船舶与海洋工程毕业设计外文翻译.docx

船舶与海洋工程毕业设计外文翻译.docx

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船舶与海洋工程毕业设计外文翻译

ASimplePredictionFormulaofRollDampingofConventionalCargoShipsontheBasisoflkeda'sMethodandItsLimitation

YukiKawahara,KazuyaMaekawaandYoshihoIkeda

DepartmentofMarineSystemEngineering,OsakaPrefectureUniversity,Sakai599-8531’Japan

Sincetherolldampingofshipshassignificanteffectsofviscosity,itisdifficulttocalculateittheoretically.Therefore,experimentalresultsorsomepredictionmethodsareusedtogettherolldampingindesignstageofships.Amongsomepredictionmethods,Ikeda’soneiswidelyusedinmanyshipmotioncomputerprograms.Usingthemethod,therolldampingofvariousshiphullswithvariousbilgekeelscanbecalculatedtoinvestigateitscharacteristics.Tocalculatetheroildampingofeachship,detaileddataoftheshipareneededtoinput.Therefore,asimplerpredictionmethodisexpectedinprimarydesignstage.SuchasimplemethodmustbeusefultovalidatetheresultsobtainedbyacomputercodetopredictitonthebasisofIkeda，smethod,too.OnthebasisofthepredictedrolldampingbyIkeda’smethodforvariousships,averysimplepredictionformulaoftherolldampingofshipsisdeducedinthepresentpaper.Shiphullformsaresystematicallychangedbychanginglength,beam,draft,mid-shipsectionalcoefficientandprismaticcoefficient.Itisfound,however,thatthissimpleformulacannotbeusedforshipsthathavehighpositionofthecenterofgravity.Amodifiedmethodtoimproveaccuracyforsuchshipsisproposed.

Keywords:

Rolldamping,simplepredictionformula,wavecomponent,eddycomponent,bilgekeelcomponent.

Introduction

In1970s,stripmethodsforpredictingshipmotionsin5-degreeoffreedomsinwaveshavebeenestablished.Themethodsarebasedonpotentialflowtheories（Ursell-Tasaimethod,sourcedistributionmethodandsoon）,andcanpredictpitch,heave,swayandyawmotionsofshipsinwavesinfairlygoodaccuracy.Inrollmotion,however,thestripmethodsdonotworkwellbecauseofsignificantviscouseffectsontherolldamping.Therefore,someempiricalformulasorexperimentaldataareusedtopredicttherolldampinginthestripmethods.

Toimprovethepredictionofrollmotionsbythesestripmethods,oneoftheauthorscarriedoutaresearchprojecttodeveloparolldampingpredictionmethodwhichhasthesameconceptandthesameorderofaccuracyasthestripmethodswhicharebasedonhydrodynamicforcesactingonstrips.ThereviewofthepredictionmethodwasmadebyHimeno[5]andIkeda[6，7]withthecomputerprogram.

Thepredictionmethod,whichisnowcalledIkeda’smethod,dividestherolldampingintothefrictional（BF）,thewave（Bw），theeddy（Be）andthebilgekeel（Bbk）componentsatzeroforwardspeed,andatforwardspeed,thelift（Bi）isadded.Increasesofwaveandfrictioncomponentsduetoadvancespeedarealsocorrectedonthebasisofexperimentalresults.ThentherolldampingcoefficientB44（=rolldampingmoment（kgfm）/rollangularvelocity（rad/sec））canbeexpressedasfollows:

B44Bbk

（1）

Atzeroforwardspeed,eachcomponentexceptthefrictionandliftcomponentsarepredictedforeachcrosssectionwithunitlengthandthepredictedvaluesaresummedupalongtheshiplength.ThefrictioncomponentispredictedbyKato’sformulaforathree-dimensionalshipshape.Modificationfunctionsforpredictingtheforwardspeedeffectsontherolldampingcomponentsaredevelopedforthefriction,waveandeddycomponents.Thecomputerprogramofthemethodwaspublished,andthemethodhasbeenwidelyused.

