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简介：Theunsteadyhydrodynamicsofabiomimeticfinattachedtoacylindricalbodyhasbeenstudiednumericallyusingacomputationalfluiddynamic(CFD)simulatorbasedonanin-housesolveroftheNavier-Stokesequations,combinedwitharecentlydevelopedmulti-block,oversetgridmethod.Thefin-bodyCFDmodelisbasedonamechanicalpectoralfindevice,whichconsistsofacylindricalbodyandanasymmetricfinandcanmimicflapping,rowingandfeatheringmotionsofthepectoralfinsinfishes.Firstthemulti-block,oversetgridmethodincorporatedintotheNSsolverwasverifiedthroughanextensivestudyofunsteadyflowspastasinglefinundergoingrowingandfeatheringmotion.Thenunsteadyflowspastthebiomimeticfin-bodymodelundergoingthesamemotionswerecomputedandcomparedwiththemeasurementsofforcesofthemechanicalpectoralfin,whichshowsgoodagreementinbothtime-varyingandtime-averagedhydrodynamicforces.Therelationshipbetweenforcegenerationandvortexdynamicspointstotheimportanceofthematchinfinkinematicsbetweenpowerandrecoverystrokesandimpliesthatanoptimalselectionofparametersofphaselagsbetweenandamplitudesofrowingandfeatheringmotionscanimprovetheperformanceoflabriformpropulsionintermsofeithermaximumforcegenerationorminimummechanicalpower.

简介：Fishesarefamousfortheirabilitytopositionthemselvesaccuratelyeveninturbulentflows.Thisabilityistheresultofthecoordinatedmovementoffinswhichextendfromthebody.Wehaveembarkedonaresearchprogramdesignedtodevelopanagileandhighefficientbiologicallyinspiredroboticfishbasedontheperformanceofhybridmechanicalfins.Toaccomplishthisgoal,amechanicalray-likefinactuatedbyShapeMemoryAlloy(SMA)isdeveloped,whichcanrealizebothoscillatorylocomotionandundulatorylocomotion.Wefirstgiveabriefintroductiononthemechanicalstructureofourfinandthencarryouttheoreticanalysisonforcegeneration.DetailedinformationofthesetheoreticalresultsislaterrevealedbyComputationalFluidDynamic(CFD),andisfinalvalidatedbyexperiments.Thisroboticfinhaspotentialapplicationasapropulsorforfutureunderwatervehiclesinadditiontobeingavaluablescientificinstrument.

简介：ThispaperdealswithanexperimentalinvestigationofpinfinboilingofsaturatedandsubcooledHFE-7100underatmosphericpressure.Finbasetemperatureandheatfluxdataaremeasuredalongwiththefintiptemperature.ThebasicfeaturesofboilingstabilityofHFE-7100boilingonpinfinhadbeenreportedforthefirsttime.Foragivenliquid/heatingsurfacecombinationthereexistuppersteady-state(USS)branchandlowersteady-state(LSS)branch,andalarge,unstableregimelocatedinbetween.Zoneswithdifferentstabilitycharacteristicsaremappedaccordingtoboilingonfinswithdifferentaspectratios.Liquidsubcoolingcanlargelyenhanceheattransferperformance.Alongerfincanprovideasaferoperation.

简介：Wecomputethewakeofatwo-dimensionalandthree-dimensionalflexiblefininanunsteadyflowfieldwithheavingandpitchingmotionsusingFLUENT.Deflexionmodeisusedforanon-uniformcantileverbeamwithnon-uniformlydistributedload.Theeffectofchordwisedeflexionlengthonthecharacteristicsofpropulsionisdiscussedfortwo-dimensionalflexiblefin.Thethrustcoefficientdecreases,propulsiveefficiencyincreasesandtheintensityofturbulenceattenuatesgraduallyasthedeflexionlengthincreases.Forathree-dimensionalflexiblefin,theintensityofthevortexintheplaneofsymmetryishigherthanthatintheplaneat3/4spanlengthofthecaudalfin.Butthepropulsiveperformanceachievedisnotwhatweexpectedwiththegivendeflexionmode.

