Coastal Bottom Boundary Layers and Sediment Transport

The following sections are included:

• PREFACE

• CONTENTS

• NOTATION

The following sections are included:

• THE BOUNDARY LAYER AND THE FLOW ABOVE IT
  • Introduction
  • Natural flows
  • Flow in laboratory models
  • Equations of motion
  • Reynolds equations for combined wave-current flows

• THE NATURE OF OSCILLATORY BOUNDARY LAYERS
  • Introduction
  • The shear stress distribution
  • Turbulence structure in oscillatory flow
  • Laminar oscillatory flow over a smooth bed
  • The wave friction factor
  • Energy dissipation due to bed friction
  • Boundary layer thickness for oscillatory flow
  • Eddy viscosity in oscillatory flow
  • Eddy viscosity for sinusoidal flow

• OSCILLATORY BOUNDARY LAYER MODELS
  • Introduction
  • Quasi-steady models of oscillatory boundary layers
  • Velocity distribution models for oscillatory boundary layers
  • Eddy viscosity based models of oscillatory boundary layers
  • Higher order turbulence models for oscillatory boundary layers

• WAVE-GENERATED CURRENTS
  • Introduction
  • Eulerian drift in Stokes waves
  • Lagrangian drift in Stokes waves
  • Boundary layer drift
  • Undertow

• WAVE - CURRENT BOUNDARY LAYER INTERACTION
  • Introduction
  • Resume of steady boundary layer concepts
  • The eddy viscosity concept for combined flows
  • Turbulence intensity in combined flows
  • The influence of currents on the wave boundary layer
  • Energy dissipation by waves on a current
  • The influence of waves on current profiles
  • An empirical model for current profiles in the presence of waves
  • Wave-current interaction models with explicit consideration of

The following sections are included:

• FORCES ON SEDIMENT PARTICLES
  • Introduction
  • Intergranular forces
  • Fluid forces

• INCIPIENT SEDIMENT MOTION
  • Introduction
  • The mobility number
  • The Shields parameter
  • Skin friction and effective bed shear stress
  • The grain roughness Shields parameter
  • Critical Shields parameter and the Shields diagram
  • Initiation of motion in combined flows
  • The depth of closure

• BED-LOAD TRANSPORT IN STEADY FLOW
  • Introduction
  • What is bed-load?
  • The amount of bed-load
  • Steady bed-load and sheet-flow transport
  • Sediment speed in steady bed-load and sheet-flow

• BED-LOAD AND SHEET-FLOW UNDER WAVES
  • Introduction
  • The amount of bed-load under waves
  • Bed-load and sheet-flow under sine waves
  • Bed-load and sheet-flow under skew waves

The following sections are included:

• INTRODUCTION

• COASTAL BEDFORM REGIMES

• BEDFORM DYNAMICS
  • The continuity principle
  • Bedforms migrating with constant shape
  • Migration and growth of sinusoidal bedforms

• VORTEX RIPPLES
  • Introduction
  • Ripple length
  • Ripple steepness
  • Ripple height

• BEDFORMS IN COMBINED WAVE-CURRENT FLOWS

• HYDRAULIC ROUGHNESS OF NATURAL SAND BEDS
  • Introduction
  • Sand bed friction factors
  • Sand bed roughness in steady flows
  • Hydraulic roughness from oscillatory flow data
  • The roughness of flat sand beds under waves
  • The roughness of rippled beds under waves

The following sections are included:

• INTRODUCTION

• SETTLING VELOCITY

• EQUATION OF MOTION FOR SUSPENDED PARTICLES

• ACCELERATING SEDIMENT IN A RESTING FLUID

• SEDIMENT PARTICLES IN ACCELERATED FLOW
  • Introduction
  • Small particles in accelerated flow
  • Larger particles in homogeneous accelerated flow
  • Settling through a homogeneous, oscillatory flow
  • Sand particles in wave motions

• SEDIMENT TRAPPING BY VORTICES
  • Introduction
  • The kinematic trapping effect
  • Secondary dynamic effects

• PARTICLES SETTLING THROUGH TURBULENCE
  • Introduction
  • The loitering effect
  • Taylor's dispersion model
  • Dispersion with loitering effect

The following sections are included:

• INTRODUCTION
  • Sediment concentrations and the transport rate
  • Mixing length and sediment diffusivity
  • The bottom boundary condition

• THE NATURE OF SEDIMENT SUSPENSIONS
  • What is suspended sediment
  • Concentration measurements
  • Concentration time series
  • Time-averaged sediment concentrations
  • Time-averaged concentrations under irregular waves
  • Time-averaged concentration profiles under breaking waves
  • Different sand sizes suspended in the same flow

• PICKUP FUNCTIONS
  • Introduction
  • Pickup functions in steady flows
  • Pickup functions in unsteady flows
  • Pickup functions for sine waves over flat beds
  • Pickup functions for irregular waves over flat beds
  • Pickup functions for waves over vortex ripples
  • Selective pickup from graded sand beds

• SUSPENDED SEDIMENT DISTRIBUTION MODELS
  • Introduction
  • Convection or diffusion
  • Suspended sediment distributions due to pure convection
  • Sediment concentrations due to pure gradient diffusion
  • Sediment concentrations due to combined convection-diffusion
  • Time-averaged concentrations in combined convection-diffusion
  • Time-dependent concentrations in combined convection-diffusion
  • ɛ_s, w_c and F(z) for combined convection-diffusion
  • in combined convection-diffusion under non-breaking waves

The following sections are included:

• INTRODUCTION

• TRANSPORT MODELS : IN ESSENCE TWO VARIETIES

• SHORE NORMAL TRANSPORT OVER VORTEX RIPPLES
  • What the experimental data show
  • The gradient diffusion transport model
  • A particle trajectory model for shore normal transport over ripples
  • The grab and dump model for shore normal transport over ripples
  • Comparison of the three models

• SHORE NORMAL SEDIMENT TRANSPORT OVER FLAT BEDS
  • Introduction
  • Shore normal sediment transport in the swash zone
  • Shore normal sediment transport in the surf zone
  • Shore normal sediment transport outside the surf zone

• SHORE PARALLEL SEDIMENT TRANSPORT
  • Introduction
  • Shore parallel sediment transport outside the surf zone
  • Longshore sediment transport in the surf zone

The following sections are included:

• Introduction

• New models of wave-current boundary layer interaction

• Hydraulic roughness of flat sand beds under waves

• Instantaneous, effective shear stresses on sand beds under waves

• Bottom boundary condition for suspended sediment distributions

• Distribution models for suspended sediment

The following sections are included:

• REFERENCES

• AUTHOR INDEX

• SUBJECT INDEX