简介：Thenatureofthethree-dimensionaltransitionarisingintheflowpastacylinderisinvestigatedbyapplyingtheLifschitz-HameiritheoryalongspecialLagrangiantrajectoriesexistinginitswake.ResultsshowthatthevonKarmanstreetisunstablewithregardtoshort-wavelengthperturbations.Theasymptoticanalysispredictsthepossibleexistenceofbothsynchronous(asmodesAandB)andasynchronous(asmodeC)instabilities,eachassociatedtospecificLagrangianorbits.Theproposedstudyprovidesusefulqualitativeinformationontheoriginofthedifferentmodesbutnoquantitativeagreementbetweenthegrowthratespredictedbytheasymptoticanalysisandbyaglobalstabilityanalysisisobserved.Thereasonsforsuchmismatcharebrieflydiscussedandpossibleimprovementstothepresentanalysisaresuggested.

简介：Thephysicalmechanismforgenerationofstreamwisevortices(orribvortices)inthecylinderwakeisnumericallyinvestigatedwithafinite-differencescheme.Rayleigh’stheoryofcentrifugalinstabilityforinviscidaxisymmetricflowisextendedtoanalyzethe2-Dprimaryflows.Accordingly,ananalyticaldimensionlessgroupRay=-(r/vθ)■vθ/■r-1isderived,wherevθrepresentsthevelocityofafluidelementrelativetotheoncomingflow,risthelocalcurvatureradiusoftheelementpathline.CentrifugalinstabilityoccurswhenRay>0.StabilityanalysesarecarriedoutwiththisdiscriminantforprimaryflowsatdifferenttimelevelsinahalfsheddingperiodofthevonKarman(orvK)vortices.UnstableareasareidentifiedandthelocationsofribvorticesarecoincidentwellwiththeunstableareaswithinthefirstwavelengthofvKvorticesbehindthecylinder.Thenumericalresultsalsoshowthatribvorticesexperienceamplificationinthisregion.Itisapparentthatcentrifugalinstabilityplaysanimportantroleinthegenerationofribvorticesinthecylinderwake.

简介：FlowfieldsaroundarotatingcircularcylinderinauniformstreamarecomputedusingalowdimensionalGalerkinmethod.ResultsshowthattheformationofaFopplevortexpairbehindastationarycircularcylinderiscausedbythestructuralinstabilityinthevicinityofthesaddlelocatedattherearofthecylinder.Forrotatingcylinderabifurcationdiagramwiththeconsiderationoftwoparameters,ReynoldsnumberReandrotationparameterα,isbuiltbyakinematicanalysisofthesteadyflowfields.

简介：Theinertiasofthefluidandtheinnercylinderincoaxialcylinderrheometer(CACR)havegreatinfluenceontheunsteadyflowofnon-Newtonianfluid.EvenfortheNewtonianfluidthereexistthesocalled'stressovershoot'phenomenon.Inthepresentarticlethisphenomenonwasstudiedindetailandamethodcorrectingthemeasuredresultsforanunsteadyflowintherheometerwasproposed.Itisfoundthattheinertiaeffectofthefluidcanbeignoredwhenthegapbetweencylindersissmall.

简介：Corioliseffectisconsideredintheanalysisofarotatingpiezoelectrichollowcylinder.AninhomogeneousBesselequationgoverningtheradialmechanicaldisplacementisderived,whichcanbeapproximatedasanEulertypedifferentialequationwhenthecylinderisverythin.NumericalexamplesshowthattheCorioliseffectcanbesignificantundercertainconditions.

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简介：Inordertoinvestigatethescaleefectofturbulentflowaroundacircularcylinder,twosimilaritynumbers(criteria)basedonturbulentkineticanddissipationratesassociatedwiththefluctuationcharacteristicsofturbulencewakearededucedbyanalyzingtheReynoldsaveragedNavier–Stokesequations(RANS).TheRNGk–εmodelsandfinitevolumemethodareusedtosolvethegoverningequationsandthesecond-orderimplicittimeandupwindspacediscretizationalgorithmsareusedtodiscretethegoverningequations.Anumericalcomputationofflowparametersaroundatwo-dimensionalcircularcylinderwithReynoldsnumbersrangingfrom102to107isaccomplishedandtheresultindicatesthatthefluctuationofturbulenceflowalongthecenterlineinthewakeofcircularcylindercanneverbechangedwithincreasingReynoldsnumberswhenRe3×106.Thisconclusionisusefulforcontrollingthescaleofnumericalcalculationsandforapplyingmodeltestdatatoengineeringpractice.

