Computational fluid dynamics modelling of air entrainment for a plunging jet

This study focuses on computational fluid dynamics (CFD) modelling of the air entrainment phenomena in water columns which are commonly used in processing plants. The CFD model is first validated against experimental data. Then, a comprehensive set of CFD simulations are conducted to understand the effect of inlet jet velocity, nozzle diameter, tank diameter, and tank height on the bubble formation. Three main patterns are identified: dispersed bubbles, medium air pockets (MAP) and large air pockets (LAP). For the dispersed bubble case, the initially formed air pockets break into smaller bubbles and hence the water level rises linearly. For the MAP case, the size of the air pockets remains larger than for the dispersed bubble case, though, with time they burst at the surface. Finally, for the LAP case, the inkling jet interacts violently with the wall and hence large air pockets are trapped within the column, causing the overflow of the fluid. The flows are further analysed using non-dimensionless Reynolds and Froude numbers, providing an acceptable range of operating parameters that ensure the fluid does not overflow.