简介：Naturalandventilatedcavitationsgeneratedonasmooth-nosedaxisymmetricbodywerestudiedexperimental-ly.Thecharacteristicsofsmallscaleandlocalizedfluctuationsof'steadycavities'weremeasuredbypressuretransducers.Comparisonsbetweennaturalandventilatedcavitiesatdiffer-entmeasuredpointsforseveralcavitationnumbersweredone.Itwasobservedthatthedominantfluctuationswereconcen-tratedinthefrequencyrangeofOHz-50Hzforallthecavitati-oncases,Similarshapesandmagnitudesofthefrequencyspectraweredetectedforbothnaturalandventilatedcavities.Muchlargerspectralamplitudeinthecavityclosureregionsuggestedasfluctuationssource.Frompartialcavitatingflowtosupercavitatingflow,thedominatfrequencyandthecorre-spondingamplitudedecreasedwithdecrasingcavitationnum-ber,whichmeantthatcavitybecamemoresteadywhiledevel-oping.

简介：Ananalyticalsolutionispresentedfortheradiationandthediffractionofacylindricalbodywithamoonpoolfloatingonthesurfaceofwaterwithafinitedepth.Theexpressionsforthepotentialsareobtainedbythemethodofseparationofvariables,andtheunknowncoefficientsaredeterminedbytheboundaryconditionsandthematchingrequirementsontheinterface.Theeffectsofthemoonpoolonthehydrodynamiccharacteristicsofthebodyareinvestigated.Somepeaksareobservedonthecurvesoftheaddedmassanddampingcoefficients,correspondingtotheresonantfrequenciesofthemoonpool.Theinternalfreesurfacemoveslikeapistonatacertainlowresonantfrequency.

简介：Comparedtootherunderwatervehicles,supercavitatingvehiclescanattainahighspeedbecausetheyeliminatedragbycreatingalargecavity,thusestablishingtheso-called"supercavitatingcondition."Suchacavityisdifficulttodevelopundernormalconditions,hence,ventilationisusedtoattainthesupercavitatingconditionintheinitialphaseofflight.Inthispaper,wefocusonthehydrodynamiccharacteristicsofaventilatedsupercavitatingvehicle.First,dynamicmodelingofthesupercavitatingvehicleisperformedtocalculatethehydrodynamicforce/momentactingonthevehicleforagivensizeofcavity.Wethendefinetherelationshipbetweentheventilationrateandthecavitationnumberbasedonanairentrainmentmodeloftheventilatedcavity.Numericalsimulationswereperformedtoanalyzethephysicalfeasibilityandcharacteristicsofthemodeling.Theresultsshowthatthecavitylength/radiusincreaseswiththeventilationrate,provingthatventilationcanbeusedtoattainthesupercavitatingcondition.

简介：Inthisstudy,theeffectofthefreesurfaceonthecloudcavitatingflowaroundabluntbodyisinvestigatedbasedonthewatertankexperimentandtheCFDmethod.Numericalresultsareingoodagreementwithexperimentaldata,andthemeshindependenceofthemethodsisverified.Thecavityevolutionprocessincludesthecavitygrowth,there-entrantjet,thecavityshedding,andthecollapse,whichcanallbeobservedfromthewatertankexperiment.Theeffectsofthefreesurfaceonthecavitylength,thethickness,andthecavityevolutionperiodareanalyzedbycomparingthedifferencebetweenthecavitatingflowsontheupperandlowersidesofthebody.Thisstudyalsoexaminestheeffectofthedistancebetweenthefreesurfaceandthemodelthroughaseriesofwatertankexperimentsandnumericalsimulations.Thecavitystabilityandasymmetry,aswellasthethicknessandthevelocityofthere-entrantjetinsidethecavity,whichvarieswiththesubmergeddepth,arediscussedwithconsiderationoftheeffectofthefreesurface.Theeffectofthefreesurfaceonthecavitatingflowaroundthebluntbodyisenhancedwiththedecreaseofthesubmergeddepth.

简介：Numericalsimulationsareperformedforlaminarnaturalconvectionheattransferfromacenteredconductingbodyenclosedinasquarecavity.Ahighaccuracyunsteadynumericalmethodisused,combiningtheuniqueconditionofthepressure,theconvergentsolutionsandthestream-functionvalueoftheinsideheat-conductingbodyaregivensimultaneously.Twoexamplesaresimulatedwiththisnumericalmethodandcomparedwiththeexperimentalresults.Theresultsofthenumericalsolutionsareconsistentwiththeexperimentalresults.Itshowsthatthenumericalmethodisvalidandfeasible.