简介：Theequationofstressintensityfactors(SIF)ofinternallypressurizedthick-walledcylinderwasusedasthereferencecase.SIFequationofrotatingthick-walledcylindercontainingaradialcrackalongtheinternalborewaspresentedinweightfunctionmethod.Theweightfumctionformulaswereworkedoutandcanbeusedforallkindsofdepthofcracks,rotatingspeed,material,sizeofthick-walledcylindertocalculatethestressintensityfactors.Theresultsindicatedthevalidityandeffectivenessoftheseformulas.Meanwhile,therulesofthestressintensityfactorsinrotatingthick-walledcylinderwiththechangeofcrackdepthsandtheratioofouterradiustoinnerradiuswerestudied.Thestudiesarevaluabletoengineeringapplication.

简介：为semilinear的起始边界的值问题的答案的空间腐烂在易于侧面的边界上的零个条件的可变剖面图的半无限的柱体的寓言的方程被调查。秒顺序显示出空间腐烂O的微分不平等(exp(z2/(4(t+t0))))为L2p，答案的代表性的措施被获得。导致生长或腐烂的一阶的微分不平等也被导出。在生长的情况中，为在空间的发作的上面的界限被获得，当在腐烂的情况中为全部的精力的上面的界限以数据被获得时。

简介：经过有几何骚乱的方形节的柱体的流动被数字模拟调查。额外的条款，由于印射转变模仿的介绍，进转变Navier的骚乱的效果司烧方程，是正确地发源，并且在以前的文学的不正确的被指出并且分析。而且，在涡度之间的关系特别在柱体表面上，并且骚乱理论上被导出并且解释。计算与另一个目的在0.006，0.025和0.167的起浪的100和180和三个振幅的二个雷纳兹数字被执行在身体上在wake和力量在旋涡动力学上探索不同雷纳兹数字和骚乱的效果。数字结果证明了在0.025的温和起浪，流的Kármán旋涡为Re=完全被压制100，当强迫的旋涡脱臼被显得在时近在180的雷纳兹数字醒来。drag减小在Re=直到21.6%100和25.7%在Re=180为0.167的高起浪与非起浪的柱体相比。电梯和与不同雷纳兹数字和波浪险峻改变的Strouhal数字也被获得。

简介：AtheoreticalanalysisontheelectricdoublelayerformednearthesurfaceofaninfinitecylinderwithanellipticalcrosssectionandaprescribedelectricpotentialinanionicconductorwasperformedusingthelinearizedGouy–Chapmantheory.Asemi-analyticalsolutionintermsoftheMathieufunctionswasobtained.Thedistributionsoftheelectricpotential,cations,anions,andelectricfieldwerecalculated.Theeffectsofvariousphysicalandgeometricparameterswereexamined.Thefieldsvaryrapidlyneartheellipticalboundaryandarenearlyuniformatfarfield.Electricfieldconcentrationswerefoundattheendsofthesemi-majorandsemi-minoraxesoftheellipse.Theseconcentrationsaresensitivetothephysicalandgeometricparameters.

简介：DetaileddistributionsofheatfluxintheregionofshockwaveandturbulentboundarylayerinteractioninducedbyacylinderweremeasuredintheshocktunnelOilflowpatternsandSchlierenphoto-graphsweretaken.Empiricalrelationsweregivenfordeterminingseparationshockangle,peaksofheatfluxandtheirlocationsonbothcylinderleadingedgeandflatplatesurface,andothercharacteristicparametersoftheinteractionregion.

