简介:Throughaseriesofmodeltestsoffivescalesfor2-Dfreehydraulicjump,theda-taoffluctuatingpressureactingonthefloorlevelwithinthehydraulicjumpwereobtained.Dur-ingtheexperiments,Froudenumbervariedfrom2.94to8.61,andReynoldsnumberrangedfrom2×10~4to6×10~5.Experimentresultsindicatethattheamplitudescaleoffluctuatingpres-sureisthelengthscaleofmodel,i.e.P’=L,whichagreeswithgravitysimilaritylaw:Thefrequencyscaleofthefluctuatingpressureisaunityi.e.,f=1,whichdoesnotsatisfythegravitysimilaritylaw.
简介:Ageneralstochasticmodeloftheatmosphericpressureattheoceansurfacewasproposed,inwhichthepressurevariationwasrepresentedbyaspectraldecompositionthrougharandomprocessoforthogonalincrements.Fromthebasicequationsofidealandincompressiblefluidasetofperturbationequationsuptosecondorderhadbeenderivedandsolved.Thepressurevariationintheflowfieldhadbeencalculatedusingtheexplicitsolutionsobtained,andwhichdemonstratedaclearrelationbetweentheatmosphericpressureandtheoneatthebottomofdeepocean.Itcanbeseenthatthereisapartofthepressurevariationwhichisnotattenuatingwiththedepth.TheresulthadbeencomparedwiththoseofLonguet-HigginsandKadotaetal.andallpreviousresultsarecontainedinthesolutiongiveninthisartice.Therestrictiononthepreviousworkswithregardtotheprobabilitylawhasbeenremoved,andallconclusionsarededucedwithoutspecificassumptions.Theflexibilityoftheproposedmodelallowsforfurthergeneralizationandextensioninthephysicalaspectsandstatisticaltreatment.
简介:Apre-filtercombinedwiththresholdself-learningwaveletalgorithmisproposedforhydraulicpressuresignalsdenoising.Thedenoisingthresholdisself-learntinthesteadyflowstate,andthenmodifiedunderagivenlimittomakethemeansquareerrorsbetweenreconstructionsignalsanddesirableoutputsminimum,sothecorrespondingoptimaldenoisingthresholdinasingleoperatingcasecanbeobtained.Theseoptimalthresholdsareusedforthewholesignaldenoisingandaredifferentinvariouscases.Simulationresultsandcomparativestudiesshowthatthepresentapproachhasanobviouseffectofnoisesuppressionandissuperiortothoseoftraditionalwaveletalgorithmsandback-propagationneuralnetworks.Italsoprovidestheprecisedataforthenextstepofpipelineleakdetectionusingtransienttechnique.
简介:Basedonthenon-Darcyflowcharacteristicsofsurfactantfloodinginthelowpermeabilityoilfield,consideringthechangesofthresholdpressureandinfluenceofsurfactantonconvection,diffusion,adsorptionandretention,amathematicalmodelisestablishedforathree-dimensional,two-phase,three-componentsurfactantflooding.Anewtreatmentforthechangesofthresholdpressureandanovelcorrectionmethodfortherelativepermeabilitycurveintheprocessofsurfactantfloodingarederived,whichenhancesthematchingdegreebetweenthemathematicalmodelandfieldpractice.ThemathematicalmodelwasusedtoperformthenumericalsimulationstudyforapilottestofsurfactantfloodinginChao45BlockofDaqingOilfield,aproperinjectionplanwasoptimized.Aftertheoptimizedplanwascarriedoutinoilfield,thedesirableeffects,likepressure-reducing,injectionrateincrease,andtheincreaseofoilrecovery,wereachieved.Theaverageoilincreaseforsinglewellreaches37%,theratioofcosttorevenueisabove1:4,sotheeconomiceffectofscaleispromising.
