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coversthetwinvortices. Ourotherpaper[13]wildiscusthefuelconcen仕ationprofilesformed inthegasphasejustaheadofthef1ame'sleadingedge. Theexistenceof也 issideイlows加 lC印 re wasfirstreportedbyMilerandRos[6]usinga20-mmwidetray. Wecon五rmedforalthe tbretray-widthcasesthat也epreheatedliquidextendedaheadofthef1amewi也 twinvortices f10wstructureσigures2，3aand4).
SpreadDirection FIGURE2TopviewofLSPTimageofliquidf10w1m mbelowsurface仕(aywidth:5mm).
Itwasfoundthatthelengthofthepreh剖 zoneaheadoftheflameisinverselyproportionalto 仕 a y w i d t h . B o t h b u o y a n c y a n d s u r f a c e - t e n s i o n f o r c e s l i k e l y g o v e m 白 is f1 0 w c i r c u l a t i o n . O n c e theflameleadingedgereachesthe企ontoftheliquidconvectionzone，itstopsordeceleratesto startanothercyc1e. Wealsoobservedthatthef1ameinclinationanglede:finedinreferences [10，1]issmalerintheacelerationstepthanindecelerationbecausethef1ameaceleration onlyocurswhenthegaseousfuel-airmixtureiswithi且 thef1amabilitylimit[13]. Figures3 showstwodiferent2-DP紅 tic1e-trackingimages(吟 beforejumpingand(b)afterjumping， whichwereobtainedbyLSPTfor吐le10m mwide仕 ay1m mbelowthefuelsurface. Figure4 showsfourdiferent2-DLSP紅 tic1e-仕ackingimages;(a)is1mmbelowthefuelsurface，(b)is2 mmbelowthe白elsurface，(c)is3mmbelowthefuelsurfaceand(の is5mmbelowthefuel surface.Figure5，aschematicofthe五g町 e4resultsandasideviewoftheliquidf10walongthe centerline，revealstheformationofcomplextw也 vorticesintheliquid.
町GURE3Twodiferenttopviewimagesofliquidf10wvisualizedbyLSPT，bo也 ほ 1mm belowthefuelsurface.(a)beforejumpingand(b)a武erJumping.