简介：WestudyamodifiedversionoftheLane-Emdenequationofthesecondkindmodellingathermalexplosioninaninfinitecylinderandasphere.Wefirstshowthatthesolutiontotherelevantboundaryvalueproblemisboundedandthatthesolutionsaremonotonedecreasing.Theupperbound,thevalueofthesolutionatzero,canbeapproximatedanalyticallyintermsofthephysicalparameters.Weobtainsolutionstotheboundaryvalueproblem,usingboththeTaylorseries(whichworkwellforweaknonlinearity)andthe(5-expansionmethod(validforstrongnonlinearity).Fromhere,weareabletodeducethequalitativebehaviorofthesolutionprofileswithachangeinanyoneofthephysicalparameters.

简介：Wakestructuresandvortexinducedvibration(VIV)ofaspring-supportedwide-D-sectioncylinderwereexperimentallyinvestigatedusinganX-wire,anovelphase-lockedparticleimagevelocimetry(PIV),andanaccelerationsensoratalowspeedwindtunnel.Comparedwiththefixedcase,the2P(twopair)vortexmodeasdefinedbyGovardhanandWilliamson(2000)ratherthanS(singlevortex)modeexistsinthewake.Thevelocitydeficitbehindthecylinderismuchlargerthanthatoffixedcase.Themeandragcoefficientincreasesfrom1.42forthefixedcaseto1.64forthevibratingcase.TheReynoldsstresspresentsevendistributionandsmallwithincreaseddistanceofX/D=-2toX/D=-10.Thepowerspectradensitybasedonacceleratorandhotwiredatapresentsahighlightidentical.Itshowsthatafterastronginteractionthecylindervibrationandthevortexsheddingcometoastablestate.Thevortexsheddingistotallylockedonandcontrolledbythecylindervibration.

简介：Thelargedesignfreedomofvariable-stiffness(VS)compositematerialpresupposesitspotentialforwideengineeringapplication.PreviousresearchindicatesthatthedesignofVScylindricalstructureshelpstoincreasethebucklingloadascomparedtoquasi-isotropic(QI)cylindricalstructures.Thispaperfocusesontheanti-bucklingperformanceofVScylindricalstructuresundercombinedloadsandtheefficientoptimizationdesignmethod.Twokindsofconditions,bendingmomentandinternalpressure,andbendingmomentandtorqueareconsidered.Influencesofthegeometricaldefects,ovality,onthecylinder'sperformancesarealsoinvestigated.Toincreasethecomputationalefficiency,anadaptiveKrigingmeta-modelisproposedtoapproximatethestructuralresponseofthecylinders.InthisimprovedKrigingmodel,amixedupdatingruleisusedinconstructingthemeta-model.Ageneticalgorithm(GA)isimplementedintheoptimizationdesign.TheoptimalresultsshowthatthebucklingloadofVScylindersinallcasesisgreatlyincreasedascomparedwithaQIcylinder.

简介：Ananalysisisperformedtostudytransientfreeconvectiveboundarylayerflowofacouplestressfluidoveraverticalcylinder,intheabsenceofbodycouples.Thesolutionofthetime-dependentnon-linearandcoupledgoverningequationsiscarriedoutwiththeaidofanunconditionallystableCrank–Nicolsontypeofnumericalscheme.Numericalresultsforthesteady-statevelocity,temperatureaswellasthetimehistoriesoftheskin-frictioncoefcientandNusseltnumberarepresentedgraphicallyanddiscussed.Itisseenthatforallflowvariablesasthecouplestresscontrolparameter,Co,isamplified,thetimerequiredforreachingthetemporalmaximumincreasesbutthesteady-statedecreases.

简介：3-DevolutionofKarmanvortexfilamentsandvortexfilamentsinbraidregionsintheturbulentwakeofa2-Dcirculaxcylinderisinvestigatednumeri-callybasedoninviscidvortexdynamicsbyanalyzingtheresponseoftheinitially2-Dspanwisevortexfilamentstoperiodicspanwisedisturbanceofvaryingmagnitude,wavelengthandinitialphaseangles.Ourresultsrevealakindof3-Dvortexsysteminthewakewhichconsistsoflargescalehorseshoe-shapedvorticesandsmallscaleλ-shapedvortexfilamentsaswellasvortexloops.Themechanismandthedynamicprocessaboutthegenerationofstreamwisevorticalstructureandthe3-Dcoherentstructurearereported.