Breakup of simple and compound drops and bubbles
Abstract
Micro- and nano-scale free surface flows with interface rupture, e.g. drop or bubble breakup, are not only of fundamental scientific importance but also lie at the heart of diverse engineering applications such as ink jet printing, DNA and protein micro-/nano-arraying, and fabrication of particles and capsules for controlled release of medicines. The primary goal of this thesis is to advance the understanding of the physics of formation and pinch-off of drops and bubbles. At the start, breakup of so-called simple drops and bubbles is taken up where the ambient fluid is passive. The first problem relates to the study of the local scaling dynamics of a complex or non-Newtonian fluid as it nears the pinch-off singularity, the second addresses the study of a novel way of forming microscopic drops by using heat pulses and surface tension gradients under non-isothermal conditions, and the third concerns the first-ever reliable computational analysis of the formation of multiple drops in sequence that is supported by high-speed visualization experiments. Next, the simplest but most illustrative of two-fluid flow problems with breakup, in which a hollow annular jet whose core exerts a spatially uniform but temporally varying pressure, is analyzed to shed light on the nature of a highly unusual and unexpected type of singularity. Next, allowance is made for the time scale for the dynamical response of the core fluid to be comparable to that of the shell fluid and the long-standing problem of the nonlinear dynamics and breakup of compound jets is analyzed. Once these two problems which are free of contact lines have been successfully tackled, attention is turned to situations in which the two-fluid breakup dynamics occurs when drops and/or bubbles emerge from nozzles into an ambient fluid. First, the problems of bubble formation in a co-flowing liquid and drop formation in another fluid of infinite expanse are solved. As the centerpiece of this thesis, the long-standing problem of the dynamics of growth and breakup of compound drops from a co-extrusion nozzle is analyzed.
Degree
Ph.D.
Advisors
Basaran, Purdue University.
Subject Area
Chemical engineering
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