Air bubbles in liquids have complex interactions with their surroundings. A rising bubble not only mixes the surrounding fluid but also collects suspended particles such as bacteria or microplastics on its interface, transporting them to the liquid surface. When a bubble bursts, it releases droplets that carry sea salt, microorganisms, and chemicals into the air, affecting both human health and the climate. Through experiments and theory, this dissertation studies the underlying mechanisms behind bubble-mediated biofouling prevention, air-sea particle transport, and sea spray formation. Our first study examines the relationship between the flow fields created by rising bubbles and biofouling prevention on a submerged surface. Bubble aeration is a method for preventing biofouling organisms, such as barnacles, from growing on a surface without using environmentally harmful chemicals. We identify the critical flow characteristics of periodically rising bubbles that correlate with the prevention of multi-species biofouling over a seven-week period, offering a potential framework for studying and comparing flow fields that successfully inhibit biofouling. Our next study investigates how small bubbles concentrate particles adhered to the bubble interface, such as plastics or microorganisms, into highly-contaminated droplets during the bursting process. We reexamine the assumption that only particles small enough to fit within a thin microlayer around the bubble can be transported into the influential top jet drop, and demonstrate that larger particles can also be transported and exhibit higher enrichment levels than predicted. We combine experiments and theory to develop an analytical model estimating the expected enrichment based on the bubble size, particle size, and particle position on the bubble. We proceed by focusing on plastic particle transfer into the atmosphere via bursting bubbles from breaking ocean waves. Existing estimates of micro- and nanoplastic transport through this pathway have large uncertainties due to limited detection techniques and studies. We develop a modeling framework that examines the size-dependent transport of hydrophilic and hydrophobic plastic particles, revealing the dominance of jet drops over film drops and the potential for nanometer-sized plastics to become highly concentrated in the smallest drops. Finally, we explore the role of salinity on the bursting bubble production of submicron drops, which are critical to cloud formation and other atmospheric processes. It is well-known that bubbles bursting in saltier water will produce more submicron drops. However, previous studies have attributed this trend to the suppression of bubble coalescence with higher salinity, leading to more numerous bubbles and consequently more drops. We demonstrate that submicron drop production increases with salinity, even when using a salt that does not affect bubble coalescence behavior. This finding implies that salinity has a systematic effect on the physics of submicron drop formation, even at the scale of a single bubble.

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Impinging gas jets have many engineering applications, including propulsion, cooling, drying, and coating control processes. In continuous hot-dip galvanizing, a molten zinc-based coating is applied to a steel substrate for corrosion protection. Planar impinging gas jets (industrially called air-knives) are employed to wipe the protective coating from the steel sheet to control the final coating weight. The maximum skin friction and pressure gradient developed by the impinging gas jet on the steel sheet heavily influences the final coating weight. In the thesis, the maximum skin friction developed on an rigid impingement plate positioned downstream of a planar impinging gas jet (scaled-up model air-knife) is measured using oil film interferometry (OFI). A maximum skin friction map based on the jet operating conditions is established, which can be used in conjunction with industrial coating weight models for film thickness prediction, and can be further employed in the assessment and verification of computational fluid dynamic (CFD) models. As impinging gas jets reach higher flow velocities, inherent instabilities in the jet can amplify due to feedback loops created between the jet exit and the impingement plate. The flow field characteristics under resonance conditions are known to exhibit large amplitude jet column oscillations, and strong coherent fluid structures propagating down the impinging shear layers. This work examined the global effect of planar impinging gas jet oscillations on the maximum mean skin friction developed in the stagnation region using external jet forcing. Reductions in maximum mean impingement plate skin friction were confirmed and found to be caused by increased levels of fluid entrainment under jet forcing conditions. The fluctuating velocity fields under external jet forcing was also examined. The velocity fluctuations due to both the coherent motion of the jet column, and the turbulence were obtained and analyzed using fluid dynamic tools such as particle image velocimetry (PIV) and proper orthogonal decomposition (POD). The fluctuating velocity of the planar impinging gas jet displayed increased levels of fluctuation intensity and unique flow field characteristics under external forcing, as well as, exhibited similar features to that of a high speed impinging planar gas jet under fluid resonance conditions. Overall, it is determined that enhanced planar impinging gas jet oscillations (or equivalent air-knife oscillations) is associated with adverse fluid effects, which degrade the wiping performance of the jet. / Thesis / Doctor of Philosophy (PhD)

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Thesis (Ph. D.)--University of Alberta, 2009. / Title from pdf file main screen (viewed on Dec. 22, 2009). "A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Applied Mathematics, Department of Mathematical and Statistical Sciences, University of Alberta." Includes bibliographical references.

Thesis (S.M.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences and the Woods Hole Oceanographic Institution), 2002. / Includes bibliographical references (p. 75-77).

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Thesis (Ph.D.)-- University of Tulsa, 1994. / Includes bibliographical references (leaves 159-163).