Date of Award

Spring 2019

Project Type

Dissertation

Program or Major

Mechanical Engineering

Degree Name

Doctor of Philosophy

First Advisor

Christopher M White

Second Advisor

Gregory P Chini

Third Advisor

Yves Dubief

Abstract

Flow-induced erosion encompasses all processes in which fluid-solid interactions result in the

removal and transport of material from the solid. The removed material may change its physical

state and/or chemical composition and may be redeposited onto the solid body or advected away

by the fluid and deposited elsewhere. Common to all flow induced erosion processes is that they

involve an eroding surface, and eroding agent, and a fluid flow which delivers the eroding agent to

the eroding surface. Consequently, the study of erosion is difficult as it requires detailed knowledge

of the material, mechanical, and/or thermophysical properties of the eroding surface; the transport

mechanisms that deliver the eroding agent to the eroding surface; and the transport mechanisms

that entrain and advect the eroded material into and within the fluid flow. This difficulty is compounded

by the fact that that there is a feedback coupling between the eroding surface and the

fluid dynamics that control the transport mechanisms important to erosion. Specifically, during

erosion, surface morphological changes to the eroding surface will alter the flow field thereby increasing

or decreasing the rate at which the eroding agent is delivered to the eroding surface. This

in turn alters the surface morphology. Thus a complex feedback cycle exists between the fluid

and surface dynamics. The study of this feedback cycle has received little attention in the fluid

mechanics community. This relative neglect is understandable due to its non-equilibrium nature,

yet surprising when one considers how much erosion by the action of a flow is an integral part

of major scientific and engineering fields, for example geophysics, environmental, manufacturing,

and aerospace.

The underlying research objective of this dissertation is to better understand the two-way coupling

between an eroding body and the surface flux of the eroding agent by evaluating the shape dynamics of eroding bluff bodies through the erosion process. The problem is challenging since,

as described above, the surface flux of the eroding agent will vary as the surface morphology of

the eroding body evolves. In order to investigate the complex interdependence between the flow

and surface morphology of an eroding body during flow-induced erosion, physical ablation and

dissolution experiments will be performed and existing numerical datasets will be analyzed to:

(i) re-evaluate existing scaling laws regarding geometric properties (cross-sectional area, wetted

perimeter, and curvature) of bluff bodies undergoing erosion in (a) uniform, unidirectional flow,

(b) in spatially and temporally varying flow, and (c) in convectively driven flow; (ii) identify a

shape parameter of the eroding surface that is well-correlated with local evolutional changes to

the eroding agent surface flux; and (iii) develop a simple feedback erosion model that bypasses

the fluid dynamics and adjusts the local eroding agent surface flux based on the evaluation of the

identified shape parameter. The focus on the erosion of bluff bodies was chosen because, in principle,

it is more amenable to the study of the erosion feedback cycle as the evolution of the shape

dynamics and morphological changes to the surface of the eroding bluff body are a direct result of

the, unknown, instantaneous magnitude of the local eroding agent surface flux. Since the evolution

of the local eroding agent surface flux is a direct consequence of the feedback from the eroding

surface on the flow dynamics, an improved understanding of the erosion feedback cycle is possible

by evaluating only the morphological changes to the surface of the eroding bluff body.

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