Date of Award

10-5-2017

Degree Type

Thesis

Degree Name

M.A.Sc.

Department

Mechanical, Automotive, and Materials Engineering

First Advisor

Ting, David

Second Advisor

Carriveau, Rupp

Keywords

bubble ring, buoyant vortex ring, fluid mechanics, torus, wind tunnel

Abstract

A vortex ring is a torus-shaped vortex consisting of a region of fluid spinning around an imaginary axis line that forms a closed loop. It is an important phenomenon in animal kingdom and engineering applications. Birds and flying insects use buoyant vortex ring to glide higher altitudes; squid and jellyfish produce vortex rings during propulsion; vortex rings also participate in the blood flow through the human hearts. With the help of the vortex ring, animals can move fast and produce large thrust. In engineering, the Underwater Compressed Air Energy Storage (UWCAES) system uses surplus electricity to compress air into flexible accumulators (balloons) to store energy underwater. Balloons of stored compressed air may rupture when over-pressurized or pierced by a sharp object. This may generate a large-scale buoyant vortex ring, leading to water surface disruptions and undesirable waves. As a result, it is a necessity to study the hydrodynamics of a buoyant vortex ring. This work presents three papers to have a better understanding of the fluid dynamics of a buoyant vortex ring. The first two papers focus on the flow behavior of a buoyant vortex ring and the third paper studies the vortex rings’ influence on the ambient fluid (flow behind a buoyant vortex ring). The first paper characterized the formation conditions of a buoyant vortex ring and its transition behavior from a laminar to a turbulent vortex ring. It is followed by a paper investigating the flow characteristics of a buoyant vortex ring experimentally, including rising velocity, ring radius, relative core size, circulation and the energy development of a buoyant vortex ring. The final paper analyzed the wake of a vortex ring by simplifying that the core of a vortex ring is solid. This part of the work was conducted in a closed loop wind tunnel.

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