Hydrodynamics and sediment transport in the inner surf and swash zones

2004·11.3 MB·English

by  Puleo, Jack Anthony

HYDRODYNAMICSANDSEDIMENTTRANSPORTINTHEINNERSURFAND
SWASHZONES
By
JACKANTHONYPULEO
ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL
OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT
OFTHEREQUIREMENTSFORTHEDEGREEOF
DOCTOROFPHILOSOPHY
UNIVERSITYOFFLORIDA
2004
ACKNOWLEDGMENTS
Iamindebtedtomyadvisor.Dr.DonSlinnwhosuggestedthatIworkashis
student(firstatFloridaAtlanticandthenattheUniversityofFlorida). BecauseofDon,I
wasgivenanoutstandingopportunitytostudyunderanexcellentselectionofprofessors
usingcuttingedgenumericalmodelsanddatasets. Ialsothankmycommitteemembers.
Theireffortmadethismanuscriptmorereadableandeasiertounderstand. Mycolleagues
attheNavalResearchLaboratoryprovidedasoundhomebasewherescientificthoughts
arefreelysharedandexchanged;furtheringmyknowledgeincertainareasandproviding
newavenuesofpursuitforthisdissertationandotherworkundertakenduringmytime
enrolledatUF.
Mywife,Liles;andsons,AnthonyandCarlos,happilysupportedmeduringmy
timeatUF. Theirsmilesandlovekeptmegoing. Myparentsandextendedfamily
continuedtheirsupportandencouragementthroughthisadventure,alwaysaskingwhenI
wouldfinish. Last(reallyfirst!),IthanktheLordforgivingmetheintelligenceand
desiretofurthermyeducation. WithoutHisblessing,IwouldnotbewhereIam.
ThisworkwassupportedbytheOfficeofNavalResearch(ONR)throughfunding
totheNavalResearchLaboratoryandbygrantstoDr.DonSlinn,throughONR.
Chapters1-6arepublishedorwillbesubmittedtopeer-reviewedjournals.
Chapter1servesasabackgroundfor(andthoroughreviewof)swashzonestudiesthat
havebeencompletedoverthelastfewdecades. Thesedimenttransportportionsofthis
chapteraretobeincludedinaspecialissueonswashprocessesinContinentalShelf
Research.
11
Chapter2usesfielddatacollectedfromahighenergysteepbeachtotrytobetter
understandtheprocessesdrivingsedimenttransport. Commentsonthischapterwere
providedbyDr.ToddHolland,Dr.NathanielPlant,Dr.DonaldSlinnandDr.DanHanes.
ThisworkhassincebeenpublishedintheJournalofGeophysicalResearch(vol108,
Cl1,3350,doi:10.1029/2003JC001943,2003) andisincludedherewithpermission
fromtheAmericanGeophysicalUnion.
Chapter3presentsaremotesensingtechniqueusingvideocamerastodetermine
thespatialfieldofsurfacevelocityvectors. Thewell-knownstatisticaltechnique,particle
imagevelocimetry(PIV),wasadaptedfortheswashzoneattheNavalResearch
LaboratorybyDr.ToddHollandandmyself. Thechapterhereincludes,workthatwas
notincludedintheoriginalstudy,comparingtheopticaltechniquetothatofaradar-
basedsystem. Thiswasnecessarytofurthervalidatetheopticaltechniqueusedin
chapter4toobtainvelocityfieldsastheforcingforamorphodynamicmodel.
Comparisonsweremadetoradar-baseddatacollectedbyfellowstudentGordon
FarquarhsonandhisadvisorDr.SteveFrasieroftheUniversityofMassachusetts,
Amherst. ThisworkhassincebeenpublishedintheJournalofGeophysicalResearch
(vol108,C3,3100,doi:10.1029/2002JC001483,2003),andisincludedherewith
permissionfromtheAmericanGeophysicalUnion.
AfteracceptingthePIVtechniqueasaviableoptiontoinsitusensors,PIV
estimationswereusedinconjunctionwithvarioussedimenttransportmodelstopredict
three-dimensionalforeshoreevolution. Dr.ToddHollandandDr.TonyButtprovided
commentsandsuggestionsonthischapter. Arevisedversionofthischapterwillbe
submittedtoMarineGeology.
iii
AdeparturefromsedimenttransportistakeninChapter5,wherethesmall-scale
hydrodynamicsareinvestigatedusingafullynonlinearnumericalmodelbasedonthe
Navier-Stokesequations(previouslydevelopedatLosAlamosNationalLaboratory). Dr.
