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usedtorecordtheentireflamespreadproces. Propanolwassuedasfuel，sinceitprovidesacommondatabase
forustousetocompareourdatawithNASA'smicrogravitydata[Ros， 194;andMilerandRoss，192]andourpreviousexperiments[Ito， Masuda，andSaito，191;Ito，Saito，andCremers，195;andTashtoush， Narumi，Ito，Saito，andCremers，196]. Thefuelwasuniformlyig- nitedatoneendbyasmalpi10tf1ame. Highpresurenitrogenwas supliedfromanitrogencylindertoextinguishtheflame.
Therno・couples
Thetrajectoriesoftheseparticleswererecordedbyahighsped videocamerawhichwasconectedtoavideosystemandaTVmoni- torfortherealtimeobservationofbothf10wfieldandspreadingf1ame.
1nordertoconstructasingle2-Dflow-vectordiagrambycombin“ ingtheindependentlyobtainedgas-phasePTLSandliquid-phasePTLS， asmoke-tracetechnique(ST)wasapliedtovisualizetheoveralstruc- tureofflame-inducedairflowinthegasphaseandliquidconvectionin theliquidphasesimultaneously.Theglascontainerenclosingtheflame spreadtraywasfiledwithJapaneseincensesmoke.Thetraywasfiled withn-propanol;thefuelwassededwiththesmalaluminumpar- tic1esasusedfortheearlierPTLSmeasurements.Afterauniformsmoke layerwasfonnedovertheliquidsurface，thefuelwasignited.
DualWavelenαthHoloαraDhicInterferometrvlDWHn ThebasicprinciplesbehindDWH1arethesameasthoseforthe singleH1[Ito，Masuda，andSaito，191;Ito，Saito，andCremers，195; andTashtoush，Narumi，Ito，Saito，andCremers，196].Aschematic
ofDWHIisshowninFig.2.DWHIisanindirectmeasurementtech- niquewitharesponsetimeoflesthanamicrosecondandaspatial resolutionoflesthan土 0.1mminidentifyingconcentrationdifer- ence. TheDWH1hassignificantadvantagesoverthemicrosampling technique，whichhasaspatialresolutionofseveralmilimetersanda responsetimethatisatbestontheorderofasecond. 1nadition，the microsamplingtechniqueisadirecttechniquethatwilcausealarge physicaldisturbanceintheflowfield[Saito，Wiliams，andGordon，
1986].
Figure1 E}(perimentalapparatusofParticle-TrackLaser- Sheet(PTLS)system.
VelocitvMeasurementwithaParticleTrackLaserSheet Svstem(PTLSlandVisualizationofFlame-InducedAir FlowwithaSmokeTraceTechniaue(STTl
Fromourpreviousstudies[Qian，1shida，andSaito，194;and HiranoandSaito，195]，welearnedthataPTLStechniquewithahigh spedvideocamera(2ms/framewithashuterspedof0.2ms)serves bestofourpurpose. Withsignificantlyfewerparticles，thePTLScan measureprofilesofbothstreamlinesand2-Dvelocityprofilesnearly simultaneously. Ahighspedcamerasystemwithanultravioletlens andanimageintensifierwereusedtoobtainthevelocityofpartic1esin 500frames/ssped.Usinga4W Ar-ionlaserwithabeamstabilizer andacylindricalens，almmthickshetoflaserlightwithanaproxi- mately45degreopeninganglewasestablished(Fig.1)ai1dguidedby anopticalfibertotheplacewherethemeasurementnededtobedone.
Velocityprofilesoftheliquidandthegasconvectionweremea- suredindependentlyusingPTLS. Forthemeasurementofgasphase convection，ta1cparticlesweredisperseduniformlyoverthefuelsur- face.Forthemeasurementofliquidconvection，aluminumpartic1esof 15(土 5)μmdiameterweresprinkledontotheliquidsurface. Some aluminumpartic1esfloatedontheliquidsurfaceandothersenteredinto the liquid. The aluminum partic1es used were les s than 0.1 grams so thatthepartic1eshadlitleefectonthefuelproperties.
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Figure2 Aschematic01DWHIsystem.
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1nthepresentstudyweuseda2-DmodelofDWH1andexperi- mental1ydeterminedthebestposible2-Dconditionforthemeasure- men.tBecausethebasicprinciplesofDWH1aredetailedin[Spatzand Poulikakos，192;and1to，Narumi，Saito，andCremers，195]，wewil provideonlytheequationsforthetempera同 reandthefuelconcentra- tion，respectively.
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