简介：Anexperimentalstudywascarriedouttoinvestigatetheinfluenceofdoubletwisted-tapeinserts(DTs)inmicro-fintubes(MFs)onheattransfer,frictionfactorandthermalperformancefactorcharacteristicsofthecompounddevicesinthefollowingconfigurations:(1)twistedtapesactedinthesamedirection(forco-swirl)whileMFandtwistedtapesactedinthesame(parallel)direction(MF-CoDTs:P),(2)twistedtapesactedinthesamedirection(forco-swirl)whilemicro-fintubeandtwistedtapesactedinoppositedirections(MF-CoDTs:O)and(3)twistedtapesactedinoppositedirectionsforcounterswirl(MF-CDTs).TheMFaloneandtheMFequippedwithasingletwistedtapeinparallel/oppositearrangementwerealsoconsideredforcomparison.TheexperimentswereconductedfortheflowswiththeReynoldsnumbersbetween5650and17000,underuniformheatfluxcondition.TheexperimentalresultsindicatethatMF-CDTsinducestrongerswirl/turbulenceflow,resultinginhigherheattransferrate,frictionfactorandthermalperformancefactorthanothercombineddevices.ThethermalperformancefactorsassociatedwiththeuseofMF-CDTswerefoundtobehigherthanthoseassociatedwiththeusesofMF-CoDTs:P,MF-CoDTs:OandMFaloneupto9.3%,6.5%and56.4%,respectively.TheempiricalcorrelationsdevelopedusingthepresentexperimentaldatafortheNusseltnumber,frictionfactorandthermalperformancefactorarealsoreported.

简介：Biomimeticdesignemploystheprinciplesofnaturetosolveengineeringproblems.Suchdesignswhicharehopedtobequick,efficient,robust,andversatile,havetakenadvantageofoptimizationvianaturalselection.Inthepresentresearch,anenvironment-friendlypropulsionsystemmimickingundulatingfinsofstingraywasbuilt.Anon-conventionalmethodwasconsideredtomodeltheflexibilityofthefinsofstingray.Atwo-degree-of-freedommechanismcomprisedofseverallinkageswasdesignedandconstructedtomimictheactualflexiblefin.Thedrivinglinkageswereusedtoformamechanicalfincon-sistingofseveralfinsegments,whichareabletoproduceundulations,similartothoseproducedbytheactualfins.Owingtothemodularityofthedesignofthemechanicalfin,variousundulatingpatternscanberealized.Somequalitativeobservations,obtainedbyexperiments,predictedthatthethrustsproducedbythemechanicalfinaredifferentamongvariousundulatingpatterns.Tofullyunderstandthisexperimentalphenomenonisveryimportantforbetterperformanceandenergysavingforourbioroboticunderwaterpropulsionsystem.Here,fourbasicundulatingpatternsofthemechanicalfinwereperformedusingtwo-dimensionalunsteadycomputationalfluiddynamics(CFD)method.Anunstructured,grid-based,unsteadyNavier-Stokessolverwithautomaticadaptivere-meshingwasusedtocomputetheunsteadyflowaroundthefinthroughtwentycompletecycles.Thepressuredistributiononfinsurfacewascomputedandintegratedtoprovidefinforceswhichweredecomposedintoliftandthrust.Thepressureforceandfrictionforcewerealsocomputedthroughouttheswimmingcycle.Finally,vortexcontourmapsofthesefourbasicfinundulatingpatternsweredisplayedandcompared.

简介：Amodelwasestablishedtopredictcondensationheattransfercoefficientonhorizontalrectangularfinnedtube.Drop-Offzoneatthetubebottomwasconsideredanddetermined,theknownHonda(andOwen)expressionofretentionanglewasalsomodifiedasaresultofconsideringdrop-offzone.Heatfluxonfintipsintheunfloodedregion,finflanks,finspacingsandfintipsinthefloodedregionwereanalyzedrespectively.COndensationonfintipsinemphasizedbyconsideringthevariationoffilmthicknessalongcircumferenceaswellashorizontally.FInefficiencywasconsideredincalculation.Thepredictionresultswerecomparedwithseveralresearchers'experimentaldataforthreekindsofworkingfluidsonsevendifferenttubegeometriesandforvarioustemperaturedifferences,Thesedataunderabout60testconditionswerepredictedwithdiscrepancyof±10%.PredictionbythepresentmodelforsteamandR-113condensationwerecomparedwithpreviousmodels.

