Bridging the Gap: New Physics in Confined Droplet Coalescence Open Access

Abstract

Coalescence is the process via which two droplets merge and become one through the formation of a "bridge" or "neck" between them which is driven by Laplace pressure. Coalescence of simple fluids in various different experimental situations has been a long studied problem with various applications in very pertinent fields. However, recently there has been a push for furthering our understanding coalescence of more than just fluids. Particular of interest is biological aggregates and colloidal systems where dissipation plays a large role. It is understood that a governing law that can describe such systems is given by Darcy's Law, a mathematical model describing fluid flow through porous materials. In this experiment we use confined droplet coalescence to understand how these systems work and what the characteristics of coalescence are. We show what the necessary conditions are to test Darcy coalescence and what an experiment might look like. Our experiments have shown that the neck width grows as a power law in time with a power of $\sim 0.4$ during coalescence. Furthermore, our work emphasizes the challenges involved in building an experimental set up that truly imitates the aggregate systems we are trying to understand. 

   

Table of Contents

Contents

1 Introduction

1.1 What is coalescence? . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.2 Applications of coalescence . . . . . . . . . . . . . . . . . . . . . . . . 2

1.3 New age of coalescence problems . . . . . . . . . . . . . . . . . . . . 2

1.4 Studying Darcy’s Law using a Hele-Shaw cell . . . . . . . . . . . . . . 6

1.5 Coalescence in a Hele-Shaw Cell . . . . . . . . . . . . . . . . . . . . . 7

2 Methods

2.1 Experimental Set Up . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2.2 Preparation and Execution . . . . . . . . . . . . . . . . . . . . . . . . 11

2.3 Growing a drop with a constant volume injection . . . . . . . . . . . 13

3 Results and Discussion

3.1 What we see . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

3.2 Time dependence of bridge growth . . . . . . . . . . . . . . . . . . . 18

3.3 Measuring curvatures . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

3.4 Variables Comparison . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.5 Comparing results to theory . . . . . . . . . . . . . . . . . . . . . . . 24

3.6 Future line of work . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

Conclusion ..........................................................27

Bibliography 29

About this Honors Thesis

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School	Emory College
Department	Physics
Degree	B.S.
Submission	Honors Thesis
Language	English
Research Field	Physics, Fluid and Plasma Biophysics, Biomechanics
Keyword	Aggregates Coalescence Fluid Coalescence
Committee Chair / Thesis Advisor	Justin C. Burton, Emory University
Committee Members	Daniel Sussman, Emory University Yiran Wang, Emory University

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