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An Experimental Investigation on the Coalescent Behaviors of Colliding Droplets

Published online by Cambridge University Press:  05 May 2011

C. H. Wang ,
K. L. Pan ,
S. Y. Fu ,
W. C. Huang  and
J. Y. Yang
C. H. Wang*
Affiliation:
Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan 10617, R.O.C.
K. L. Pan*
Affiliation:
Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan 10617, R.O.C.
S. Y. Fu*
Affiliation:
Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan 10617, R.O.C.
W. C. Huang*
Affiliation:
Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan 10617, R.O.C.
J. Y. Yang*
Affiliation:
Institute of Applied Mechanics, National Taiwan University, Taipei, Taiwan 10617, R.O.C.
*
*Professor
*Professor
**Graduate student
**Graduate student
*Professor
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Abstract

The coalescent behaviors in collisions between two droplets respectively made of different alkanes, water and alkane, methanol and alkane, and ethanol and hexadecane were experimentally studied. The coalescent results between two droplets of different alkanes are qualitatively the same as that with the same material, which simply form a spherical droplet. However, it took time to have the concentration within the droplet to become uniformly distributed. The collision results of water and alkane droplets collision become slightly more complex, in most cases, the water droplet was either inserted into or adhesive to the hexadecane droplet while only insertion was observed if the target droplet was dodecane or heptane. The inserted water droplet tends to partially expose to the environment as the volume fraction of water is sufficiently high, say, ∼0.62 for hexadecane, > 0.70 for dodecane, and > 0.78 for heptane; and the limit is lowered with the decreasing of water or merged droplet size. For the cases of methanol and alkanes, and ethanol and hexadecane, the two colliding droplets were adhesive to each other in all the studies. Furthermore, in most conditions, air bubbles were observed immediately after the collisions, while only few or even none of them might be trapped within the final merged droplet.

Keywords

Droplet collisionInsertive coalescenceAdhesive coalescence.
Type
Articles
Information
Journal of Mechanics , Volume 23 , Issue 4 , December 2007 , pp. 415 - 422
Copyright
Copyright © The Society of Theoretical and Applied Mechanics, R.O.C. 2007

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