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简介：Generallytheunderwaterbio-robotstakethetailfinaspropulsor,andcombinedwithpectoralfintheycanmanoeuvreagilelyandcontroltheirpositionandmovementatwill.Innature,alotoffishesrealizetosuspenditselfinwatertogoforwardandtomovebackupbythepectoralfinmovingcomplexly.Sothatitissignificanttheoreticallyandvaluableforpracticalapplicationtoinvestigatethepropulsiveprincipleandhydrodynamicperformanceofpectoralfin,andfindthemethodutilizingthepectoralfintomanoeuvretheunderwaterbio-robotagilely.Inthispaper,atwodegreeoffreedom(DoF)motionmodelisestablishedforarigidpectoralfin,andthehydrodynamicperformancesofthepectoralfinarestudiedbyuseofthepectoralfinpropulsiveexperimentalplatformdevelopedbyHarbinEngineeringUniversity,simultaneouslythehydrodynamicperformanceofthepectoralfinisanalyzedwhensomeparameterschange.Then,throughthesecondarydevelopmentofFLUENT(CFDcode)software,thehydrodynamicperformancesofrigidpectoralfininviscousflowsarecalculatedandtheresultsarecomparedwiththelatestexperimentalresults.Theresearchinthispaperwillprovidethetheoreticalreferenceforthedesignofthemanoeuvringsystemimitatingpectoralfin,atthesametimewillbecomethefoundationforthedevelopmentofthesmallunderwaterbio-robot.

简介：Theuseofoscillatingflexiblefinsinpropulsionhasbeenthesubjectofseveralstudiesinrecentyears,butattentionisrarelypaidtothespecificroleofstiffnessprofileinthrustproduction.Stiffnessprofileisdefinedasthevariationinlocalchordwisebendingstiffness(EI)ofafin,fromleadingtotrailingedge.Inthisstudy,flexiblefinswithastandardNACA0012shapeweretestedalongsidefinswithastiffnessprofilemimickingthatofaPumpkinseedSunfish(Lepomisgibbosus).Thefinswereoscillatedwithapitchingsinusoidalmotionoverarangeoffrequenciesandamplitudes,whiletorque,lateralforceandstaticthrustweremeasured.Overtherangeofoscillationparameterstested,itwasshownthatthefinwithabiomimeticstiffnessprofileofferedasignificantimprovementinstaticthrust,comparedtoafinofsimilardimensionswithastandardNACA0012aerofoilprofile.Thebiomimeticfinalsoproducedthrustmoreconsistentlyovereachoscillationcycle.Acomparisonoffinmaterialsofdifferentstiffnessshowedthattheimprovementwasduetothestiffnessprofileitself,andwasnotsimplyaneffectofalteringtheoverallstiffnessofthefin.Finsofthesamestiffnessprofilewereobservedtofollowthesamethrust-powercurve,independentofthestiffnessofthemouldingmaterial.Biomimeticfinswereshowntoproduceupto26%greaterthrustperwattofinputpower,withintheexperimentalrange.

简介：Finstabilizerswithfin-liftfeedbackcontrolcanshieldthemappingerrorofcalculationbetweenthefinangleandfinliftforce,whichisinthefinstabilizerwithfin-anglefeedbackcontrol.Inpractice,therearesometechnicaldifficultiesinliftfinstabilizers,suchasliftforcedetectionandliftforcesensorinstallation,soitcannotachievethegoodantirollingperformance.Therefore,afinstabilizersystemwithfin-lift/fin-angleintegratedcontrolisbroughtforward.Datafusionbasedonwaveletdenoisingtechnologyisemployedinthesystem,whichcombinesliftwithfinanglelocalinformationfromtwosensorswithdifferentfrequencyrangesinordertoeliminateredundantandcontradictoryinformation,andusingcomplementaryinformationtoobtaintherelativeintegrityoftheliftforcesignal.Thesystemmodelisestablishedinthispaper,andthefusionsignalandtheantirollingperformanceofthismodelaresimulatedrespectively.Theresultshowsthatthecontrolsystemcanmeettheantirollingneedindifferentseasituations.

简介：Numericalinvestigationwasconductedonanairshipofhull-finconfigurationforaerodynamicandaeroelasticcharacteristicsinthree-dimensionalviscousflows.Themathematicalmodelwasbuiltandthecorrespondingnumericalcodewasdevelopedforthefluid-structureinteractionproblem.ThegoverningequationsoftheviscousflowwithLL-LowReynoldsmodifiedmodelweresolvedbythestandardSIMPLEalgorithmbasedonthefinitevolumemethod.Afluid-structurecoupledmethodwasemployedtosolvethenonlinearaeroelasticityproblemfortheairship.Thecomputationalresultsoftheviscousflowareingoodagreementwiththeexperimentalmeasurements.Thesimulationontheaeroelasticbehavioroftheairshipinatrimmedflightrevealstheeffectofstructureflexibilityontheaerodynamicperformance.

