简介：Basedontheanalysisoftheaveragedaxisymmetricturbulentflowandthemotionandgrowthofgasnucleiintheflow,thispaperpresentsamethodforpredictingcavitationin-ceptioninpipelines.MathematicmodelisproposedandthefluctuatingpressureintheflowandotherrandomfactorswithrespecttogasnucleiaretreatedusingtheMonte-Carlomethod.Sothatthebridgebetweenmacroscopicaspectofcavitationintheflowandthemicroscopiceventofindividualnucleuscavitationissetup.Numericalinvestigationandexperimnentaltestarecarriedoutfortheflowpastanorificeinauniformpipewithcircularsection.

简介：Thechangesofthedevelopingturbulentflowcharacteristicsincurvedductafteraddingabafflearestudiednumericallyatthebody-fittedcoordinates.ak-εmodelisusedtorepresenttheturbulence.acurvedductofrectangularcross-sectioniscomputedfirstly,ithasbeenobservedthatthepredictionsusingtheprocedureagreeverysatisfactorywiththeexperimentaldata.Then,twokindsofsquareductsarestudied,oneisnormalcurvedduct,theotherisaductwithabaffle.Thecomputationalresultsarepresentedandcomparedtoeachother,inordertodisplaythechangesoftheflowafteraddingabaffleincurvedducts.Thesecondaryflowinaductwithabaffleischaracterizedbyfour-vorticesstructurewiththeoutertwobiggerthantheinnertwo.Besides,comparedwiththeductwithoutabaffle,theintensityofthesecondaryflowsisreduced,whichresultsintheflowfieldofthecross-sectionmuchmoreequableandhasmuchmoresignificantmeaningintheengineering.

简介：Sincetrimandsinkagearesignificantwhilevesselsareadvancingforwardwithhighspeed,thepredictedvesselresistancebasedonrestrainedmodeltheoryorexperimentmaynotberealresistanceofvesselsduringvoyage.Itisnecessarytotaketheinfluenceofhullgestureintoaccountfororedictingtheresistanceofhigh-speedship.Inthepresentworktheresistanceproblemofhighspeedshipistreatedwiththeviscousflowtheory,andthedynamicmeshtechniqueisadoptedtocoincidewithvariationofhullgestureofhighspeedvesselonvoyage.ThesimulationofthemodelsofS60shipandatrimaranmovingintowingtankwithhighspeedareconductedbyusingtheabovetheoryandtechnique.Thecorrespondingnumericalresultsareingoodagreementwiththeexperimentaldata.Itindicatesthattheresistancepredictionforhighspeedvesselsshouldtakehullgestureintoconsiderationandthedynamicmeshmethodproposedhereiseffectiveincalculatingtheresistanceofhighspeedvessels.

简介：ＵＮＳＴＥＡＤＹＰＲＯＰＥＬＬＥＲＳＵＲＦＡＣＥＰＲＥＤＩＣＴＩＯＮＷＩＴＨＡＰＯＴＥＮＴＩＡＬＢＡＳＥＤＰＡＮＥＬＭＥＴＨＯＤ￥ＣｈｅｎＪｉａ－ｄｏｎｇ（ＣｈｉｎａＳｈｉｐＳｃｉｅｎｔｉｆｉｃＲｅｓｅａｒｃｈＣｅｎｔｅｒ，Ｂｏｘ１１６，Ｗｕｘｉ２１...

简介：Thispaperhaspredictedtherangeandvolumeofunsteadysheetcavitationofapropellerbyusingthesurfacepanelmethod.Thelinearizationincavitythicknessisadoptedtoreducethecomputingtimeandstoragespace.Theiterationschemebetweenchordwisestripshasbeenusedbecausetherangeandvolumeofcavitationarebothunknown.Thepropellercavitationrangedeterminedbythecalculationmethodpresentedinthispaperagreeswiththeobservationresultsofcavityimageatcavitationtunnelverywell,andthisprovesthepracticabilityofthemethod.

简介：Theunsteadysheetcavitationofpoddedpropellerwaspredictedbyusingasurfacepanelmethod.Theinteractionbetweenpropellerandpodwastreatedwiththeiterativecalculationofinducedvelocitypotential,andthemethodofinducedvelocitypotentialcansaveagreatdealofstorageandcomputationtimecomparedtothemethodofinducedvelocity.Theinducedvelocitypotentialofunitsingularityoneverypodpaneltoeverykeybladepanelandofunitsingularityoneverykeybladepanelanditswakepaneltoeverypodpanelwerecalculatedwhenthekeybladeisateveryangleposition.Basedonthewakemodeloftheconventionalsinglepropeller,anewwakemodelofpoddedpropellerwasconstructed.Thepropellerisanalyzedonlyonthekeybladeinordertosavecomputationtimeandmemoryspace.Themethodcanbeusedtocalculatethehydrodynamicsperformanceandcavitationofpropellerinuniformandnon-uniforminflows.Itcangivetheunsteadyforceandcavitationshapeofpropeller.Thepropellercavitationrangedeterminedbythepresentmethodagreeswiththeobservationresultsofcavityimagegivenincavitationtunnelwell,andthisprovesthepracticabilityofthemethod.

简介：Thewatertemperaturestratificationinlargereservoirsmighthaveseriousecologicalandenvironmentalconsequences.Themodelingofthetemperaturedistributionanditshistoryisofgreatimportancebothforstudyingtheunderlyingmechanismsandforcontrollingtheadverseeffects.Todevelopaneffectiveandefficientmethodforsimulationoftemporalandspatialtemperaturevariations,alatticeBoltzmannmethod(LBM)modelfor3-Dthermalbuoyancyflowsisproposedandvalidatedbythetemperaturedatameasuredinamodelreservoir.ThispaperdiscussesimportantaspectsoftheLBManditsturbulencemodel,analyzesthegravitysinkingmechanismofcoldcurrents,anddemonstratesthecomplexityofthetemperatureredistributionprocess.Goodagreementbetweenthesimulatedandmeasuredresultsshowsthatthenewlydevelopedmethodisfeasibleandpowerful,anditwillbeusedforthewatertemperaturepredictioninactualreservoirsinanearfuture.

简介：Physicalmodeltestswerecounductedtopredictlocalscourandmaximumscourdeptharoundthelargediametercylinderslocatedinthe(sand)seabedundertheactionofbothwaveandcurrent.Accordingtotheresultoftests,ananalysiswasmadeonallthefactorsinfluencingthescour.Theresultsshowsthatfortheseabedwithrelativefinegrainsinshallowwater(0.07＜h/L≤0.28),whentherelativediameterD/Lofthecylinderiswithin0.3-0.7,themaineffectivescourfactorsaroundthecylinderintheseabedarediameterDofthecylinder,thewaveheightH,thewavelengthL,thevelocityVcofthecurrentandtheparametersrelatedtotheseabedsoiltexture.Themainparametersinfluecingthemaximumscourdepthwereanalyzed,andthetestdataweresyntherized,toobtaintheformulapredictingthescourdeptharoundthelargediametercylinderundertheofbothwaveandcurrent.