Thesis (Ph. D.)--University of Wisconsin--Madison, 1973. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.

The work contained in this thesis presents four research manuscripts concerning the flow and motion of drops and bubbles in different geometries. The first project explores the geometry of a totally wetting droplet on a conical fiber. A droplet on a fiber undergoes spontaneous motion toward the base of the fiber due to capillary forces, and viscous dissipation opposes the motion. In the first paper (Chapter 3), it was found that balancing the viscous shear force with the driving capillary force describes the motion of the droplet along the fiber. However, in nature, if fibers are coated with a liquid, there is rarely one droplet present; the second paper (Chapter 4) studies a conical fiber coated with multiple droplets. A liquid film coating a fiber will break up into droplets and it is found that the spacing of droplets depends on the shape of the fiber. The merging of droplets was studied and the dynamics well matches numerical simulations. The third paper (Chapter 5) studies the fluid film that a droplet will leave behind as it moves along the fiber. Using asymptotic matching to film deposition theory, this study found that the film thickness is affected by the curvature of the droplet. These studies show that the conical geometry and droplet curvature play an important role in droplet motion and film deposition. The last project (Chapter 6) in this thesis concerns a chain of uniform sticky bubbles that rise through an aqueous bath. It is found that the chain of bubbles will buckle regularly as it moves through a liquid bath, much like a solid rope will buckle when impacting a surface. As the bubble chain rises through the bath, a compressive force develops due to an imbalance between the buoyancy of the chain and the viscous drag of the liquid surrounding it. Unlike solid ropes, there is no bending to stabilize the bubble chain and the regular buckling pattern is unex- pected. Using scaling arguments, it is found that the viscous bath both stabilizes the chain and introduces the compressive force. The geometry of the buckling can be described from a force balance between the compressive and stabilizing forces. Drops and bubbles prove to be useful experimental tools to probe driven flow in different geometries and provide valuable insight into fundamental and applied physics systems. / Thesis / Doctor of Science (PhD)

Call number: LD2668 .T4 1959 C45

The thesis numerically models and investigates the effect of a variable water table on the soil moisture content. The modelling is done using COMSOL and Richards' equation. The temporal variation plots can be used to find the capillarity of the soil and its impact on other phenomenon such as vapor intrusion and infiltration.

The ability to manipulate colloidal particles with magnetic fields has profound applications both in industry and academic research ranging from automobile shock absorbers to robotic micro-surgery. Many of these applications use field gradients to generate forces on magnetic objects. Such methods are limited by the complexity of the required fields and by the magnitude of the forces generated. Spatially uniform fields only apply torques, but no forces, on magnetic particles. However, by coupling the particles' orientation and location, even static uniform fields can drive particle motion. We demonstrate this idea using particles adsorbed at curved liquid interfaces. We first review the intersection between active colloidal particles and (passive) particles at the fluid-fluid interface (chapter 1), followed by the introduction of magnetism, magnetic manipulation, and magnetic Janus particle fabrication techniques (chapter 2). In chapter 3, we use magnetic Janus particles with amphiphilic surface chemistry adsorbed at the spherical interface of water drop in decane as a model system to study particle response to a uniform field. Owing to capillary constraints, Janus particles adsorbed at curved interfaces will move in a uniform magnetic field to align their magnetic moment parallel to the applied field. This phenomenon is labeled as the magneto-capillary effect in this thesis. As explained quantitatively by a simple model, the effective magnetic force on the particle induced by static uniform field scales linearly with the curvature of the interface. For particles adsorbed on small droplets such as those found in emulsions, these magneto-capillary forces can far exceed those due to magnetic field gradients in both magnitude and range. The time-varying fields induce more complex particle motions that persist as long as the field is applied (chapter 4). Depending on the angle and frequency of a precessing field, particles orbit the drop poles or zig-zag around the drop equator. Magneto-capillary effects are not limited to Janus particles. Similar behaviors are observed in commercially available carbonyl iron particles. Periodic particle motion at the liquid interface can drive fluid flows inside the droplets, which may be useful for enhancing mass transport in droplet micro-reactors. The magneto-capillary effect at curved liquid interfaces offers new capabilities in magnetic manipulation: even static uniform fields can propel magnetic particles and the use of time-varying fields leads to steady particle motions of increasing complexity. These experimental demonstrations and the quantitative models that accompany them should both inspire and enable continued innovations in the use of magnetic fields to drive active processes in colloid and interface science. The final chapter highlights some specific directions for future work in this area.

The design of a fabric composite heat pipe has been completed. It is composed of two end caps, between which a fluid containment liner composed of metal foil and an outer structural layer composed of a ceramic fabric is stretched. The interior of the heat pipe is layered with a ceramic fabric wick. This heat pipe is being constructed currently at Oregon State University. The heat pipe test facility has been designed and built. Final assembly of the various components is now under way. This test facility consists of a vacuum chamber with a coolant jacket on the outside. Inside this chamber a test stand is placed which is composed of radiation shields and a supporting stand for the heat pipe and the heaters. Experimental work has been performed to ensure material compatibility of the metal foils used as a fluid containment liner. Specific materials tested include copper, aluminum, titanium, FEP teflon and three ceramic fabrics. These materials have been exposed to a variety of working fluids for up to 5000 hours at various sub-boiling temperatures. The best combinations of materials include aluminum or copper and acetone, or titanium and water. The least compatible combinations included aluminum or copper and water. An experimental apparatus to measure the wettability of candidate ceramic fabric wicks was designed and built. This apparatus included a pressure chamber to allow measurements to be taken at elevated pressures and temperatures. The liquid front velocity in one meter lengths of unwetted samples of ceramic fabrics was measured. A computer was used to determine liquid front position at 30 finite points along the fabric sample. Analysis of the data allowed calculation of a constant composed of two wicking parameters to be measured. Analysis of various analytical methods for predicting these parameters was performed. / Graduation date: 1993

The capillary surface formed within a symmetric annular tube is analyzed. Assuming identical contact angles along each boundary, we consider surfaces u(x,y) that satisfy the capillary problem on an annular region. Several qualitative properties of u are determined and in particular, the behaviour of u is examined in the limiting cases of the annular domain approaching a disk as well as a thin ring. The iterative method of Siegel is also applied to the boundary value problem and convergence is demonstrated under conditions which include a contact angle of zero. Moreover, some geometries still yield interleaving iterates, allowing for upper and lower bounds to be placed on the boundary values of u. However, the interleaving properties no longer hold universally and for other geometries, another more complex behaviour is described. Finally, a numerical method is designed to approximate the iterative scheme.

The capillary surface formed within a symmetric annular tube is analyzed. Assuming identical contact angles along each boundary, we consider surfaces u(x,y) that satisfy the capillary problem on an annular region. Several qualitative properties of u are determined and in particular, the behaviour of u is examined in the limiting cases of the annular domain approaching a disk as well as a thin ring. The iterative method of Siegel is also applied to the boundary value problem and convergence is demonstrated under conditions which include a contact angle of zero. Moreover, some geometries still yield interleaving iterates, allowing for upper and lower bounds to be placed on the boundary values of u. However, the interleaving properties no longer hold universally and for other geometries, another more complex behaviour is described. Finally, a numerical method is designed to approximate the iterative scheme.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1989. / Includes bibliographical references (leaves 114-118).

Thesis (Ph. D.)--Mechanical Engineering, Georgia Institute of Technology, 2005. / J. Carson Meredith, Committee Member ; J. Carlos Santamarina, Committee Member ; G. Paul Neitzel, Committee Member ; Richard F. Salant, Committee Member ; Jeffrey L. Streator, Committee Chair. Includes bibliographical references.