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简介：试验性的调查被执行在与不同模式的短矩形的板鳍的数组(7脳7)适合的endwall上学习液体流动和热转移特征(co尖并且之字形)为不同沥青比率。实验在50公里高度的矩形的管被进行因为雷纳兹数字的空气流动基于相等的直径和管的空气速度从18750～62500。红外线的图象分析技术被采用在鳍底，endwall和全面表面上弄明白本地热转移系数的特征。在短矩形的盘子附近的流动模式被导致设想荧光灯在一条水隧道和纵的旋涡的染料被观察。为co尖的模式在流动方向原因热转移改进增加在盘子之间的距离，当减少时为之字形模式的距离原因热转移改进。有沥青比率2的之字形模式被发现比调查的任何另外的案例在发情转移改进更有效。关键词红外线的图象-矩形的板-传送对流热转移-流动可视化CLC数字TK124

简介：Oneofmanyinterestingresearchactivitiesinbiofluidmechanicsisdedicatedtoinvestigationsoflocomotioninwater.Someofpropulsionmechanismsobservedintheunderwaterworldareusedinthedevelopmentprocessofunderwaterauto-nomicvehicles(AUV).Inordertocharacteriseseveralsolutionsaccordingtotheirmanoeuvrability,influenceonthesur-roundingfluidandenergeticefficiency,adetailedanalysisoffin-likemovementisindispensable.Inthecurrentpaperananalysisofundulatory,oscillatoryandcombinedfin-likemovementsbymeansofnumericalsimulationiscarriedout.TheconservationequationofmassandtheconservationequationofmomentumaresolvedwiththeFiniteVolumeMethod(FVM)byuseofthesoftwareCFX-10.0.Theundulatoryandoscillatoryfinmovementsaremodelledwithanequationthatisimplementedwithinanadditionalsubroutineandjoinedwiththemainsolver.Numericalsimulationsarecarriedoutinthecomputationaldomain,inwhichonefinisfixedinaflow-throughwaterduct.SimulationsarecarriedoutintherangeoftheRenumberupto105.Theresultsshowsignificantinfluenceofappliedfinmotiononthevelocitydistributioninthesurroundingfluid.

简介：Thispaperaddressesthedesignofabiomimeticfishrobotactuatedbypiezoceramicactuatorsandtheeffectofartificialcaudalfinsonthefishrobot'sperformance.Thelimitedbendingdisplacementproducedbyalightweightpiezocompositeactuatorwasamplifiedandtransformedintoalargetailbeatmotionbymeansofalinkagesystem.Caudalfinsthatmimictheshapeofamackerelfinwerefabricatedforthepurposeofexaminingtheeffectofcaudalfincharacteristicsonthrustpro-ductionatanoperatingfrequencyrange.Thethicknessdistributionofarealmackerel'sfinwasmeasuredandusedtodesignartificialcaudalfins.ThethrustperformanceofthebiomimeticfishrobotpropelledbyfinsofvariousthicknesseswasexaminedintermsoftheStrouhalnumber,theFroudenumber,theReynoldsnumber,andthepowerconsumption.Forthesamefinareaandaspectratio,anartificialcaudalfinwithadistributedthicknessshowsthebestforwardspeedandtheleastpowercon-sumption.

简介：Heattransferinpassagewithpin-finarraysforcoolingbladetrailingedgewasstudiednumerically.Three-dimensionalnumericalsimulationswerecarriedoutforsteadylaminarflowinpassageswithdifferentwedgeanglesbetweenpressuresurfaceandsuctionsurfaceofcoolingbladetrailingedgetostudytheeffectofdifferentwedgeangles(from0°to30°)onheattransferandpressurelosses.Researchwascarriedoutforbothin-linearrayandstaggeredarray.Fromthisinvestigation,wedgeangle10°givesthebestheattransferperformance.

简介：Presentsthefin-propellertestset-uptosolvetheproblemofrollstabilizationwithshipsinfullspeedrange,withwhich,testswereruninwaterrankforacquisitionofdata,andconcludesfromdataacquiredthatthefin-propellertestset-upproducesmoreliftthansimplefin,andprovideslateralthrustaswell,anditisthereforeaneffectiverollstabilizationdeviceforshipsinfullspeedrange.

简介：Throughanalyzingtherollmodeloftheintegratedsystemoffinandanti-rollingtank,thispaperusesbinomialequationtosimplifythemoduleandcheckhowtheapproximateparameterssimulatetheoriginalfunction.Basedonthesimplifiedmodule,theinfluenceoffinandanti-rollingtankonthecoefficientitemsoftherollmoduleisdiscussed,andtheinfluencingfactorsbetweenfinandanti-rollingtankareanalysed.Andthroughsimulation,theinfluenceofactionbetweenfinandanti-rollingtankonthestaticcharacteristics,andtheintegratedstabilizationeffect,areanalyzed.