Entrainment characteristics of a swirling plunging jet

When a high velocity jet impinges on the free surface of receiving pool, air pocket or cavity is created on the free surface which becomes highly unstable because of the continuously impinging jet. This phenomenon is encountered widely in industrial applications such as the pouring of molten metals and plastics, stirring of chemicals and also  in nature, such as breaking waves and cascades. In the present investigation, we explored the entrainment characteristics of a swirling liquid jet plunging into a quiescent liquid pool. The results indicate that, larger amount of air is being dragged inside the liquid pool with the swirling liquid jet upto a critical swirl number beyond which the amount of entrained air decreases. Furthermore, the volume of air being entrained depends upon the trade-off between competing axial and radial momentum along with the force of buoyancy. Moreover, we observed a modified form of the Kelvin-Helmholtz instabilities which is triggerred inside the liquid pool. We also explored the breakup morphology of the initial air-cavity developed at the free surface of the receiving pool which pinches-off into smaller air pockets and air bubbles. We have also compared the entrainment characteristics of the swirling liquid jet with their non-rotating counterpart.