Breaking and Dissipation of Ocean Surface Waves

479 Pages·2011·10.674 MB·English

by  Alexander Babanin

BREAKING AND DISSIPATION OF OCEAN
SURFACE WAVES
Overthepast15years,ourunderstandingofthebreakinganddissipationofoceanwaves
hasundergoneadramaticleapforward.Fromaphenomenonwhichwasverypoorlyunder-
stood, it has emerged as a process whose physics is clarified and quantified. This book
presentsthestateoftheartofourcurrentunderstandingofthebreakinganddissipationof
oceanwaves.
Wave breaking is an intermittent random process, very fast by comparison with other
processes in the wave system. Distribution of wave breaking on the water surface is not
continuous,butitsroleinmaintainingtheenergybalancewithinthecontinuouswind–wave
fieldiscritical.Suchbreakingrepresentsoneofthemostinterestingandchallengingprob-
lemsforfluidmechanicsandphysicaloceanography.Oceanwavebreakingalsoplaysthe
primaryroleintheair–seaexchangeofmomentum,massandheat,anditisofsignificant
importanceforoceanremotesensing,coastalandoceanengineering,navigationandother
practicalapplications.Thisbookoutlinesthestateofwave-breakingresearchandpresents
the main outstanding problems. Non-breaking dissipation and non-dissipative effects of
breaking waves, their influence on the atmospheric boundary layer and on upper-ocean
mixing,includingextremeweatherconditions,arealsodiscussed.
Breaking and Dissipation of Ocean Surface Waves is a valuable resource for anyone
interestedinthistopic:researchers,modellers,forecasters,engineersandgraduatestudents
inphysicaloceanography,meteorologyandoceanengineering.
ALEXANDER BABANIN is a Professor in the Faculty of Engineering and Industrial
Sciences at Swinburne University of Technology, Melbourne, Australia. His bachelor’s
degree inPhysicsandmaster’sdegreeinPhysical Oceanography arefromtheFacultyof
PhysicsatLomonosovMoscowStateUniversity,andhisPh.D.onSpectralCharacteristics
ofSurfaceWindWaveFieldsisfromtheMarineHydrophysicalInstituteinSevastopol.His
researchinterestsinvolvewind-generatedwaves,air–seainteractionandoceanturbulence,
includingdynamicsofsurfaceoceanwaves,wavebreakinganddissipation,air–seabound-
arylayer,extremeoceanicconditions,wavestatistics,oceanmixingandremotesensing.

BREAKING AND DISSIPATION OF OCEAN
SURFACE WAVES
ALEXANDERV.BABANIN
SwinburneUniversityofTechnology,
Melbourne,Australia
CAMBRIDGEUNIVERSITYPRESS
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Babanin,AlexanderV.,1960-
Breakinganddissipationofoceansurfacewaves/AlexanderV.Babanin.
p. cm.
ISBN978-1-107-00158-9(Hardback)
1. Oceanwaves–Measurement. 2. Oceanwaves–Simulationmethods. I. Title.
GC205.B342011
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Contents
Preface pagexi
1 Introduction 1
1.1 Wavebreaking:theprocessthatcontrolswaveenergydissipation 2
1.2 Conceptofwavebreaking 4
2 Definitionsforwavebreaking 12
2.1 Breakingonset 13
2.2 Breakinginprogress 14
2.3 Residualbreaking 18
2.4 Classificationofwave-breakingphases 19
2.5 Breakingprobability(frequencyofoccurrence) 22
2.6 Dispersionrelationship 27
2.7 Breakingseverity 28
2.8 Typesofbreakingwaves:plunging,spillingandmicro-breaking 40
2.9 Criteriaforbreakingonset 42
2.10 Radiativetransferequation 47
3 Detectionandmeasurementofwavebreaking 49
3.1 Early observations of wave breaking, and measurements
ofwhitecapcoverageofoceansurface 50
3.2 Traditionalmeans(visualobservations) 59
3.3 Contactmeasurements 63
3.4 Laboratorymeasurementsindeterministicwavefields 69
3.5 Acousticmethods 74
3.6 Remote sensing(radar,opticalandinfraredtechniques) 93
3.7 Analytical methods of detecting breaking events in surface
elevationrecords 98
3.8 Statistical methods for quantifying breaking probability and
dissipation 112
4 Fully nonlinear analytical theories for surface waves and numerical
simulationsofwavebreaking 118
4.1 Freesurfaceatthewavebreaking 120
vii
viii Contents
4.1.1 Simulatingtheevolutionofnonlinearwavestobreaking 124
4.1.2 Simulationofthebreakingonset 134
4.1.3 Influenceofwindandinitialsteepness 136
4.2 Lagrangiannonlinearmodels 139
5 Wave-breakingprobability 142
5.1 Initiallymonochromaticwaves 143
5.1.1 Evolutionofnonlinearwavestobreaking 148
5.1.2 Measurement of the breaking onset; limiting steepness
atbreaking 150
5.1.3 Laboratoryinvestigationofwindinfluence 161
5.1.4 Distancetothebreaking 165
5.2 Wave-breakingthreshold 168
5.3 Spectralwaves 175
5.3.1 Breakingprobabilityofdominantwaves 176
5.3.2 Breakingprobabilityofsmall-scalewaves 182
5.3.3 Breakingindirectionalwavefields 199
5.3.4 Wind-forcing effects, and breaking threshold in terms
ofwindspeed 207
6 Wave-breakingseverity 219
6.1 Lossofenergybyaninitiallymonochromaticsteepwave 220
6.2 Dependenceofthebreakingseverityonwavefieldspectralproperties 227
7 Energydissipationacrossthewavespectrum 232
7.1 Theoriesofbreakingdissipation 233
7.1.1 Probability,quasi-saturatedandwhitecapmodels 234
7.1.2 Kinetic–dynamicmodel 237
7.2 Simulatingthewavedissipationinphase-resolventmodels 238
7.3 Measurementsofthewavedissipationofspectralwaves 246
7.3.1 Laboratorymeasurements 247
7.3.2 Differenceinthespectraldistributionofdissipationdueto
differenttypesofbreakingmechanisms 250
7.3.3 Fieldmeasurements 252
7.3.4 Cumulativeeffect 263
7.3.5 Whitecappingdissipationatextremewindforcing 265

7.3.6 Directionaldistributionofthewhitecappingdissipation 269
7.4 Whitecappingdissipationfunctionsinspectralmodels 272
7.5 Non-breakingspectraldissipation 295
8 Non-dissipativeeffectsofbreakingonthewavefield 322
8.1 Spectralpeakdownshiftduetowavebreaking 323
8.2 Roleofwavebreakinginmaintainingthelevelofthespectrumtail 327
8.3 Wind-inputenhancementduetowavebreaking 333
Contents ix
9 Roleofwavebreakingintheair–seainteraction 350
9.1 Atmosphericboundarylayer 350
9.1.1 Sea-dragdependenceonwavebreaking 352
9.1.2 Generationofspray 360
9.1.3 Boundarylayeratextremebreaking 371
9.2 Upper-oceanmixing 375
9.2.1 Transfer ofenergy and momentum fromthewind tothe
ocean 376
9.2.2 Generationofturbulence 384
9.2.3 Injectingthebubbles;gasexchangeacrossthesurface 396
10 Conclusions.Whatelsedoweneedtoknowaboutwavebreaking? 405
References 426
Index 461