简介：Basedonthevolumeoffluid(VOF)method,weconductanumericalsimulationtostudythehydrodynamicbinarycoalescenceofdropletsunderairflowinahydrophobicrectangularmicrochannel.Twodistinctregimes,coalescencefollowedbyslidingmotionandthatfollowedbydetachingmotion,areidentifiedanddiscussed.Additionally,thedetailedhydrodynamicinformationbehindthebinarycoalescenceisprovided,basedonwhichadynamicmechanicalanalysisisconductedtorevealthehydrodynamicmechanismsunderlyingthesetworegimes.Thesimulationresultsindicatethattheslidingmotionofdropletsisdrivenbythedragforceandrestrainedbytheadhesionforceinducedbytheinterfacialtensionalongthemainflowdirection.Thedetachment(i.e.,upwardmotion)ofthedropletisdrivenbytheliftforceassociatedwithanaerodynamicliftingpressuredifferenceimposedonthecoalescentdroplet,andalsorestrainedbytheadhesionforceperpendiculartothemainflowdirection.Especially,theliftforceismainlyinducedbyanaerodynamicliftingpressuredifferenceimposedonthecoalescentdroplet.TwotypicalregimescanbequantitativelyrecognizedbyaregimediagramdependingonReandWe.ThehigherReandWerespectivelyleadtorelativelylargerliftforcesandsmalleradhesionforcesactingonthedroplet,bothofwhicharehelpfultodetachmentofthecoalesceddroplet.

简介：Indouble-pulselaser-inducedbreakdownspectroscopy(DP-LIBS),thecollinearfemtoseconddouble-pulselaserconfigurationisexperimentallyinvestigatedwithdifferentinitialsampletemperaturesusingaTi:sapphirelaser.Theglasssampleisablatedtoproducetheplasmaspectroscopy.Duringtheexperiment,thedetectedspectrallinesincludetwoNa(I)lines(589.0nmand589.6nm)andoneCa(I)lineatthewavelengthof585.7nm.Theemissionlinesaremeasuredatroomtemperature(22°C)andthreehigherinitialsampletemperatures(Ts=100°C,200°C,and250°C).Theinter-pulsedelaytimerangesfrom-250psto250ps.Theinter-pulsedelaytimeandthesampletemperaturestronglyinfluencethespectralintensity,andthespectralintensitycanbesignificantlyenhancedbyincreasingthesampletemperatureandselectingtheoptimizedinter-pulsetime.Forthesameinter-pulsetimeof0ps(single-pulseLIBS),theenhancementratioisapproximately2.5atTs=200°CcomparedwiththatobtainedatTs=22°C.Forthesameinter-pulsetimeof150ps,theenhancementratiocanbeupto4atTs=200°CcomparedwiththatobtainedatTs=22°C.Thecombinedenhancementeffectsofthedifferentinitialsampletemperaturesandthedouble-pulseconfigurationinfemtosecondLIBSaremuchstrongerthanthatofthedifferentinitialsampletemperaturesorthedouble-pulseconfigurationonly.