简介：Itiswellknownthatsharkskinsurfacecaneffectivelyinhabittheoccurrenceofturbulenceandreducethewallfriction,butinordertounderstandthemechanismofdragreduction,onehastosolvetheproblemoftheturbulentflowongrooved-scalesurface,andinthatrespect,thedirectnumericalsimulationisanimportanttool.Inthisarticle,basedontherealbiologicalsharkskin,themodelofrealsharkskinisbuiltthroughhigh-accuratescanninganddataprocessing.Theturbulentflowonarealsharkskiniscomprehensivelysimulated,andbasedonthesimulation,thedragreductionmechanismisdiscussed.Inaddition,inordertovalidatethedrag-reducingeffectofsharkskinsurface,actualexperimentswerecarriedoutinwatertunnel,andtheexperimentalresultsareapproximatelyconsistentwiththenumericalsimulation.

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简介：BasedonGreen’stheorem,atimedomainnumericalmodelwasconstructedtosimulatewavemakingphenomenoncausedbyamovingship.Inthisarticle,theRankinesourcesanddipoleswereplacedonboundarysurfaces(i.e.,theshipsurfaceandfreesurface),andatime-steppingschemewasemployed.Itsuniquecharacteristicisthatsteadystatecanberealizedfrominitialvaluebyemployingthetime-steppingschemeandunsteadyfreesurfaceconditions.Intimedomain,iftheresultsofunsteadyflowproblemtendtodatastabilizationaftermanytimestepsofcomputation,theycouldberegardedasthedataofsteadyones.Thismodelcouldbeemployedtosteadyorunsteadyproblems.Theoreticalreasoningandcomputationalprocessofthismethodwasdescribedindetail.Thelinearandnonlinearboundaryconditionsonbodysurfacewerestudied,andtherelativemeanstorealizetheseboundaryconditionsiniterativecomputationwerealsodiscussed.SomeproperparametersaboutthemodeloftheWigleyhullweredeterminedbymanynumericaltests,andtheirinfluencesonwavemakingresistanceandwavepatternwerediscussed.Accordingtothecomparisonbetweennumericalresultsanddataavailableinrelativereferences,themethodusedinthisworkisproventobeareliablemethodintimedomain.Andthelatticereorganizationineverytimestepcomputationisafeasiblenumericalapproach.

简介：Time-domainanalysisisusedtopredictwaveloadingandmotionresponsesforashiptravellingataconstantspeedinregularobliquewaves.Thecombineddiffractionandradiationperturbations,causedbythesteadyforwardspeedoftheshipandhermotions,areconsideredasadistributionofnormalvelocitiesonthewettedhullsurface.Theship-hullboundaryconditionisexactlyfulfilledbyexpressingthefluidnormalvelocitiesasafiniteseriesintermsofthebodygeometryandtheincidentwavepotential.Asfarastheauthorsareaware,nosimilarworkispublishedtodate.ThenewtheoryisappliedtopredictforcesandmotionsatforwardspeedforaWigleyship-hullinheadwavesandacatamaran-ferryinobliquewaves.PredictionsarecomparedwithpublishedtheoreticalandexperimentalresultsfortheWigleyship-hull,andthecomparisonisgood.Forthecatamaran,aself-propelledmodelisbuiltandtestedinthelargetowingtankandseakeepingbasinoftheChinaShipScientificResearchCentre,Wuxi

简介：Atime-domainKelvinsourcehigh-orderpanelmethodbasedonNURBSisdevelopedandappliedtosolvetheunsteadywave-makingproblems.Numericalresultsofinstantwaveresistanceandfreesurfaceelevationarepresentedandcomparedwiththeavailabyresultsbyotherauthors,forsubmergedspheroidandspherebeneaththefreesurfaceandforsurfaceshipofWigleymodelsmovingwithunsteadyspeed.Theagreementissatisfying.

简介：A3-Dtimedomainmethodisdevelopedtoinvestigatethegapinfluenceonthewaveforcesfor3-Dmultiplefloatingstructures.Specialhydrodynamicresonanceduetosmallgapsbetweenmultiplefloatingstructuresonwaveforcesisexamined.Strongandcomplicatehydrodynamicinteractionsbetweenthefloatingbodiesareobservedandthenumericalcomputationshaveprovedtheexistenceofthesharppeakforceresponseoneachfloatingbodyatsomespecialresonantwavenumbers.Bycomparisonwiththeresultsfromthefrequencydomaintechnique,theresultsobtainedfromthetimedomainmethodrevealthesimilarresonantphenomenaandhydrodynamicinteraction.TheresonantwavenumbersarealsoprovedaroundkL=nπ(n=1,2,…,∞)withacorrespondingfrequencyshift.Thestronghydrodynamicinteractionfeatureispracticallysignificantforthedesignofmodulestructuresandthelinks(connection)inwholethefloatingbodysystem.

简介：ThisworkprovidesacomprehensivetheoreticalanalysisofMHDunsteadyfreeconvectionviscoelasticfluidflowthroughaporousmedium.Themediumistreatedasincompressibleandopticallytransparent.Theflowofthefluidisinitiatedbyshearingactionofthemovingwallwithtimedependentsuction.Radiativeheatflowisconsideredintemperatureequation.Thecouplednonlinearproblemhasbeensolvedasymptotically.Approximatesolutionshavebeenobtainedforthemeanvelocity,meantemperatureusingmultiparameterperturbationtechnique.Theoriginalityofthepresentstudyistoinvestigatetheeffectofviscoelasticpropertyofthefluid(WaltersB?model)ontheflowandheattransferphenomenawhentheflowispermeatedthroughaporousmediumwithuniformporousmatrixsubjecttotransversemagneticfieldandtimedependentfluctuativesuctionattheboundarysurface.Thecaseofviscousflowhasbeendiscussedasaparticularcaseoncomparisonwiththeresultreportedearlieranditisingoodagreement.Flowreversalisindicatedincaseofviscoelasticfluidwithhighheatcapacityinthepresenceofmagneticfield.Thehighercoolingoftheplateincaseofviscoelasticflowalsocausesaflowreversal.