简介:Fishareabletomakegooduseofvortices.Inacomplexflowfield,manyfishcontinuetomaintainbothefficientcruisingandmaneuverability.Traditionalman-madepropulsionsystemsperformpoorlyincomplexflowfields.Withfish-likepropulsionsystems,itisimportanttopaymoreattentiontocomplexflowfields.Inthispaper,theinfluenceofvorticesonthehydrodynamicperformanceof2-Dflapping-foilswasinvestigated.Theflapping-foilheavedandpitchedundertheinfluenceofinflowvorticesgeneratedbyanoscillatingD-sectioncylinder.Anumericalsimulationwasrunbasedthefinitevolumemethod,usingthecomputationalfluiddynamics(CFD)softwareFLUENTwithReynolds-averagedNavier-Stokes(RANS)equationsapplied.Inaddition,dynamicmeshtechnologyandpostprocessingsystemswerealsofullyused.Thecalculationsshowedfourmodesofinteraction.Thehydrodynamicperformanceofflapping-foilswasanalyzedandtheresultscomparedwithexperimentaldata.Thisvalidatedthenumericalsimulation,confirmingthatflapping-foilscanincreaseefficiencybyabsorbingenergyfrominflowvortices.
简介:Inordertostudytheeffectsofgeometricparametersoftherudderonthehydrodynamicperformanceofthepropeller-ruddersystem,thesurfacepanelmethodisusedtobuildthenumericalmodelofthesteadyinteractionbetweenthepropellerandruddertoanalyzetherelevantfactors.Theinteractionbetweenthepropellerandrudderisconsideredthroughtheinducedvelocities,whicharecircumferentiallyaveraged,sotheunsteadyproblemistranslatedtosteadystate.Aniterativecalculationmethodisuseduntilthehydrodynamicperformanceconverges.Firstly,thehydrodynamicperformanceofthechosenpropeller-ruddersystemiscalculated,andthecomparisonbetweenthecalculatedresultsandtheexperimentaldataindicatesthatthecalculationprogramisreliable.Then,thevariableparametersofrudderareinvestigated,andthecalculationresultsshowthatthepropeller-rudderspacinghasanegativerelationshipwiththeefficiencyofthepropeller-ruddersystem,andtherudderspanhasanoptimalmatchrangewiththepropellerdiameter.Futhermore,therudderchordandthicknessbothhaveapositivecorrelationwiththehydrodynamicperformanceofthepropeller-ruddersystem.
简介:GiventherecentsuccessinthedevelopmentofseveralsubmersiblesinChina,people’sinterestinthehistoryofsubmersibledevelopmentisincreasing.ThispaperpresentsthehistoryofsubmersibledevelopmentinChina,whichcanbebrieflydividedintothreeperiods.Thefirstoneistheearlyperiodofhardship(1971–2000).ManyprototypesubmersiblesofHOVs,ROVs,andAUVsweredevelopedatthistime,butthemainachievementwastheestablishmentofspecialresearchorganizationsandthetrainingofresearchanddevelopmentpersonnel.Thesecondperiodcanberegardedasthequickdevelopmentperiod(2001–2015).Allcurrentlyusedsubmersiblesweredevelopedduringthisperiod.Themostremarkableachievementwasthesuccessfuldevelopmentof7000m-deepmannedsubmersibleBJiaolong.^Thethirdperiodaimstodevelop11000msubmersiblesforchallengingthefulloceandepth(2016–2020).Inthisperiod,twounmannedsubmersiblesandtwomannedsubmersibleswillbethesignificantindicatorsofachievement.Ifthis5-yearplancanbesuccessfullycompleted,Chinacanplayasignificantroleintheinvestigationofthedeepestpartoftheoceans,namely,thehadaltrenches(6500–11000m).
简介:Applicationsofcomputationalfluiddynamic(CFD)tothemaritimeindustrycontinuetogrowwiththeincreasingdevelopmentofcomputers.Numericalapproacheshaveevolvedtoalevelofaccuracywhichallowsthemtobeappliedforhydrodynamiccomputationsinindustryareas.Hydrodynamictests,especiallyplanar-motion-mechanism(PMM)testsaresimulatedbyCFDsoftware-FLUENT,andallofthecorrespondinghydrodynamiccoefficientsareobtained,whichsatisfytheneedofestablishingthesimulationsystemtoevaluatemaneuverabilityofvehiclesduringtheautonomousunderwatervehicleschemedesignstage.Theestablishedsimulationsystemperformedwellintests.
简介:Inordertostudycavitationcharacteristicsofa2-Dhydrofoil,themethodthatcombinesnonlinearcavitationmodelandmixed-iterationisusedtopredictandanalyzethecavitationperformanceofhydrofoils.ThecavitationelementsarenonlinearlydisposedbasedontheGreenformulaandperturbationpotentialpanelmethod.Atthesametime,themethodthatcombinescavityshapeforfixedcavitylength(CSCL)iterationandcavityshapeforfixedcavitationnumber(CSCN)iterationisusedtoworkoutthethicknessandlengthofhydrofoilcavitations.Throughanalysisofcalculationresults,itcanbeconcludedthatthejumpofpressureandvelocitypotentiallyexistbetweencavitationendareaandnon-cavitationsareaonsuctionsurfacewhencavitationoccursonhydrofoil.Incertainanglesofattack,thecavitationnumberhasanegativeimpactonthelengthofcavitations.Andunderthesameangleofattackandcavitationnumber,thebiggerthethicknessofthehydrofoil,theshorterthecavitationslength.