Forthese30years,theoriginalIkeda’smethoddevelopedforconventionalcargoshipshasbeenimprovedtoapplymanykindsofships,forexamples,moreslenderandroundships,fishingboats,barges,shipswithskegsandsoon.Theoriginalmethodisalsowidelyused.However,sometimes,differentconclusionsofrollmotionswerederivedeventhoughthesameIkeda’smethodwasusedinthecalculations.Then,tochecktheaccuracyofthecomputerprogramsofthesameIkeda’smethod,amoresimplepredictionmethodwiththealmostsameaccuracyastheIkeda’soriginalonehasbeenexpectedtobedeveloped.Itissaidthatindesignstagesofships,Ikeda’smethodistoocomplicatedtouse.Tomeettheseneeds,asimplerolldampingpredictionmethodwasdeducedbyusingregressionanalysis[8].

PreviousPredictionFormula

Thesimplepredictionformulaproposedinpreviouspapercannotbeusedformodemshipsthathavehighpositionofcenterofgravityorlongnaturalrollperiodsuchaslargepassengershipswithrelativelyflathullshape.Inordertoinvestigateitslimitation,theauthorscomparedtheresultofthispredictionmethodwithoriginalIkeda’sonewhileoutofitscalculatinglimitation.Fig.1showstheresultofthecomparisonwiththeirmethodofrolldamping.Theupperoneisontheconditionthatthecenterofgravityislowandtheloweroneontheconditionthatthecenterofgravityishigh.

Fromthisfigure,therolldampingestimatedbythispredictionformulaisingoodagreementwiththerolldampingcalculatedbytheIkeda’smethodforlowpositionofcenterofgravity,buttheerrormargingrowsforthehighpositionofcenterofgravity.Theresultssuggestthatthepreviouspredictionformulaisnecessarytoberevised.

MethodicalSeriesShips

ModifiedpredictionformulawillbedevelopedonthebasisofthepredictedresultsbyIkeda’smethodusingthemethodicalseriesships.ThisseriesshipsareconstructedbasedontheTaylorStandardSeriesanditshullshapesaremethodicallychangedbychanginglength,beam,draft,midshipsectionalcoefficientandlongitudinalprismaticcoefficient.Thegeometriesoftheseriesshipsaregivenbythefollowingequations.

ProposalofNewPredictionMethodofRollDamping

Inthischapter,thecharacteristicsofeachcomponentoftherolldamping,thefrictional,thewave,theeddyandthebilgekeelcomponentsatzeroadvancedspeed,arediscussed,andasimplepredictionformulaofeachcomponentisdeveloped.Aswellknown,thewavecomponentoftherolldampingforatwo-dimensionalcrosssectioncanbecalculatedbypotentialflowtheoriesinfairlygoodaccuracy.InIkeda'smethod,thewavedampingofastripsectionisnotcalculatedandthecalculatedvaluesbyanypotentialflowtheoriesareusedasthewavedamping.reasonwhyviscouseffectsaresignificantinonlyrolldampingcanbeexplainedasfollows.Fig.4showsthewavecomponentoftherolldampingfor2-Dsectionscalculatedbyapotentialflowtheory.

Conclusions

AsimplepredictionmethodoftherolldampingofshipsisdevelopedonthebasisoftheIkeda’soriginalpredictionmethodwhichwasdevelopedinthesameconceptasastripmethodforcalculatingshipmotionsinwaves.Usingthedataofaship,B/d,Cb，Cm,OG/d,G），bBK/B,Ibk/Lpp，（pa,therolldampingofashipcanbeapproximatelypredicted.Moreover,thelimitofapplicationofIkeda’spredictionmethodtomodernshipsthathavebuttockflowsternisdemonstratedbythemodelexperiment.ThecomputerprogramofthemethodcanbedownloadedfromtheHomePageofIkeda’sLabo（Acknowledgments

ThisworkwassupportedbytheGrant-inAidforScientificResearchoftheJapanSocietyforPromotionofScience（No.18360415）.

