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

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

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