简介:Thetransientflowmathematicalmodelofarbitraryshapedheterogeneousreservoirswithimpermeabilitybarrierisproposedinthispaper.Inordertoestablishthismodel,theperturbationmethodisemployedandthesolutionofmodelisexpandedintoaseriesinpowersofperturbationparameter.ByusingtheBoundaryElementMethod(BEM)andDuhamelprinciple,wellborepressurewitheffectsofskinsandwellborestorageisobtained.Thetypecurvesareplottedandanalyzedconsideringeffectsofheterogeneity,arbitraryshapeandimpermeablebarriers.Finally,theresultsobtainedbyperturbationboundaryelementmethodiscomparedwiththeanalyticalsolutionandisavailableforthetransientpressureanalysisofarbitraryshapedreservoirs.
简介:Thecut-offnegativepressuremethodisoneofeffectiveapproachestosolvetheseepageflowwithfreesurface.Accordingtothecharacteristicsofthismethod,however,ithasbeenfoundoutthatthedeficiencyofthealgorithmsistoeasilycauseinaccuratesimulationinthevicinityoffreesurfaceowingtothepenaltyfunctionwithonlyonecontrollingpenaltyparameter.Therefore,animprovedcut-offpressuremethodwaspresentedbyconstructingpenaltyfunctionwithtwocontrollingpenaltyparameters.Theimprovedalgorithmswereillustratedtobeabletoimprovethesimulationaccuracyandraisetheconvergencespeedthroughconsideringtheeffectsofthepartiallysaturatedorunsaturatedelementsmorereasonablyandcalculatingthenodalexternalforcesmoreaccurately.Finally,theimprovedcut-offnegativepressuremethodwasappliedtothesimulationofunsteadyseepageflowwithfreesurface,andthecorrespondingprogramcodesweredevelopedwithvalidationofsomecases.
简介:Axisymmetricliquidjetshavebeenstudiedextensivelyformorethanonecentury,whilenon-axisymmetricjetsarealsoverycommoninengineeringapplicationsbutattractlessconcern.BasedonEulerianfluid-fluidmodelinFluentsoftware,thisarticleanalysizesthe3-DflowfieldsofpressureatomizerswithV-shapedcutatorifice,whichwillresultinanon-axisymmetricliquidjet.Flowrateanalysisandjetstructureanalysisarecarriedout,theresultsshowthattheflowratecanbeformulatedbyaddingacorrectioncoefficienttotheformulaofinviscidaxisymmetricjetsinatomizationregime,whentheWebernumberislowenoughtomaketheflowfalloutofatomizationregime,andthejetstructuretogetherwiththeflowrateformulawillchange.Analysisshowsthattheevolutionofthesprayandthereforethestructureoftheliquidjetareaffectedmuchbyrelativevelocityandthelocalvolumefractionofliquidphase.
简介:Thisarticleexperimentallyinvestigatedthepressureandcavitationcharacteristicsofhighvelocityflowoverasurfaceirregularitywithandwithoutaerationinanon-circulatingwatertunnelsystem.Thesurfaceirregularityisacylindricalprotrusionmadeofstainlesssteelof6mmdiameterand2mmheight.PressureswithandwithoutaerationweremeasuredwithMPX400Dpressuretransducersandreal-timelyacquiredbyaSINOCERAYE6263dataacquisitionsystem.Variationsinflowregimeswithandwithoutaerationwereobserved.Pressureprofilesandtheirvariationswithairconcentrationupperandlowercylindricalprotrusionontheinvertandobvertwallsweredetermined.Variationsofcavitationnumberwithairconcentrationlowercylindricalprotrusionwereanalyzed.Also,cavitationnumbersinthepresenceandabsenceofaerationwerecompared.