TheauthorswishtoexpresssincereappreciationtoProf.N.UmedaofOsakaUniversityforvaluablesuggestionstothisstudy.

References

5、Y.Ikeda,Y.Himeno,N.Tanaka,OnrolldampingforceofshipEffectsoffrictionofhullandnormalforceofbilgekeels,JournaloftheKansaiSocietyofNavalArchitects161（1976）41-49.（inJapanese）

6、Y.Ikeda,K.Komatsu,Y.Himeno,N.Tanaka,Onrolldampingforceofship~Effectsofhullsurfacepressurecreatedbybilgekeels,JournaloftheKansaiSocietyofNavalArchitects165（1977）31-40.（inJapanese）

7、Y.Ikeda,Y.Himeno,N.Tanaka,Oneddymakingcomponentofrolldampingforceonnakedhull,JournaloftheSocietyofNavalArchitects142（1977）59-69.（inJapanese）

8、Y.Ikeda,Y.Himeno,N.Tanaka,Componentsofrolldampingofshipatforwardspeed,JournaloftheSocietyofNavalArchitects143（1978）121-133.（inJapanese）

9、Y.Himeno,PredictionofShipRollDamping一StateoftheArt,ReportofDepartmentofNavalArchitecture&MarineEngineering,UniversityofMichigan,No.239,1981.

10、Y.Ikeda,PredictionMethodofRollDamping,ReportofDepartmentofNavalArchitecture,UniversityofOsakaPrefecture,1982.

11、Y.Ikeda,Rolldamping,in:

Proceedingsof1st

SymposiumofMarineDynamicsResearchGroup,Japan,1984,pp.241-250.（inJapanese）

12、Y.Kawahara,CharacteristicsofrolldampingofvariousshiptypesandasimplepredictionformulaofrolldampingonthebasisofIkeda’smethod,in:

Proceedingsofthe4thAsia-PacificWorkshoponMarineHydrodymics,Taipei,China,2008，pp.79-86.

13、Y.Ikeda,T.Fujiwara,Y.Himeno,N.Tanaka,Velocityfieldaroundshiphullinrollmotion,JournaloftheKansaiSocietyofNavalArchitects171（1978）33-45.（inJapanese）

14、N.Tanaka,Y.Himeno,Y.Ikeda,K.Isomura,

Experimentalstudyonbilgekeeleffectforshallowdraft

ship,JournaloftheKansaiSocietyofNavalArchitects180（1981）69-75.（inJapanese）

常规货船的横摇阻尼在池田方法基础上的一个简单预测方法及其局限性

YukiKawahara,KazuyaMaekawaandYoshihoIkeda

海洋系统工程部，酒井599-8531日本大阪府立大学

摘要：

由于船的横摇阻尼对其粘度有显着的影响，所以很难在理论上计算。

因此，某些实验结果或某些预测方法都被用于一般的设计阶段。

在这些预测方法中，池田方法被广泛应用于许多船舶运动的计算机程序。

使用这个方法，可以对含有各种舭龙骨的船体进行计算，从而探讨其不同的特性。

为了计算每个船的横摇阻尼，详细的数据也是必须的。

因此，在设计初期就需要更为简便的预测方法。

方法虽然简单，但也得通过电脑程序的验证并证明在池田方法的基础上是有用的。

在这个基础上推导出的简便公式就是现在的这个在本文件。

船体形式的变化是通过改变船长，船宽，吃水，中横剖面系数及棱形系数来等来等到。

然而这个简化公式不能用于具有较高的重心位置的船。

所以，一些改进的方法以提高准确行就应运而生了。

关键词：

横摇阻尼，简单的预测公式，波分量，涡分量，舭龙骨组件。

介绍

在20世纪70年代以来，船舶在波浪中的运动已发展成了具有5个自由度的运动形式，新的预测方法已经建立。

该方法是基于势流理论（Ursell-Tasai方法，源分