Author/Authors :
BoonchaiLertnuwat، نويسنده , , AsiBunyajitradulya، نويسنده ,
Abstract :
Comparativeeffectsbetweentheinterfacialshearconditionandthetrailing-cornerradius(ϕ)onthewakevortexofabubblearestudied.Intheinvestigation,thestandardk–ɛmodelisemployed,andthetwotypesofbubble:solidandgaseous,havedifferentinterfacialboundarycondition.Namely,forsolidbubblestheno-slipconditionisimposed,resultinginanon-zerointerfacialshearcondition,whileforgaseousbubblesthefree-slipconditionisimposed,yieldingazerointerfacialshearcondition.TheflowconditionissetforaslugflowwiththebubbledriftingataterminalvelocitycorrespondingtotheReynoldsnumberof35,000.Theresultsshowthat,theflowcanberoughlydividedintotwoflowregimes:thesmall-andlarge-ϕregimes.Inthesmall-ϕregime,thetrailing-cornerradiusplaysadominantroleandthedifferenceintheinterfacialshearconditionhaslittleeffectsonthewakevortex,causingthewakevorticesofthetwobubbletypestobesimilarinshape,size,andcirculation.Incontrast,inthelarge-ϕregime,theinterfacialshearconditioncanmanifestandaffectflowseparationandthewakevortex,causingsignificantdifferencesbetweenthewakevorticesfromthetwobubbletypes.Namely,asϕisincreasedtowardsthelarge-ϕregime,thewakevortexofthesolidbubblechangesrelativelylittlewhilethatofthegaseousbubblesignificantlydecreasesinsize.Atsmall-ϕthecirculationsaroundthewakevortexofbothtypesofbubblearealmostidenticalinitially.However,asϕisincreasedtowardsthelarge-ϕregime,thecirculationofthegaseousbubbledecreaseswithincreasingϕatamorepronouncedratethanthatofthesolidbubble.Theseresultsshowthatitistheabsenceofinterfacialshearinthelarge-ϕregimethatcausesthewakevortextobemoresensitivetothetrailing-cornerradius.
