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Mingjun Pang 1,2 and Jinjia Wei 1 and Bo Yu 3
Recommended by Tomoaki Kunugi
1, State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China
2, School of Mechanical Engineering, Changzhou University, Changzhou 213016, China
3, Beijing Key Laboratory of Urban Oil and Gas Distribution Technology, China University of Petroleum, Beijing 102249, China
Received 3 November 2012; Revised 31 December 2012; Accepted 7 January 2013
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
1. Introduction
Bubbly flows exist extensively in industrial processes such as two-phase heat exchangers, bubble column reactors, smelting of metals, aeration and stirring of reactors, air-conditioning engineering, wastewater treatment, fermentation reactions, mineral floatation, cavitating flows, and transportation lines, [ 1- 3]. The above applications have stimulated many researches on bubbly flows and have demanded a deep understanding of bubbly hydrodynamics. Therefore, the bubbly flow has received much attention in the academic world over the past 30 years. Of numerous study contents on the bubbly flow, it is very important to accurately and quantitatively understand the turbulence modulation by bubbles, because it controls directly heat transfer and mixing efficiency of bubbly flows and the drag reduction rate by bubbles.
Currently, some researchers had performed definite studies on the turbulence modulation by bubbles and had obtained some important conclusions. Serizawa and Kataoka summarized three kinds of turbulence suppression mechanisms [ 4]. Kato et al. deduced that the bubble influencing the liquid turbulence is just like the influence of the solid particle on the gas turbulence: large bubbles enhance the liquid-phase turbulence, whereas small bubbles reduce the liquid turbulence [ 5]. This view is also accepted by Kim et al. [ 6], and they pointed out that when there is no change in volume of the dispersed phase, the turbulence production and dissipation can be understood by similar mechanisms. So et al. [ 7] and Molin et al. [ 8] considered that the lift force direction and magnitude are sensitive to the bubble size, so it is possible that the reason for the suppressed velocity fluctuations is the modification of the...