Graduation Year

2021

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Mechanical Engineering

Major Professor

David W. Murphy, Ph.D.

Committee Member

Rasim Guldiken, Ph.D.

Committee Member

Andres Tejada-Martinez, Ph.D.

Committee Member

Gary Mitchum, Ph.D.

Committee Member

Damian Grundle, Ph.D.

Keywords

Bubble size, Film droplets, Film retraction, Jet speed, Primary vortex

Abstract

The bursting of bubbles at an air-liquid interface is an important physical process in many environmental and industrial applications. Bubble bursting has implications for climate (e.g. marine aerosol formation; Veron 2015), human respiratory health (e.g. aerosolization of harmful substances; Prather et al 2013), food science (e.g. beer and champagne bubbles; Liger-Belair et al 2009), industry (e.g. processes such as gas fluxing and electrowinning; Zhang et al 2011), and volcanology (e.g. Strombolian eruptions; Chojnicki et al 2015). Much of the previous research into bubble bursting has focused on the fluid dynamics of the liquid component, namely the bubble cap film rupture and retraction and the generation of liquid droplets (e.g. jet drops and film drops). However, the fluid dynamics of the pressurized gas escaping from inside the bursting bubble is not well understood. Prior work and preliminary flow visualization results presented here show that this gas forms a high speed jet which rolls up into a vortex ring that may travel a long distance (Rogers 1858), but the fluid dynamics of this process as a function of bubble properties (e.g. size, liquid viscosity, surface tension) is not known.

In this study, I aim to explore the fluid dynamics of the gas escape from bursting bubbles using a stereophotogrammetric high speed camera system. This system allows to quantitatively visualize in three dimensions the bursting of smoke-filled bubbles resting atop a liquid surface and the subsequent release of smoke jets and vortex rings. Further, I intend to vary the size of these single bubbles and the surface tension and viscosity of their comprising fluid in order to perform a scaling analysis. More specifically, I present measurements of parent bubble characteristics and its emerging smoke jet in high spatial and temporal resolutions to better interpret the nondimensionally-scaled relationship. In a different vein, I show measurements of the parameters of the emitted vortex ring at early formation and its subsequent growth, entrainment, and travel distance. Finally, I investigate the interaction between the emanating smoke jet and the film retraction process to further explain the role of droplet ejection on the formation of additional vortices.

Understanding the fluid dynamics of gas jets and vortex rings released from bursting bubbles could lead to novel applications in industry or food science. For example, bubble properties could be tuned to enhance transport of pleasurable odors released from bursting champagne bubbles or decrease mixing of harmful gases released from bubbles while gas fluxing molten aluminum. Further, the gas jets and vortex rings created from bursting bubbles could carry newly or previously formed aerosol particles far from their generation site. These flows are thus likely important in the lofting of marine aerosol particles from near the ocean surface into the atmosphere, but the interaction between these air flows and fine droplets is not well understood. This study will thus establish a new understanding of a fundamental flow important in myriad applications.

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