DonaldSlinnoriginallymodifiedthemodelforuseintheswashzone. BretWebbmade
modificationstoaccountforfallingwaterdropletsandairbubbles. Themodelhassince
beenmodified(byme)toincludeanewforcingalgorithm,aturbulenceclosurescheme,a
velocitycorrectionalgorithm,andnumerousotherchanges.Thischapterwillbe
submittedtotheJournalofFluidMechanics.
Chapter6furtherusesthehydrodynamicmodeltoinvestigatevelocityandshear
stressvariabilityintheswashzoneundervarioushydrodynamicconditions. Dr.Don
Slinnprovidedcommentsandsuggestions. ThischapterwillbesubmittedtoCoastal
Engineering.
IV
1
TABLEOFCONTENTS
page
ACKNOWLEDGMENTS
ii
LISTOFTABLES ix
LISTOFFIGURES
ABSTRACT
xiv
CHAPTER
1 THESWASHZONE:AREVIEWOFHYDRODYNAMICS,SEDIMENT
TRANSPORTANDFORESHORECHANGEPROCESSES
1
Introduction 1
SwashZoneFluidDynamics 4
GeneralDescriptionofSwashMotions 4
ComparisonoftheSurfandSwashZones 5
Eulerianvs.LagrangianObservations 7
Infra-GravityandHighFrequencyScalesofMotion 8
LowFrequencyMotions 8
BoresandTurbulence 13
FieldandLaboratoryStudiesofCross-shoreSwashFlows 14
ShearStressesandFrictionCoefficients 21
AlongshoreSwashMotions 24
InfluenceofGroundwaterandThroughBedFlowintheSwash 25
ThroughBedFlowEffectsonSwashZoneHydrodynamics 26
ThroughBedFlowEffectsonSwashZoneSedimentTransport 28
NumericallyModelingCross-shoreSwashMotions 31
Shoreline(leadingedge)Models 31
One-DimensionalModels 36
Navier-StokesSolvers 38
SedimentMobilizationandTransportProcesses 41
Observations 41
SedimentTransportPredictions 47
EstimationfromElevationChanges 5
ForeshoreChangeMeasurementsandPredictions 51
Conceptualmodels 51
Kinematicrelationships 52
v
1
SwashFlowStatistics 53
ForeshoreChangeModeling 55
Summary 62
2 FLUIDACCELERATIONEFFECTSONSUSPENDEDSEDIMENTTRANSPORT
INTHESWASHZONE 63
Introduction 63
IdealizedSwashMotionsandSedimentTransport 66
SuspendedSedimentTransportEquationsandtheDevelopmentoftheAcceleration.71
FieldStudy 75
Results 78
SuspendedSedimentTransportCalculation 78
Ensemble-AveragedSwashEvents 78
SuspendedSedimentObservations 81
4 SuspendedSedimentTransportPredictions 83
Discussion 89
Conclusions 95
3 COMPARISONOFOPTICALANDRADARMEASUREMENTSOFINNERSURF
ANDSWASHZONEVELOCITYFIELDS 97
Introduction 97
FieldExperiment 100
SiteLayout 100
RadarandVideoImagery 102
MethodsofVelocityExtraction 108
Radar 108
ParticleImageVelocimetry 110
Results HI
Radar-PIVcomparisons 11
Validation 118
Discussion 125
Conclusions 128
SWASHZONEFLOWFIELDSANDFORESHOREMORPHODYNAMICSONA
STEEPBEACH 131
Introduction 131
SedimentTransportModelandAccelerationParameterizations 134
FieldSiteandInstallation 137
DataExtractionMethodsandAnalysis 138
VideoStereogrammetry 138
ParticleImageVelocimetry(PIV) 145
SwashFlowStatisticsinrelationtoForeshoreChange 145
MorphodynamicModel-DataComparisons 152
Discussion 157
vi
Conclusions 159
5 NUMERICALSIMULATIONOFINNERSURFANDSWASHZONE
HYDRODYNAMICSUSINGTHEVOLUMEOFFLUIDTECHNIQUE 161
Introduction 161
Ripple 165
GoverningEquations 165
TurbulenceClosure 165
NumericalProceduresandSolutionMethod 170
ModelDomain 170
Discretization 170
Two-stepprojectionmethod 171
FreeSurface 172
InternalObstacles-AnImpermeableBeach 173
WaveForcingandBoundaryConditions 173
ModelModifications 175
DataCollection 175
Results 177
SeaSurfaceElevations 181
FlowVelocity 181
