High-speed & Long-time Electrostatic Measurements of Fluid & Particle Interfaces Pubblico

Abstract

Studying the inter-facial dynamics of complex systems requires non-invasive measurement techniques. During my time at Emory, I used electrostatic concepts to probe two separate systems: the dynamics of Leidenfrost vapor layers near collapse and charge decay on acoustically levitated particles. A Leidenfrost vapor layer forms between a sufficiently hot solid and an evaporating fluid. The gas-fluid and gas-solid interfaces are treated as capacitors to capture micro-second dynamics. Using this technique, a minimum Leidenfrost temperature, T-≈140°C, was found and determined to be caused by hydrodynamics alone. To expand upon experimental results, COMSOL Multiphysics simulations were conducted. Simulations uncovered a lower bound for T-, which matched the experimental results. It was determined that inertia, often assumed negligible in simulations, is paramount in determining the failure of Leidenfrost vapor layers. In the second experimental system, an acoustic levitator is coupled with an inductive Faraday cup to monitor charge decay in a non-contact manner. It was found that charge remained on particles in dry environments for weeks, contradicting the current theories. Furthermore, charge decay was found to be independent of particle composition, and instead determined by environmental factors. Finally, using a 1D sedimentation model it was determined that charge must be considered when determining how far particles can travel in Earth's atmosphere.

Table of Contents

(1) Introduction (1.1) History of the Leidenfrost effect (1.2) Acoustic levitation as a tool for isolating atmospheric particles (2) Minimum Leidenfrost Temperature on Smooth Metallic Surfaces (2.1) The failure temperature of Leidenfrost drops (2.2) Inverse Leidenfrost geometry as a reproducible experimental system (2.3) Chapter conclusions (2.4) Leidenfrost thickness measurement technique (2.4.1) Sampling protocol (2.4.2) Capacitor model of the vapor layer (3) Inertial Leidenfrost Collapse (3.1) Leidenfrost simulations couple many physics concepts (3.2) COMSOL simulation details (3.3) Lubrication model details (3.4) Chapter conclusions (4) The lifetime of charged dust in the atmosphere (4.1) Non-contact charge measurement technique (4.2) Schlieren imaging (4.3) Behavior determines the discharge behavior (4.4) 1-D sedimentation model (5) Conclusions

About this Dissertation

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School	Laney Graduate School
Department	Physics
Degree	Ph.D.
Submission	Dissertation
Language	English
Research Field	Physics, Fluid and Plasma Physics, Electricity and Magnetism Physics, Acoustics
Parola chiave	Fluid dynamics Electostatic model Leidenfrost Softmatter Physics Acoustic levitation
Committee Chair / Thesis Advisor	Justin C. Burton, Emory University
Committee Members	Saad Bhamla, Georgia Tech Eric Weeks, Emory University Luiz Santos, Emory University Kurt Warncke, Emory University

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