Non-dimensional numbers in multiphase flows
 

Two phases (air and water) are flowing simultaneously through a rectangular channel as shown in Figure. If the velocity of air is increased by 2, 4 and 8 times that of the liquid inlet velocity in three different cases. The dynamics of the interface will be different for these three different velocities of the gas phase due to the momentum transfer from the gas phase to the liquid phase. But if we calculate the ratios of inertial forces of the gas phase to that of the liquid phase or the different non-dimensional numbers for both gas and liquid phases e.g., weber number. We are getting an understanding that the liquid phase inertia dominates and also the magnitude of numbers shows that the effect of gas phase inertia on the interface dynamics is secondary, due to the high density and viscosity of the liquid phase. But visually I am seeing the significant contribution of gas phase inertia on the interface dynamics.

https://drive.google.com/file/d/1LQq...ew?usp=sharing

Therefore, my questions are:
1. How to explain the contribution of gas phase inertia through non-
dimensional numbers for the above problem?
2. If not non-dimensional numbers, then what could be the best way to quantify the effect of gas phase inertia on the interface dynamics?