简介:BasedonTianetal.'stheoreticalmodelofmicrowavescattering,byusingthewindwavespectrumsuggestedbyFungetal.,numericalresultsofpolarizedback-scatteringwerecalculated.Thequantitativerelationshipsbetweenthecalculatedbackscatteringcross-sectionandtheenvironmentalparameters,suchaswindspeeds,azimuthalanglesandincidenceangles,werestudied.Comparedwiththetraditionaltwo-scalescatteringmodel,theresultsaremuchmorecoincidentwiththeobservationsundertheconditionofmoderateincidenceangles,whichisveryusefultomakeupforthetwo-scalemodel.Tomakethenewcalculationmodeltobeusedconvenientlyinthepractice,itssimplifiedformwasproposed.
简介:Thispapergivesemphasisontheresearchoftheproblemoflocalheadlossofcrossfractureflowbyalotofmodelexperiments,andatheoreticalmodeloflocalheadlossofcrossfractureflowisfoundedbyuseofthemomentumlawofwaterflow.Throughthecorrelationanalysisbetweenmodelexperimentalresultsandtheoreticalmodel,thecorrectioncoefficientoftheoreticalmodelisdefinite.Theproposedcalculationformulaoflocalheadlossofcrossfractureflowcanbeusedtoanalyzetheproblemofnetworkfractureseepage.
简介:Thispaperstudiestheflowstructureandthebedloadtransportregimeinbackwaterflows,toprovideatheoreticalsupportforsolvingthesedimenttransportandbedscourproblemsinriversorreservoirswithbackwater.Thebedloadtransportratesunderdifferentconditionsareanalyzedfirstonthebasisoftheoreticalanalysis,measurementcomparisonandflumeexperiment,anditispointedoutthattheexistingformulasforthebedloadtransportratearenotapplicableforthebedloadtransportrateinbackwaterflows.Next,theflowstructureinanon-uniformflowisobservedbyflumeexperiments,andbyintroducingthebackwaterdegreeindex,thequantitativerelationbetweentherelativebedshearstressandthebackwaterdegreeisobtained.Finally,theformulaforthebedloadtransportrateapplicableforthereservoirchannelsegmentwithbackwaterflowsisobtainedthroughmeasurementsandflumeexperiments.
简介:Inthispaper,thehydrodynamiccharacteristicsofwaterflowinChaohuLakearestudiedbyusingthefinitevolumecoastaloceanmodel(FVCOM),whichisverifiedbytheobserveddata.Thetypicalflowfieldandthe3-Dflowstructureareobtainedforthelake.Theflowfieldsunderextremeconditionsareanalyzedtoprovideaprospectiveknowledgeofthewaterexchangeandthetransportprocess.Theinfluenceofthewindontheflowisdeterminedbythecrossspectrummethod.Theresultsshowthatthewind-drivenflowdominatesmostareaofthelake.Underprevailingwindsinsummerandwinter,thewaterflowstowardsthedownwindsideattheupperlayerwhiletowardstheupwindsideatthelowerlayerinmostareaexceptthataroundtheChaohuSluice.Theextremewindspeedisnotfavorableforthewaterexchangewhilethesluice’sreleasingwateracceleratestheprocess.Thewatervelocityinthelakeiscloselyrelatedwiththewindspeed.
简介:Duetotheinteractionbetweenthemainhullandsidehulls,differentlayoutsandlengthsofsidehullsaffectthewaveloadssignificantly.Basedonthree-dimensionalpotentialtheoryandGreen'sfunction,thisarticlegivesthesignificantvaluesforwaveloads,includingverticalshearforcesandverticalbendingmomentsatdifferentlocationsonthemainhull,andtransversebendingmomentsatthejunctionofthecrossstructureandmainhull.Inaddition,aparametricoptimizationofwaveloadsfordifferentlayoutsandlengthsofsidehullswereperfomed.Severalspeedsandwaveheadingswerealsoconsidered.Finally,spectralanalysiswasconductedtoattainloaddistribution.Theconclusionsofthisstudyareconducivetothedesignandoptimizationofthisnewtypeofship.
简介:Thedragreductionofcompliantsurfaceisstudiedinashipmodeltank.There-sultsofthemeasureddragofaflatplatemodelshowthatthecompliantsurfaceiscapableofre-ducingdraginacertainrangeofspeeds,Themaximumdragreductionis15.7%whenthecom-pliantsurfaceismerelyontheonesideoftheplate.Theseresultshaveconfirmedthepredictedcharacteristicsofcompliantsurfaces.
简介:Chinabearsahighreliefinthewestandlowintheeast,withcomplextopography,totaling2/3ofthewholecountry'sareaformountains,hillyregionsandzigzagplateaus.Thereforethehydraulicresourcesareabundant,withpotentialhydraulicamountofabout680000MW,ofwhich,smallhydropowerresourceisveryrichtooandhasgreatexploitablepotential.Accordingtogeneralinvestigationinearly1980s,theexploitableamountreached87000MW,rankingthetopintheworld.
简介:Amulti-functionsamplingsystemhasbeensetupinShanghaiShip&ShippingResearchInstitute(SSSRI)whereatestonthefluctuatingpressureoftwopropellermodelswerecarriedout.Thispaperdealswithastudyonthetechnicalproblemsconcerningthemeasurementandanalysistechniquesinvolvedinthetest.Thesamplingandprocessingprocedureofsignalisoneofthemajorfactorsaffectingtheac-curacyandstabilityofthepredictionoffluctuatingpressureinducedbypropeller.Integral-peri-odsampling,highenoughsamplingfrequencyandsuitableresolutionmustbekeptinsamplingandprocessing.Theprocedureofsamplingandprocessingshouldbevalidatedbystandardsignalcorrespondingtothebladefrequencyofdifferentordersincomparativetests.
