The entrainment of air by water jet impinging on a free surface

Abstract

High-speed cine and video photographs were used to capture the flow patterns of a column of water jet impinging into a pool of water. The impact results in air entrainment into water in a form of a void and there are no mixing between the water in the jet and the surrounding water. Conservation of fluid momentum shows that the rate of increase of the height of the air void depends on the drag coefficient of the jet front. By neglecting the frictional losses, the application of energy conservation yields an expression that relates the maximum height of the air void with the properties of the water jet.3

The impact of a translating plunging jet on a pool of the same liquid

“…The results lead to a volume of entrained air proportional to F r 1/3 . Later work by Soh, Khoo & Yuen (2005) provided an integral analysis of the impact, predicting that the maximum depth of the cavity varies as F r 1/3 to leading order, in agreement with the prior work. It should be mentioned that the dynamics of these cavities are similar to the dynamics of cavities created by the impact of solid objects on liquid-free surfaces, see, for example the recent article on cavities created by the impact of circular discs in Bergmann et al (2009).…”

Large eddy simulation of rough and smooth liquid plunging jet processes

“…The highly disturbed jet evolves with a rough surface that is visibly wavy and occasionally sinuous. Due to the effect of surface tension, however, the highly disturbed jet still possesses an almost spherical bulbous tip similar to the weakly disturbed jet and to the one observed by Soh et al (2005). This shape serves as the initial disturbance that will initiate the creation of the air cavity in a similar fashion to the experiments of Zhu et al (2000) and Kersten et al (2003).…”

“…Most of the initial work on plunging jets in the continuous entrainment regime, as documented in Cummings and Chanson (1997a and b), Evans et al (1996), McKeogh and Ervine (1981), Schmidtke et al (2009), Sene (1988) and Van de Sande and Smith (1976), was experimental and semiempirical in nature, aimed at understanding the conditions of inception, the various mechanisms of air entrainment and the development of correlations to predict the penetration depth of the bubbly plume and the rate of gas entrainment. Works aimed at understanding the topological development of the flow during the initial phase of impacting jets by way of air cavity sizes, shapes, air entrainment rates and their scaling laws include notably those of Oguz et al (1995), Ohl et al (2000), Soh et al (2005) and Zhu et al (2000). Subsequent to the initial phase of impact, Kiger and Duncan (2012) and McKeogh and Ervine (1981), in their reviews, discuss two main air entrainment mechanisms-(i) air entrainment for weakly disturbed plunging jets characterized by a smooth surface and (ii) air entrainment for highly disturbed jets where the jet stream is non-uniform and its surface possesses regular or irregular ripples of varying sizes depending on the jet developing length.…”

Experimental study of multiphase flow in a model gearbox

“…With increased jet momentum, the void grows in size until it becomes unstable and collapses, and the mixing of the two fluids occurs with the formation of bubbles in the oil. The physical mechanism of air entrainment by a liquid jet is described in detail by Soh et al [12].…”