Document Type

Thesis - Open Access

Award Date

2018

Degree Name

Master of Science (MS)

Department / School

Civil and Environmental Engineering

First Advisor

Francis Ting

Keywords

particle separation, sediment, suspension, V3V software, vortex, wave

Abstract

Breaking waves suspend and transport large amounts of sediment particles in the surf zone. Two important aspects of the problem are the mechanism of sediment suspension and the distribution of the suspended sediment. One approach to solving this problem is to measure the sediment particles’ position and movement simultaneously with the characteristics of the flow field. Previous studies have found that sediment suspension events are related to a number of flow parameters including the vertical velocity, vorticity, horizontal velocity, turbulent kinetic energy, total shear stress, and turbulent shear stress. The objective of this study was to design and conduct an experiment that would allow for the gathering of data on the flow field and individual sediment particles simultaneously so the relationship between the characteristics of the flow field and sediment suspension and transport could be understood. The experiment was performed in a laboratory flume tilted at a slope of 2.5% with a piston type wave maker. Plunging regular waves were generated with a wave height of 0.14 m and a wave period of 3.6 s. Images of the breaking-wave-induced flow field were captured using a Volumetric Three-Component Velocimetry (V3V) system manufactured by TSI Inc. Near neutrally buoyant tracer particles were introduced in the flow to follow the fluid motion with a diameter of 54 microns and specific gravity of 1.05. The sediment particles were round white glass beads with a diameter that ranged from 0.212 to 0.25 mm and a specific gravity of 2.5. The sediment particles were separated from the tracer particles using the TSI Insight V3V 4GTM program based on the radius, intensity, percent overlap, and search tolerances of the particle images. Thirty-five tests were conducted. The measured velocity fields were studied and nine representative events were selected and analyzed in detail. The nine cases involve specific breaking-wave-generated flow structures and their interactions with the sediment. The measurements show that vertical velocity, shear stress, and vorticity were all highly related to sediment suspension. The measured data are discussed with the literature on sediment suspension by breaking waves and large-scale organized flow structures generated by other flows.

Library of Congress Subject Headings

Suspended sediments.
Waves -- Analysis.
Water waves -- Analysis.
Sediment transport.
Particles.

Description

Includes bibliographical references (pages 139-144)

Format

application/pdf

Number of Pages

161

Publisher

South Dakota State University

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Rights Statement

In Copyright