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Dynamics of internal jets in the merging of two droplets of unequal sizes

Published online by Cambridge University Press:  19 April 2016

Chenglong Tang ,
Jiaquan Zhao ,
Peng Zhang ,
Chung K. Law  and
Zuohua Huang
Chenglong Tang
Affiliation:
Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA State Key Laboratory of Multiphase Flow and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, PR China
Jiaquan Zhao
Affiliation:
Department of Mechanical Engineering, Hong Kong Polytechnic University, Hong Kong, PR China
Peng Zhang*
Affiliation:
Department of Mechanical Engineering, Hong Kong Polytechnic University, Hong Kong, PR China
Chung K. Law*
Affiliation:
Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA Center for Combustion Energy, Tsinghua University, Beijing 100084, PR China
Zuohua Huang
Affiliation:
State Key Laboratory of Multiphase Flow and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, PR China
*
†Email addresses for correspondence: [email protected], [email protected]
†Email addresses for correspondence: [email protected], [email protected]
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Abstract

The head-on collision, merging and internal mixing dynamics of two unequal-sized droplets were experimentally studied and interpreted, using water, $n$-decane and $n$-tetradecane to identify the distinguishing effects of surface tension and liquid viscosity on the merging and mixing patterns. It is shown that, upon merging of water and $n$-decane droplets, mushroom-like jets of dissimilar characteristics develop within the merged mass for small and large values of the impact Weber number (We), and that such jets are not developed for intermediate values of We. Furthermore, such jet-like mixing patterns were not observed for droplets of $n$-tetradecane, which has smaller surface tension and larger viscosity as compared to water. A regime nomogram relating the Ohnesorge and symmetric Weber numbers is constructed, providing a unified interpretation of the internal mixing patterns. Numerical simulations based on an improved volume-of-fluid method and an adaptive mesh refinement algorithm provide auxiliary diagnoses of the flow fields and the observed phenomena.

JFM classification

Drops and Bubbles: Breakup/coalescence Drops and Bubbles: Drops Drops and Bubbles: Drops and Bubbles
Type
Papers
Information
Journal of Fluid Mechanics , Volume 795 , 25 May 2016 , pp. 671 - 689
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Copyright
© 2016 Cambridge University Press 

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Footnotes

‡

The first and second authors contributed equally to this work.

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