VelocityProfiles 188
MeanFlow 190
FlowAcceleration 192
Pressurefields 194
ShearStress 196
DiscussionandConclusions 200
6 NUMERICALPREDICTIONOFSWASHZONEVELOCITIESANDSHEAR
STRESSESONSTEEPSLOPES 204
Introduction 204
NumericalModelandMethods 206
Navier-StokesSolver:RIPPLE 206
ModelDomainandHydrodynamicConditions 207
Results 208
FluidVelocities 213
EstimatedSwashStressFromVelocityGradients 222
EstimatedFrictionCoefficientsFromTheDragLawFormulation 231
Conclusions 235
7 SUMMARYANDFUTUREDIRECTIONS 238
GeneralConclusions 238
BigPicture:WheretogofromHere? 240
vii
APPENDIX
A ACCURACYOFTHEFORCINGMETHODANDEFFECTOFNUMERCAL
DISSIPATION 244
B UTILITYOFTHELARGEEDDYSIMULATION 249
LISTOFREFERENCES 256
BIOGRAPHICALSKETCH 280
viii
5
1- LISTOFTABLES
2-
Table page
2-
31--1.Limitationsontypicalswashzonecurrentmeters 18
2. Limitationsontypicalswashzonesedimentsensors 45
3-
4-1.Coefficientswith95%confidenceintervalsforlinearregressions 86
5-
2. Skillandpredictionerrorforlinearregressions 90
6-
1.PIV/radartimeseriescorrelation 114
3-2. PIV/radartimeseriesstatistics 11
3.Boreceleritystatisticsforradialrange-time,PIVandDopplerborecelerities 123
1. Coefficientswith95%confidenceintervalsforlinearregressions 153
1. Percenterrorsbetweenmodelandinsitumeasurementsforseasurfaceand
horizontalvelocityintheinnersurfzone 183
1. Hydrodynamicconditionsusedforthe12cases 209
6-2. Meanstressesasafunctionofnormalizedalongslopedistanceandcasenumber..230
6-3. Frictioncoefficientestimatesusingequation6-6andthefluidvelocityfrommid
waterdepthforeachcasebasedontheregionshadedinFigures6-1and6-2....234
A-l. Rootmeansquareseasurfaceelevationserrorsasafunctionofdistanceforthe
solitarywavetestforthevariousdifferencingschemes 248
B-l. Estimateoftheturbulencelengthscalesasafunctionofcross-shoredistancefor
June19,2002 251
B-2. PercenterrorforseasurfaceelevationsintheinnersurfzoneforLESandall
reducedresolutionsimulationsascomparedtothefineresolutionnon-LES
simulation 253
IX
LISTOFFIGURES
Figure page
1-1. Schematicofoffshoreandforeshoreregionsshowingshoaling,breakingandswash
zones 2
11--2. Schematicofswashcycle 6
21--3. Schematicshowingtransferofoffshoreenergyintoswashzoneoscillations(adapted
fromMase,[1995]) 12
1-4. Ballistictheoryforleadingedgeswashmotionsfortheexcursiontrajectory(A),
cross-shorevelocity(B)andcross-shoreacceleration(C) 33
1-5. Eulerianswashflowaccelerationschematic 35
6.Flowchartforvariousmethodsofmodelingforeshorebathymetricchange 56
1.Theoreticalballisticmotionforleadingedgevelocity(A)andacceleration(B)
without(solid)andwithfriction(dashed) 67
2-2.Swashschematicfromcurrentmeterdatashowingvelocity(A)andacceleration(B)
profile 70
2-3.4-minuteswashtimeseries 76
2-4. Ensembleaverageswashtime(normalized)series;A)velocity,B)accelerationC)
Horizontalpressuregradientestimate(P),andD)suspendedload 80
2-5. Interpolatedsuspendedload(kgm‘2)asafunctionofvelocityandacceleration 82
2-6.Suspendedsedimenttransportratemeasurements(circles)andpredictions[dashed
(qB);solid(qpred)] 84
2-7.Onetoonecomparisonbetweenmeasuredsuspendedsedimenttransportratesand
thosepredictedbytheBailardmodel(A)andthemodifiedBailardmodel
includingaccelerationeffects(B) 88
2-8. TurbulentboredissipationfromtheboresinthePuleoetal.[2000]studyasa
functionoffluidacceleration 92
x