简介:Inthepresentwork,computationalsimulationswasmadeusingANSYSCFXtopredicttheimprovementsinfilmcoolingperformancewithdualtrench.Dual-trenchconfigurationconsistsoftwotrenchestogether,onewidertrenchandtheotherisnarrowtrenchthatextrudedfromthewiderone.Severalblowingratiosintherange(0.5:5)wereinvestigated.Thepitch-to-diameterratioof2.775isused.Byusingthedualtrenchconfiguration,thecoolantjetimpactedthetrenchwalltwotimesallowingincreasingthespreadingofcoolantlaterallyinthetrench,reducingjetvelocityandjetcompletelycoveredonthesurface.Theresultsindicatethatthisconfigurationincreasedadiabaticeffectivenessasblowingratioincreased.Thespatiallyaveragedadiabaticeffectivenessreached57.6%foratM=2.Noobservedfilmblow-offatallblowingratios.Theadiabaticfilmeffectivenessofdualtrenchcaseoutperformedthenarrowtrenchcase,laidbackfan-shapedhole,fan-shapedholeandcylinderholeatdifferentblowingratios.
简介:Thescatteringprobleminvolvingwaterwavesbysmallundulationontheporousocean-bedinatwo-layerfluid,isinvestigatedwithintheframeworkofthetwo-dimensionallinearwaterwavetheorywheretheupperlayeriscoveredbyathinuniformsheetoficemodeledasathinelasticplate.Insuchatwo-layerfluidthereexistwaveswithtwodifferentmodes,onewithalowerwavenumberpropagatealongtheice-coverwhilstthosewithahigherwavenumberpropagatealongtheinterface.Anincidentwaveofaparticularwavenumbergetsreflectedandtransmittedoverthebottomundulationintowavesofbothmodes.PerturbationanalysisinconjunctionwiththeFouriertransformtechniqueisusedtoderivethefirst-ordercorrectionsofreflectionandtransmissioncoefficientsforboththemodesduetoincidentwavesoftwodifferentmodes.Onespecialtypeofbottomtopographyisconsideredasanexampletoevaluatetherelatedcoefficientsindetail.Thesecoefficientsaredepictedingraphicalformstodemonstratethetransformationofwaveenergybetweenthetwomodesandalsotoillustratetheeffectsoftheicesheetandtheporosityoftheundulatingbed.
简介:Severalindustrialapplicationssuchaselectronicdevices,heatexchangers,gasturbineblades,etc.needcoolingprocesses.Theinternalcoolingtechniqueisproperforsomeapplications.Inthepresentwork,computationalsimulationsweremadeusingANSYSCFXtopredicttheimprovementsofinternalheattransferintherectangularribbedchannelusingdifferentcoolants.Severalcoolantssuchasair,steam,air/mistandsteam/mistwereinvestigated.Theshearstresstransportmodel(SST)isselectedbycomparingthestandardk-ωandOmegaReynoldsStress(ωRS)turbulencemodelswithexperimentalresults.Theresultsindicatethattheheattransfercoefficientsareenhancedintheribbedchannelwhileinjectingsmallamountsofmist.Theheattransfercoefficientsofair/mist,steamandsteam/mistincreaseby12.5%,49.5%and107%overthatofair,respectively.Furthermore,incomparisontoair,theair/mistheattransfercoefficientenhancesbyabout1.05to1.14timeswhenthemistmassfractionincreasesfrom2%to8%,respectively.Thesteam/mistheattransfercoefficientincreasesbyabout1.12to1.27timeshigherthanthatofsteamovertheconsideredrangeofmistmassfraction.
简介:Themainchallengeforcontainerportsistheplanningrequiredforberthingcontainershipswhiledockedinport.Growthofcontainerizationiscreatingproblemsforportsandcontainerterminalsastheyreachtheircapacitylimitsofvariousresourceswhichincreasinglyleadstotrafficandportcongestion.Goodplanningandmanagementofcontainerterminaloperationsreduceswaitingtimeforlinerships.Reducingthewaitingtimeimprovestheterminal’sproductivityanddecreasestheportdifficulties.Twoimportantkeystoreducingwaitingtimewithberthallocationaredeterminingsuitableaccesschanneldepthsandincreasingthenumberofberthswhichinthispaperarestudiedandanalyzedaspracticalsolutions.Simulationbasedanalysisistheonlywaytounderstandhowvariousresourcesinteractwitheachotherandhowtheyareaffectedintheberthingtimeofships.WeusedtheEnterpriseDynamicssoftwaretoproducesimulationmodelsduetothecomplexityandnatureoftheproblems.WefurtherpresentcasestudyforberthallocationsimulationofthebiggestcontainerterminalinIranandtheoptimumaccesschanneldepthandthenumberofberthsareobtainedfromsimulationresults.Theresultsshowasignificantreductioninthewaitingtimeforcontainershipsandcanbeusefulformajorfunctionsinoperationsanddevelopmentofcontainershipterminals.
