简介:ThispaperdescribesanewphenomenonofacousticstreamingwhichtakesplacewhenaHelmholtzresonatorisexcitedbyaninsidesoundsourcewithresonantfrequency,andtakestheformofastrongturbulentjet.Theflowvisualizations,hotwireandLDVmeasurementsarecombinedtoinvestigatetheprocessofacousticstreaming.ItisfoundthatthiskindofacousticstreamingresultsfromthecontributionofReynoldsstress.
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简介:Inthispaper,thephenomenononcollapsibletubedisplacementoscillation,anewbehaviorofthecollapsibletubepuisatileflowhasbeenstudied.Theexperimentsshowthatthecollapsibletube,inwhichtheflowisperiodicpuisatileintheupstream,willoscillateasasimplesupportedbeamwhenitiscollapsedtocertainextent,andthatifthetubeiscollapsedcontinue,thisoscillationwilltendtoweakandcompletelydisappearlastly.Ananalyticalmodelcorrespondingtothecollapsibletubedisplacementoscillationanditsgovernedequationsaresetupfromtheexperimentbackground.Byanalysingthemodelandsolvingtheequations,thecollapsibletubedisplacementoscillationpatternandtheoscillationoccurringordisappearingcriterionareobtained.Theresultspredictedbythisstudyareinagreementwiththoseobservedfromexperimentphenomena.
简介:Tostudythemechanicalpropertiesofthefilm/substratestructure,thefiniteelementcodeABAQUSv6.9-1isadoptedtosimulatethetensilemechanicalbehaviorofthenanoscalethinfilmbondedtoasubstrate.Thebifurcationphenomenonofthestructureunderuniaxialtensionisfound:thesingle-neckdeformation,themultiple-neckdeformationandtheuniformdeformation.Thesubstrateandthefilmareregardedaspower-hardeningmaterialsobeyingtheJ2deformationtheory.Firstly,theinfluenceofmaterialhardeningmatchontensilebifurcationmodeisanalyzedunderperfectlywell-bondedinterfacecondition.Then,theeffectsofinterfacialstiffnessandothersuperficialdefectssurroundingtheimperfectiononbifurcationmodeareinvestigated.Itisconcludedthatunderthewell-bondedinterfacecondition,ifthestressofthesubstrateislargerthanthefilm,thefilmwilluniformlydeformwiththesubstrate;ifthestressofthesubstrateissmallerthanthefilm,thefilmwillformasingleneck,exceptthecasethataweakly-hardeningfilmisbondedtoasteeply-hardeningsubstratewhenmultipleneckscanbeformed.Withthedecreaseofinterfacialstiffness,theuniformdeformationmodecantransformintothemultiple-neckdeformationmode,andfurthertransformintothesingle-neckdeformationmode.Andotherdefectssurroundingtheimperfectioncaninfluencethewavelengthofdeformationandnecknumber.
简介:Inthisstudy,thenull-fieldboundaryintegralequationmethod(BIEM)andtheimagemethodareusedtosolvetheSHwavescatteringproblemcontainingsemi-circularcanyonsandcirculartunnels.Tofullyutilizetheanalyticalpropertyofcirculargeometry,thepolarcoordinatesareusedtoexpandtheclosed-formfundamentalsolutiontothedegeneratekernel,andtheFourierseriesisalsointroducedtorepresenttheboundarydensity.Bycollocatingboundarypointstomatchboundaryconditionontheboundary,alinearalgebraicsystemisconstructed.Theunknowncoefficientsinthealgebraicsystemcanbeeasilydetermined.Inthisway,asemi-analyticalapproachisdeveloped.Followingtheexperienceofnear-trappedmodesinwaterwaveproblemsofthefullplane,thefocusingphenomenonandnear-trappedmodesfortheSHwaveproblemofthehalf-planearesolved,sincethetwoproblemsobeythesamemathematicalmodel.Inthisstudy,itisfoundthattheSHwaveproblemcontainingtwosemi-circularcanyonsandacirculartunnelhasthenear-trappedmodeandthefocusingphenomenonforaspecialincidentangleandwavenumber.Inthissituation,theamplificationfactorfortheamplitudeofdisplacementisover300.
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简介:Fingeringphenomenaarecommonoccurrenceinthenaturalworld.Itgenerallytakesplacewhenalessviscousfluiddisplacesamoreviscousfluidtypicallyinporousmedia.Nowadays,suchphenomenahaveextensivelybeenstudiedduetoitsimportanceinmanyindustrialfields.Inthispaper,theeffectsofsurfacewettabilityonfingerpatternarestudiedandsimulatednumericallybytheLatticeBoltzmannmethod(LBM).Thedisplacementefficiencyisinvestigatedbyusingtwoparameters,namely,thebreakthroughtimeandthearealsweepefficiency.Thesimulationhasdemonstratedthatsurfacewettabilitywillinfluencethefingerpatternnomatterthegravityisconsideredornot,butinthepresenceofgravity,thefingerpatternismuchmorecomplicatedandirregularduetothecoexistenceandcompetitionofcapillaryforce,viscousforceandgravity.