简介：Thispaperstudiesthewall-boundedflowaroundacylindricalatahighReynoldsnumbersbodyinadeterminedcomputationaldomain,withsimulationsofthe3-D,turbulentconcentricannulusflowinastraightpipe.Numericalresultsshowthatareversingzone,appearingasatonguezonewithnestedvelocitieshigherthanthesurroundingarea,existsbehindthecylindricalbody.Theannulusspaceisaregionofhighvelocityandlowpressure.Thezerovelocity,ofcombinedtheX-velocityandtheY-velocity,existsinthecrosssectionsandnovortexsheddingisformedbehindtheattachingcylinders.Amongallinvestigatedeffectingfactors,thediametersoftheattachingandthemaincylindersaffectthewakefeaturebehindthecylindricalbodywhilethemaincylinderlengthdoesnotaffectthedistributiontendencyoftheflowfield.Thediametersofthemaincylinderandthepipeaffectthepressurevaluesandthedistributiontendenciesonthemaincylindersurface.Obviously,theincreaseofthepipediameterreducesthedragcoefficientofthecylindricalbodyandtheincreaseofthediameterofthemaincylinderincreasesthedragcoefficientgreatly.Thenumericalinvestigationoftheconcentricannulusflowprovidesfoundationsforfurtherimprovementsoftheintricateflowstudies.

简介：Thispaperisconcernedwiththewavesgeneratedbya3-Dbodyadvancingbeneaththefreesurfacewithconstantspeedinatwo-layerfluidoffinitedepth.ByapplyingGreen'stheorem,alayeredintegralequationsystembasedontheRankinesourcefortheperturbedvelocitypotentialgeneratedbythemovingbodywasderivedwiththepotentialflowtheory.Afour-nodeisoparametricelementmethodwasusedtotreatwiththesolutionofthelayeredintegralequationsystem.Thesurfaceandinterfacewavesgeneratedbyamovingballwerecalculatednumerically.Theresultswerecomparedwiththeanalyticalresultsforamovingsourcewithconstantvelocity.

简介：Inthisarticle,basedonriverqualitysimulationandsystemoptimization,awaterqualitymodelwasestablishedforscenicriverafterrainfalldischargeinfloodseason,withthetargetofmakingwaterpollutantsmeetthestandardinpriorityandsavingexpenditureonpollutioncontrol.Withtheprincipleofreducingsewagefromcombinedsewagepumpingstationandheavilypollutedinitialrainwater,amathematicalmultiobjectiveplanningmodelwasconstructedforrainsewagepollutioncontrolinfloodseason,andonescenicriverinanortherncitywastakenforsimulationexample.Theresultsshowthat:theoptimizationresultmeetstherequirementsofplanning,amongwhich,sewagereductionfromthecombinedpumpingstationaccountsfor17.38%inthetotalreductionofrainsewage,andthereductionintheheavilypollutedrainwateraccountsfor77.24%inthetotalreductionofrainwaterpumpingstation.Theplanningschemecanprovidetheoreticalbasisforpollutioncontrolofscenicriverinfloodseason,andforrationalreconstructionandlayoutofoutfallsalongtwobanksoftheriver.

简介：Inthispaper,thebuoyanttrajectoriesoflaminarfarthermalwakesbehindslenderstreamlinedheatedbodiesofrevolutioninstablestratifiedfluidhavebeeninvestigatedintheoryandexperiment.Ithasbeenfoundthatthebuoyanttrajectoriesofthermalwakesinstratifiedfluidaredifferentfromthatinhomogeneousfluid.Thebuoyanttrajectoriesofthermalwakesinstratifiedfluidarewavy.Thefactorsinfluencingthebuoyanttrajectoriesofaxisymmetriclami-narthermalwakesinstratifiedfluidareRichardsonnumber,Nusseltnumberandnumber.Thevalidityoftheoreticalanalysishasbeenprovedbytheresultsofmeasurementsandvisualiza-tions.Thebuoyanttrajectoriesofthermalwakesafterunderwaterbodiescanbeestimatedbyre-sultshereinpresented.

简介：Amulti-bodycoupleddynamicmodelisdevelopedtosimulatethemotionofaTetheredRemotelyOperatedVehicle(TROV)system.AstrongnonlinearcouplingmotionbetweenumbilicaltetherandROVisdiscussed.ThemovementofROVisconsideredassix-degreesoffreedom.Thelumpedmassmodelisappliedandanaveragedtangentialvectortechniqueisincludedinthethree-dimensionaldynamicresponseequationsofthecable-segments.Themodelcansimulatethethree-dimensionaltransientcoupledmotionofthecomplexmulti-bodysystemintypicalshipmaneuveringconditionsandcanbeusedineitheratowingproblemoratetheredunderwatervehicleproblem.Simulationresultsareseentofitwellwiththeexperiment.