简介:ExperimentalStudyonoil-watertwo-phaseflowpatternsandpressurelosswasconductedonahorizontalsteelpipeloopwith26.1mminnerdiameterand30mtotallength.Theworkingfluidsarewhiteoil,dieseloilandtapwater.Severalinstruments,includinganewtypeofliquid-probearesuccessfullyintegratedtoidentify7differentflowpatterns.Thecharacteristicsoftheflowpatternsandthetransitionprocesswereobservedanddepictedinthispaper.Investigationrevealedthatthepressurelosswasmainlydependedontheflowpatterns.
简介:Inthisarticle,thelowpressureaxialflowfanwithcircumferentialskewedrotorblade,includingtheradialblade,theforward-skewedbladeandthebackward-skewedblade,wasstudiedwithexperimentalmethods.Theaerodynamicperformanceoftherotorswasmeasured.Atthedesignconditionatoutletoftherotors,detailedflowmeasurementswereperformedwithafive-holeprobeandaHot-WireAnemometer(HWA).Theresultsshowthatcomparedtotheradialrotor,theforward-skewedrotordemonstratesawiderStableOperatingRange(SOR),isabletoreducethetotalpressurelossinthehubregionandmakemainloadingofbladeaccumulatinginthemid-spanregion.Thereisawiderwakeintheuppermid-spanregionoftheforward-skewedrotor.Comparedtotheradialrotor,inthebackward-skewedrotorthereishighertotalpressurelossnearthehubandshroudregionsandlowerlossinthemid-spanregion.Inaddition,thevelocitydeficitinthewakeisloweratmid-spanofthebackward-skewedrotorthantheforward-skewedrotor.
简介:Inthepresentpaper,two-andthree-dimensionalvelocitypotentialsgeneratedbypulsatingpressuredistributionsofinfiniteextentonthefreesurfaceofinfinite-depthwatersarestrictlyderivedbasedonspecialcasesofconcentratedpulsatingpressure.Thefar-fieldasymptoticbehaviourofthepotentialsandtheradiationconditionstobesatisfiedbythemarediscussed.Itisprovedinageneralsensethatthepotentialsshouldbecomposedofaforcedwavecomponent,afreewavecomponentandalocaldisturbancecomponent.Theradiationconditionoftheforcedwavecomponentshouldcorrespondtothefar-fieldasymptoticbehaviourofthepressuredistribution,Hence,theformulationofradiationconditionsforthesecond-orderdiffractionpotentialshastheoreticallybecomeclear,Theradiationconditionsfortwo-andthree-dimensionalproblemsareexplicitlygiveninthepaper.
简介:A3-DnumericalformulationisproposedonthehorizontalCartesian,verticalsigma-coordinategridformodelingnon-hydrostaticpressurefree-surfaceflows.Thepressuredecompositiontechniqueandθsemi-implicitmethodareused,withthesolutionprocedurebeingsplitintotwosteps.First,withtheimplicitpartsofnon-hydrostaticpressuresexcluded,theprovisionalvelocityfieldandfreesurfaceareobtainedbysolvinga2-DPoissonequation.Second,thetheoryofthedifferentialoperatorisemployedtoderivethe3-DPoissonequationfornon-hydrostaticpressures,whichissolvedtoobtainthenon-hydrostaticpressuresandtoupdatetheprovisionalvelocityfield.Whenthenon-orthogonalsigma-coordinatetransformationisintroduced,additionaltermscomeintobeing,resultingina15-diagonal,diagonallydominantbutunsymmetriclinearsysteminthe3-DPoissonequationfornon-hydrostaticpressures.TheBiconjugateGradientStabilized(BiCGstab)methodisusedtosolvetheresulting3-Dunsymmetriclinearsysteminsteadoftheconjugategradientmethod,whichcanonlybeusedforsymmetric,positive-definitelinearsystems.Threetestcasesareusedforvalidations.Thesuccessfulsimulationsofthesmall-amplitudewave,asupercriticalflowoverarampandaturbulentflowintheopenchannelindicatethatthenewmodelcansimulatewellnon-hydrostaticflows,supercriticalflowsandturbulentflows.