GAS ENTRAINMENT BY PLUNGING LIQUID JETS.

Abstract

The mechanism of gas entrainment by plunging liquid jets depends upon the jet velocity, liquid physical properties (mainly viscosity) and geometric parameters such as jet length and nozzle design, also on the turbulence level in the jet. For viscous laminar jets gas is entrained in the form of a thin gaseous film which breaks up into bubbles. For low-viscosity jets the mechanism of entrainment is related to the jet surface instability and the interaction of disturbances on the jet surface with the receiving pool liquid. For high-velocity jets gas friction forces are important since they affect the jet surface. Gas is captured by the jet roughness and in the gas boundary layer developed along the jet. The conditions which yield the onset of gas entrainment are discussed. It is demonstrated that the relationships for the onset of entrainment are different for laminar and for turbulent liquid jets, in accordance with different mechanisms which lead to the entrainment. For low-viscosity liquid jets two regions of the onset of entrainment can be observed, namely, droplet and continuous-jet regions. 92 Refs.