[multiphaseEulerFoam void fraction calculation]
 

hello, i am beginner of OpenFOAM

when i used the multiphaseEulerFoam slover which can calculate the multi compressive fluids including heat transfer, i had one question.

when i simulated the air injection into the water (research topic : assessment of two phase circulation enhanced by air injection), the alpha values of air (ex) alpha.air), in other words, the void fraction of air seems underestimated.

when i compared the OpenFOAM results with experiment results which were conducted in our laboratory, the void fraction of air is so much underestimated.

for example, at the 1lpm air injection rate case, the experiment shows the average void fraction of air in the water is 10%, however, in my OpenFOAM case, the average void fraction of air in water is less than 1%..

but, when i compared the velocity of water enhanced by driving force which came from air bubbles, the velocity values between openfoam and experiment are similar with each other (of course, the water velocity calculated by openfoam is also underestimated compared with experimental values)

so is there anyone who knows the reason why the void fraction of air is underestimated in multiphaseEulerFoam of OpenFOAM?

thank you for reading my post!

Need more details
 

Can you share the case?
How you modeled the sparger and flow rate in your simulation?

Drag will also affect your alpha.air.
It is laminar simulation?

Share the case settings.

Thank you for your reply.

The case is that the air bubbles were injected from inlets in the reactor system to remove contaminated particle. Actually, in the case, the role of air bubbles which were injected into the water that is working fluid of the reactor is not only removing the contaminated particle in the reactor but also enhancing the circulation performance of working fluid.
(as giving water the driving force caused by buoyancy force of air bubbles)


So in the cases, i wanted to see how the effect of air bubbles in terms of improving the circulation of working fluid is. thus i conducted the simulation by using openfoam.

To achieve the purpose of my research,
i set the solver as the multiphaseEulerFoam which can calculate multi phase flow including heat transfer (because, for the future work, i will include the heat transfer in the air injection case)

in the case, there are nine spargers (=inlets) which inject the air bubbles
And the boundary condition of U.Air was set as fixed values (=0.1m/s, 0.2m/s etc..)

And i set the momentum transfer model as laminar (actually, i think that the case may be turbulent based on Reynolds number, however, when i used the turbulence model instead of laminar model, the water velocity was so much underestimated.. actually this is one of another questions(problems)..)

And drag force was set as default of multiphaseEulerFoam solver
-->air in water (=bubbles) : SchillerNaumann (swarmCorrection X)
-->water in air (=droplet) : SchillerNaumann (swarmCorrection X)
--> air and water : segregated (no distinct boundary between air and water)


As i think, the one of reasons why there is underestimation of void fraction is due to the blending model

Can blending model be one of reason to underestimation of void fraction?

thank you very much!