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Mingjun Pang 1 and Jinjia Wei 2
Academic Editor:Yong Chen
1, School of Mechanical Engineering, Changzhou University, Changzhou 213016, China
2, State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China
Received 18 February 2014; Revised 14 May 2014; Accepted 10 June 2014; 2 July 2014
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
Due to good physical properties, bubbly flows are frequently encountered in many industrial fields such as smelting of metals, two-phase heat exchanger, and drag-reduction engineering by microbubbles [1-3]. In order to understand hydrodynamic characteristics of bubbly flows, many numerical and experimental investigations have been carried out in the past 30 years [1-21]. As pointed out by some researchers [4-6], of many hydrodynamic properties of the bubbly flow, it is very important for the system design of the drag reduction by microbubbles to deeply understand the liquid-phase turbulence modulation by microbubbles. In order to understand the turbulence modulation mechanism by bubbles, many experimental and numerical investigations had also been performed for different kinds of turbulence. A detailed review on the liquid turbulence modulation by bubbles can be referred to [7]. A review on physical phenomena of bubbly flows had been presented in [8]. Ceccio [9] presented a detailed review on the drag reduction mechanism by microbubbles. Thus, the related content cannot be repeated again here.
As a matter of fact, the mechanism on the liquid turbulence modulation by bubbles cannot be fully understood yet and the existing mechanisms cannot be generally accepted so far. From the above review, one can see that the present literature only showed a modulation trend on the liquid-phase turbulence by bubbles and did not analyze why the liquid turbulence is enhanced or damped by bubbles. That means that the modulation mechanism of the liquid-phase turbulence by bubbles is not essentially clear. In order to bring an effective control of bubbly flows into effect in industrial processes, it is very important to deeply understand interactions between the bubble and liquid phases. In view of the previous reason, a mechanism of the liquid-phase turbulence...