WIND GENERATED OCEAN WAVES IAN R. YOUNG

Transcription

1 ELSEVIER OCEAN ENGINEERING BOOR SERIES VOLUME 2 WIND GENERATED OCEAN WAVES IAN R. YOUNG University of Adelaide, Australia OCEAN ENGINEERING SERIES EDITORS R. Bhattacharyya & M.E. McCormick 1999 ELSEVIER Amsterdam - Lausanne - New York - Oxford - Shannon - Singapore - Tokyo

2 Contents List of Major Symbols xiii 1 Introduction 1 2 Wave Theory Introduction Small Amplitude or Linear Theory Governing Equations The Wave Profile Dispersion Relationship Wave Phase Speed Wave Length Water Particle Motion Pressure Classification with respect to Depth Wave Trains and Group Velocity Wave Transformation Basic Assumptions Wave Shoaling Wave Refraction Limitations of Linear Wave Theory Spectral Representation of Waves Frequency or Omni-directional Spectrum Directional Spectrum 23 vii

3 viii CONTENTS 3 Stochastic Properties of Ocean Waves Introduction Probability Distribution of Wave Heights The Rayleigh-Distribution Representative Measures of Wave Height Global Distribution of Wave Properties Limitations of Global Statistics 39 4 Physical Mechanisms of Wave Evolution Introduction Radiative Transfer Equation Kinematics Wave Energy Wave Spectra Source Terms Atmospheric Input, Si n Wave Induced Pressure Variations Potential Flow Jeffreys' Sheltering Theory Miles' Theory Surface Pressure Measurements Generation by Turbulent Pressure Fluctuations Nonlinear Quadruplet Interactions, S n ] Solution Techniques for S n i Properties of Quadruplet Interactions Spectral Evolution Shape Stabilization Directional Spreading White-Cap Dissipation, Sd s The Spectral Balance 80 5 Fetch and Duration Limited Growth Introduction 83

4 CONTENTS ix 5.2 Similarity Theory and Dimensionless Scaling Integral Parameters, e and v Wave Spectrum, F(f) Growth Curves for Energy and Peak Frequency The Scaling Wind Speed Fetch Limited Observations The SMB Curves The Pierson-Moskowitz Limit JONSWAP Bothnian Sea Lake Ontario North Atlantic Open Ocean Lake St. Clair Growth Rate Measurements Comparison of Fetch Limited Relationships Secondary Influences Atmospheric Stability Boundary Layer Development Gustiness of the Wind Fetch Geometry The Influence of Swell Duration Limited Observations One-Dimensional Spectrum The JONSWAP Form, oc f" The Toba Form, oc f~* The Value of the Exponent in f " n Directional Spreading Comparison of Spreading Functions Non-stationary Wind Fields Introduction The Interaction of Swell and Wind Sea Rapid Change in Wind Speed Rapid Change in Wind Direction 140

5 x CONTENTS 6.5 Hurricane Wind and Wave Fields Hurricane Wind Field Hurricane Wave Height Distribution Hurricane Wave Spectra JONSWAP Representation of Hurricane Spectra Donelan et al (1985) representation of Hurricane Spectra Finite Depth Effects Introduction Physical Processes Atmospheric Input in Finite Depth Situations, Si n Nonlinear Quadruplet Interactions in Finite Depth Situations, S n]i White-Cap Dissipation in Finite Depth Situations, Sd s Bottom Friction Dissipation, S bf Bottom Friction Coefficient, C f Typical Implementations of Bottom Friction Spectral Balance on the Finite Depth Shelf Depth Limited Breaking, S br k Limiting Total Energy Dissipation Rate Triad Nonlinear Interactions, S tri Finite Depth Growth Curves Finite Depth One-dimensional Spectra Finite Depth Directional Spreading Numerical Modelling of Waves Introduction Phase Resolving Models Boundary Integral Models Mild Slope Equation Models Boussinesq Models Phase Averaging Models 207

6 CONTENTS xi 8.4 Source Term Representation First Generation Models Second Generation Models Third Generation Models Computational Aspects Advection of Energy Computational Grids Initial and Boundary Conditions The WAM Model Prognostic Tail Discrete Interaction Approximation Evaluation of Performance Data Assimilation Ocean Wave Measurement Introduction In situ Methods Surface Following Instruments Surface Piercing Instruments Bottom Mounted Instruments Directional Instruments Surface Following Buoys Spatial Arrays Pressure-Velocity Gauges Data Analysis Spectral Analysis - F(f) Sampling Considerations Confidence Limits for Spectra Confidence Limits for Wave Height Confidence Limits for Peak Frequency Determination of Directional Spectra - F(f, 9) Fourier Expansion Method (FEM) Solution by Maximum Likelihood Method (MLM). 243

7 xii CONTENTS Other Solution Techniques A Comparison of Solution Techniques Remote Sensing Techniques Radar Altimeters Synthetic Aperture Radar (SAR) Other Radar Systems 254 Bibliography 255 Index 283