
Probably not a good question but I understand the eulerian model solves a set of equations for each phase. However, when I start my simulation and check the equations I only have a continuity equation and then a vfgas equation. Is this vfgas the continuity equation for the secondary phase? 
January 18, 2023 at 9:13 amDrAmineAnsys Employee
By default only the secondary phase volume fraction transport equation will be solved. With the compatbility condition the volume fraction of the primary phase is calculated.
A bulk pressure continuity equation is always solved.

January 18, 2023 at 9:20 amDiogo MartinhoSubscriber
Hi, thanks for your quick answer.
Can you detail a bit your answer?
So, the continuity equation there (black line) is the primary phase continuity equation. And then I am solving a transport equation for the volume fraction and because of the constraint that the sum of alpha might be equal to one, I have the volume fraction of the liquid phase? 
January 18, 2023 at 10:13 amDrAmineAnsys Employee
I think I was clear as I wrote we are solving a pressure continuity equation for the bulk and not for the primary phase. The primary phase volume fraction is calculated from the 1sum_over_all_secondary_phases(volume fraction).

January 18, 2023 at 10:28 amDiogo MartinhoSubscriber
Ok, thanks.
So, let's say we are simulation wateroilhydrogen, and they are defined as three phases where, water will be the primary phase and the remaining secondary phases. Will I have a continuity equation for the oil, another for the hydrogen, a continuity equation for the pressure (I am not entirely sure if I understood this equation though) and finally, the water will be 1sumover_all_secondary_phases(volume fraction)? 
January 18, 2023 at 10:33 amDrAmineAnsys Employee
Yes. (Pressure Based Continuity Euqation: Check Solver Theory and you will perhaps understand what I am talking about).

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