Lift force acting on a pair of clean bubbles rising in-line

Hiroaki Kusuno,Hiroya Yamamoto,Toshiyuki Sanada

doi:10.1063/1.5100183

Abstract

In this study, we experimentally observed the motion of a pair of bubbles initially positioned in line, especially focusing on the intermediate Reynolds number case, i.e., 20 &lt; Re &lt; 60. We observed three types of motion at different Reynolds numbers. At a low Reynolds number (Re &lt; 20), the trailing bubble collided with the leading bubble like a pair of rigid spheres. At a high Reynolds number (100 &lt; Re), the trailing bubble moved out from the original vertical line joining the two bubbles. At intermediate Reynolds numbers (20 &lt; Re &lt; 60), small differences in bubble size affected the motion. When the leading bubble was larger than or equal to the trailing bubble, the trailing bubble first approached the leading bubble and later moved out from the initial vertical line owing to a lift force. When the leading bubble was smaller than the trailing bubble, the trailing bubble first approached the leading bubble, and then a repulsive force acted on both bubbles so that both of them moved out from the vertical line in opposite directions. These motions are attributed to two effects, the first is potential effects at short distance between bubbles, and the second is the wake of the leading bubble.

Highlights

Flows are widely observed in natural phenomena and utilized in various industrial processes
It is well known that there is a peak in the void fraction near the wall, for bubbly flow in a pipe, and this completely changes the turbulent structure of the flow (Serizawa et al, 1975)
We focused on the motion of a pair of clean bubbles initially positioned in line at intermediate Reynolds numbers (20 < Re < 60) which are between those investigated by Katz and Meneveau (1996) and by Kusuno and Sanada (2015)

Summary

Introduction

Flows are widely observed in natural phenomena and utilized in various industrial processes In such processes, many different phenomena for bubbly flow have been studied, such as, the bubble generation (Shen et al, 2017; Bolaños-Jiménez et al, 2016), the variation of bubble shape and the wake of the bubble (Cano-Lozano et al, 2016b; Sharaf et al, 2017; Premlata et al, 2015; and Wang and Socolofsky, 2015), the bubble coalescence and bounce (Han et al, 2016; Klaseboer et al, 2014), and the interaction between the bubble and wall (Dabiri and Bhuvankar, 2016). Bubble–bubble interaction is one of the key factors in the formation of bubble clusters

Methods

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Discussion

Conclusion