Formation and breakup of compound pendant drops at the tip of a capillary and its effect on upstream velocity fluctuations
Author
Che, Zhizhao
Wong, Teck Neng
Nguyen, Nam-Trung
Chai, J. C.
Date of Issue
2011School
School of Mechanical and Aerospace Engineering
Abstract
In this paper, the formation and breakup process of compound pendant drops (CPDs, pendant drops with
smaller drops or bubbles in them) at the tip of a glass capillary and its effect on upstream velocity fluctuation
are experimentally investigated. The formation process of an air/water compound drop from a
CPD consists of four main stages. First, an air plug in the capillary flows into the small liquid pendant drop
to initialize a small CPD. Next, a liquid slug flows into the CPD, and the liquid in the CPD accumulates.
Subsequently, an air plug flows into the CPD, and it coalesces with the existing air bubble in the CPD.
The accumulation and coalescence stages repeat, until the CPD reaches a critical weight, then the CPD
finally breaks up to produce a compound drop. For the air/SDS-solution system, the bubbles in the CPDs
do not coalesce, and the contact line of the CPDs initially climbs along the capillary and then moves
downwards with the growth of the CPDs. The upstream velocity fluctuates during the periodical formation
and breakup of the CPD due to Laplace pressure variation at the tip of the glass capillary. By adding
surfactant into water, the fluctuation of the upstream velocity decreases. The size distribution of the compound
drops produced by the breakup of CPDs is quantified, and the results show that the current system
is able to produce monodisperse compound drops.
Subject
DRNTU::Engineering::Mechanical engineering
Type
Journal Article
Series/Journal Title
International journal of heat and mass transfer
Rights
© 2011 Elsevier. This is the author created version of a work that has been peer reviewed and accepted for publication by International journal of heat and mass transfer, Elsevier. It incorporates referee’s comments but changes resulting from the publishing process, such as copyediting, structural formatting, may not be reflected in this document. The published version is available at: http://dx.doi.org/10.1016/j.ijheatmasstransfer.2011.10.008.
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http://dx.doi.org/10.1016/j.ijheatmasstransfer.2011.10.008
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