Wave Forces on Offshore Structures

338 Pages·2010·7.213 MB·English

by  Turgut 'Sarp' Sarpkaya

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WAVEFORCESONOFFSHORESTRUCTURES
Athoroughunderstandingoftheinteractionofwavesandcurrentswith
offshore structures has now become a vital factor in the safe and eco-
nomical design of various offshore technologies. There has been a sig-
nificant increase in the research efforts to meet this need. Although
considerable progress has been made in the offshore industry and in
the understanding of the interaction of waves, currents, and wind with
oceanstructures,mostoftheavailablebooksconcentrateonlyonprac-
tical applications without a grounding in the physics. This text strives
to integrate an understanding of the physics of ocean–structure inter-
actionswithnumerousapplications.Thismorecompleteunderstanding
will allow the engineer and designer to solve problems heretofore not
encounteredandtodesignnewandinnovativestructures.Theintentof
thisbookistoservetheneedsoffuturegenerationsofengineersdesign-
ingmoresophisticatedstructuresatever-increasingdepths.
Dr.Turgut“Sarp”Sarpkayaisaninternationallyrecognizedauthorityin
fluidmechanicsresearchandwasnamedbyCambridgeUniversityasone
oftheworld’sonethousandgreatestscientists.“Sarp,”asheisknownto
friendsandcolleagues,istherecipientoftheTurningGoalsintoReality
Award by NASA, and he was selected Freeman Scholar by the Amer-
ican Society of Mechanical Engineers (ASME). Sarpkaya received his
Ph.D.fromTheUniversityofIowa,followedbypostdoctoralworkatthe
Massachusetts Institute of Technology. He was the Thomas L. Fawick
DistinguishedProfessorattheUniversityofNebraskaandtaughtatthe
University of Manchester. He was named Professor and Chairman of
Mechanical Engineering at the Naval Postgraduate School in 1967 and
DistinguishedProfessorin1975.Hisresearchoverthepast50yearshas
coveredthespectrumofhydrodynamics.Hisoscillatingflowtunneland
thevortex-breakdownapparatusaretwoamongseveraluniqueresearch
facilitieshehasdesigned.Sarpkayahaspublishedmorethan200papers
andhasexploredfortheDefenseAdvancedResearchProjectsAgency
(DARPA)numerousclassifiedprojectsdealingwiththehydrodynamics
andhydroacousticsofsubmarines.
He served as chairman of the Executive Committee of the Fluids
Engineering Division of ASME and the Heat Transfer and Fluid
MechanicsInstitute.HeisaFellowoftheRoyalSocietyofNavalArchi-
tectsandMarineEngineers,FellowoftheASME,andAssociateFellow
oftheAmericanInstituteofAeronauticsandAstronautics.

WAVE FORCES ON OFFSHORE
STRUCTURES
Turgut “Sarp” Sarpkaya
CAMBRIDGEUNIVERSITYPRESS
Cambridge, New York, Melbourne, Madrid, Cape Town, Singapore,
São Paulo, Delhi, Dubai, Tokyo
Cambridge University Press
The Edinburgh Building, Cambridge CB2 8RU, UK
Published in the United States of America by Cambridge University Press, New York
www.cambridge.org
Information on this title: www.cambridge.org/9780521896252
© Turgut Sarpkaya 2010
This publication is in copyright. Subject to statutory exception and to the
provision of relevant collective licensing agreements, no reproduction of any part
may take place without the written permission of Cambridge University Press.
First published in print format 2010
ISBN-13 978-0-511-76418-9 eBook (Adobe Reader)
ISBN-13 978-0-521-89625-2 Hardback
Cambridge University Press has no responsibility for the persistence or accuracy
of urls for external or third-party internet websites referred to in this publication,
and does not guarantee that any content on such websites is, or will remain,
accurate or appropriate.
ThebookisdedicatedtothememoryofHermanSchlichting,
whosharedwithmehistimeandinspirationforanunforgettableyearat
AVA/Go¨ttingenin1972.

Contents
Preface pagexi
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 Classesofoffshorestructures 3
2 Reviewofthefundamentalequationsandconcepts. . . . . . . . . . . . . .7
2.1 Equationsofmotion 7
2.2 Rotationalandirrotationalflows 9
2.3 Velocitypotential 11
2.4 Euler’sequationsandtheirintegration 13
2.5 Streamfunction 15
2.6 Basicinviscidflows 16
2.7 Forceonacircularcylinderinunseparatedinviscidflow 17
2.8 Slowmotionofasphericalpenduluminviscousflow 20
2.9 Addedmassoraddedinertia 22
2.10 Anexampleoftheroleoftheaddedinertia 30
2.11 Forcesonbodiesinseparatedunsteadyflow 31
2.12 Kineticenergyanditsrelationtoaddedmass 33
3 Separationandtime-dependentflows. . . . . . . . . . . . . . . . . . . . . . .39
3.1 Introductionandkeyconcepts 39
3.2 Consequencesofseparation 42
3.3 Bodyandseparation 47
3.4 Strouhalnumber 52
3.5 Nearwakeandprincipaldifficultiesofanalysis 56
3.6 Liftortransverseforce 58
3.7 Free-streamturbulenceandroughnesseffects 58
3.8 Impulsivelystartedflows 64
3.8.1 Introductorycomments 64
3.8.2 Representativeimpulsivelystartedflows 65
vii
viii Contents
3.9 Sinusoidallyoscillatingflow 69
3.9.1 Introduction 69
3.9.2 Fourier-averageddragandinertiacoefficients 75
3.9.3 ExperimentalstudiesonC andC 76
d m
3.9.4 TransverseforceandtheStrouhalnumber 85
3.9.5 RoughnesseffectsonC ,C ,C ,andSt inSOF 90
d m L
3.9.6 AcriticalassessmentoftheMorisonequation 95
3.9.7 Oscillatoryplusmeanfloworthein-lineoscillationsofa
cylinderinsteadyflow 98
3.9.8 Forcedoscillationsofacylinderinatrough 104
3.9.9 OscillatoryflowinasmallerU-shapedwatertunnel 107
4 Wavesandwave–structureinteractions. . . . . . . . . . . . . . . . . . . . .109
4.1 Surfacegravitywaves 109
4.1.1 Linearwavetheory 110
4.1.2 Higher-orderwavetheories 115
4.1.3 Characteroftheforcespredicted 117
4.1.4 Randomwaves 119
4.1.5 Representativefrequencyspectra 121
4.2 Wave–structureinteraction 122
4.2.1 Principalfactorsofanalysisanddesign 123
4.2.2 Designwaveandforcecharacterization 125
4.2.3 Force-transfercoefficients 127
4.2.4 AbriefsummaryoftheliteraturegivingexplicitC and
d
C values 135
m
4.2.5 Suggestedvaluesforforce-transfercoefficients 138
4.2.6 Effectsoforbitalmotion,coexistingcurrent,pile
orientation,interference,andwallproximity 139
4.2.7 Pipelinesandwall-proximityeffects 155
4.2.8 Waveimpactloads 166
5 Waveforcesonlargebodies. . . . . . . . . . . . . . . . . . . . . . . . . . . . .172
5.1 Introduction 172
5.2 Thecaseoflineardiffraction 175
5.3 Froude–Krylovforce 176
5.4 Thecaseofacircularcylinder 177
5.5 Higher-orderwavediffractionandtheforceactingonavertical
cylinder 181
5.6 Closingremarks 184
6 Vortex-inducedvibrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
6.1 Keyconcepts 186
6.1.1 Nomenclature 190