简介:Inordertostudycavitationcharacteristicsofa2-Dhydrofoil,themethodthatcombinesnonlinearcavitationmodelandmixed-iterationisusedtopredictandanalyzethecavitationperformanceofhydrofoils.ThecavitationelementsarenonlinearlydisposedbasedontheGreenformulaandperturbationpotentialpanelmethod.Atthesametime,themethodthatcombinescavityshapeforfixedcavitylength(CSCL)iterationandcavityshapeforfixedcavitationnumber(CSCN)iterationisusedtoworkoutthethicknessandlengthofhydrofoilcavitations.Throughanalysisofcalculationresults,itcanbeconcludedthatthejumpofpressureandvelocitypotentiallyexistbetweencavitationendareaandnon-cavitationsareaonsuctionsurfacewhencavitationoccursonhydrofoil.Incertainanglesofattack,thecavitationnumberhasanegativeimpactonthelengthofcavitations.Andunderthesameangleofattackandcavitationnumber,thebiggerthethicknessofthehydrofoil,theshorterthecavitationslength.
简介:文章阐明了PBL教学法在“船舶强度与结构设计”课程教学中的应用,介绍了其具体实施步骤。实施效果显示,该方法取得了良好的教学效果,具有一定的参考意义。
简介:TheobjectiveofthisresearchwastoexamineifcertainstrainsofBacillusbacteria,couldsurviveindrypowderproductsandifso,couldthebacteriadegradeorganiccontaminantsinsalinewastewateronaship.Aspartofthestudy,weisolated7domesticatedstrainsnamedNY1,NY2,…,andNY7,thestrainNY6showedtohavethebestperformancefororganicmatterdegradationandcouldsurviveindrypowdermorethan3months.NY6wasidentifiedasBacillusaerius,basedonthemorphologicalandphysic-chemicalproperties.Itsoptimalgrowthconditionswereasfollows:salinitywas2%;temperaturewas37℃;pHwasin6.5-7.0;bestratioofC:N:Pwas100:5:1.ThecapabilityofitsdrypowderforChemicalOxygenDemand(COD)removalwas800mgCOD/ginsynthesizedmarinewastewaterwith2%salinity.Thesporesinthedrypowderwere1.972×108g-1.
简介:Inthenormaloperationcondition,aconventionalsquare-rootcubatureKalmanfilter(SRCKF)givessufficientlygoodestimationresults.However,ifthemeasurementsarenotreliable,theSRCKFmaygiveinaccurateresultsanddivergesbytime.ThisstudyintroducesanadaptiveSRCKFalgorithmwiththefiltergaincorrectionforthecaseofmeasurementmalfunctions.Byproposingaswitchingcriterion,anoptimalfilterisselectedfromtheadaptiveandconventionalSRCKFaccordingtothemeasurementquality.Asubsystemsoftfaultdetectionalgorithmisbuiltwiththefilterresidual.Utilizingaclearsubsystemfaultcoefficient,thefaultysubsystemisisolatedasaresultofthesystemreconstruction.Inordertoimprovetheperformanceofthemulti-sensorsystem,ahybridfusionalgorithmispresentedbasedontheadaptiveSRCKF.Thestateanderrorcovariancematrixarealsopredictedbythepriorifusionestimates,andareupdatedbythepredictedandestimatedinformationofsubsystems.Theproposedalgorithmswereappliedtothevesseldynamicpositioningsystemsimulation.TheywerecomparedwithnormalSRCKFandlocalestimationweightedfusionalgorithm.ThesimulationresultsshowthatthepresentedadaptiveSRCKFimprovestherobustnessofsubsystemfiltering,andthehybridfusionalgorithmhasthebetterperformance.Thesimulationverifiestheeffectivenessoftheproposedalgorithms.
简介:文章概述了STCW公约马尼拉修正案对航海技术专业修改的主要内容及影响,并从实践教学出发.分析了现阶段高职航海技术专业实践教学中师资队伍、教学实训设备、教学内容等方面存在的问题,提出了相应对策和建议.以期为履约过程中全面的教学改革提供思路。
简介:文中在介绍我国目前在海上油污事故赔偿方面的立法状况的基础上,分析了我国目前立法中存在的问题,进而指出中国未来加入《基金公约》的合理性以及从国际公约中借鉴相关标准制定专门的海上油污单行立法的必要性.