简介:TheTangjiashanlandslidedamfailedonJune10,2008,whichwasthelargestoneformedduringtheWenchuanearthquakeinChina.Nohumanliveswerelostinthisdamfailure.Thispaperpresentsadescriptionofthedam,includingthedamgeometry,thehydrographandthereservoircapacity,thediversionchannelandthedrainagefromthelake.Severalempiricalmodelsareappliedtopredictthebreachparameters,thepeakoutflowsandthereservoirvolumesduringthisbreachevent.Themainobjectiveofthestudyistocomparevariouspredictionmodelsandtomakerecommendationofthebestmodelforthepredictionofthebreachwidth,thefailuretime,andthepeakoutflow.ThebreachwidthspredictedbytheFroehlichmethodswithconsiderationsofthereservoirstoragesandtheeffectoffailuremodeareconsideredtobemorereasonable.Allpredictionmethodsdiscussedinthispaperarefoundtounderestimatethebreachformationtimeduetothecomplexmaterialandthelargethicknessofthedam.Theresultsfromthesoilconservationservices(SCS)methodcomparewellwiththeobservedpeakoutflow.TheMaronemethodincombinationwiththecoefficientexpressionsproposedbyMacchionegivesexcellentresultsinthesimulationofthereservoirvolume-levelcurve.
简介:Aninvestigationoftheventilatedsupercavitationforasupercavitatingvehiclepitchingupanddowninthesupercavitywascarriedoutinahigh-speedwatertunnel.Theemphasisislaidontheunderstandingoftheinteractionofthevehicleaftbodywiththecavityboundary.Theflowcharacteristicsweremeasuredandthestabilityofsupercavitingflowwithdifferentpitchingfrequenciesandamplitudeswasanalyzed.Inparticular,theobjectivesofthisstudyaretounderstandtheeffectoftheimpactuponthecavitydistortion,andtoquantifytheimpactprocessbyinvestigatingtheevolutionofthepressureinsidethecavityandthentheloadsonthevehicleduringthepitchingmotion.Itisalsoshownthattheevolutionofthepressuredetectedindifferent,asinsidethesupercavity,iscoherentanduniformduringtheperiodsofthepitchingmotion.Thisstudyisofdirectrelevancetoreliableandaccuratepredictionofhydrodynamicloadsassociatedwiththeslammingandimpactonsupercavitatingvehicles.
简介:AnexperimentalapparatustoinvestigateACMHDpumpwasestablished,whichmainlyconsistsofarotarypermanentmagnetwith4polesanannularchannel,amotor,ashaftandaplatform.Themagnetgeneratesafieldsimilartosinusoidwiththemaximumof0.9TinthechannelwhenitisrotatedupbythemotortosimulateanACmagneticfield.Thismovingmagneticfieldactsontheconductivefluidinthechannel,andproducesanelectromagneticforcetomovethefluidinthesamedirectionasthatofthemagnetrotating.Experimentswerecarriedouttoinvestigatetheperformanceofthepump.Flowvelocityintheannularchannelwasmeasuredfordifferentconductivitiesandrotatingspeedsofthemagnet.Theresultsshowthattheflowrateandpressureincreaseasthemagneticfieldstrength,fluidconductivityandfrequencyofthemagneticfieldincrease.
简介:Particleimpactdrillingisanefficientdrillingtechnologyfordeep-wellhardformation,Withthistechnology,therockiscutmainlybyhigh-speedsphericalparticleimpactunderhydraulicaction.Inthisarticle,theinfluenceofjetflowfactors,hydraulicfactorsandabrasivefactorsonrockbreakingisstudiedthroughindoorexperimentsofimpactbysteelparticles.Theresultsindicatethattheparticlewaterjethasanoptimalstandoffdistanceandparticleconcentration;therockbreakingeffectdeclineswiththeincreaseoftheconfiningpressureandthedecreaseofthepumppressureandparticlediameter.Thisstudywillprovidesomefoodofthoughtforthedevelopmentofparticleimpactdrillingtechnology.
简介:Thehydraulicandsedimentdepositionproblemsinthewaterintakesystemofapumpinghousewerestudiedbyphysicalmodel.Theexperimentalresultsofdifferentworkingcasesindicatethatthesedimentdepositionsatthegates,stillingbasinandculvertsareveryfewwhenthesystemwasnormallyoperated,butintheforebayofpumpinghouse,especiallyinthepumpinghouseforlivingwater,theamountofsedimentdepositionsometimesisconsiderablylarge.Atthefrontoftheentryofpumpinghouseforlivingwater,installingasetofobliquepipescanpreventthecoarsegrainstoenterit,thedepositionamountwillobviouslydecrease.
简介:NUMERICALSTUDYOFTURBULENTJETSCONFINEDBETWEENTWOCONCENTRICSPHERESZhangGuang-hua;TangGe-feng(TsinghuaUniversity,Beijing,100084,...
简介:TheproblemofacreepingflowofNewtonianfluidextrudedfromaplaneslitoracircularpipe.intheabsenceofgravity,issimulatedsuccessfullybyusingthecontinuous-pressure-elementmethod,thediscontinuous-pressure-elementmethod,theconsistantpenaltymethod,thereducedintegrationpenaltymethodandthemodifiedreducedintegrationpenaltymethodproposedbyOden.Throughcomparisonsbetweenthesemethods,itisconvincedthatthediscontinuous-pressureinterpolationschemesresultinmoreaccuratemassconservationand,consequently,morerapidconvergenceofthefree-surfaceiterationthanthecontinuousonedoes.Thereducedintegrationpenaltymethodcanfurtherreducethecostofcomputationwhileretainingsufficientaccuracyofthesolution.