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ThePETbotlerocketwhichimitatedthefire-fightingwaterbucketwasatachedintheuper part(2030mmheight)ofascafoldtower.WaterwasputintotheinsideofaPETbotle，theair presurewaschargedbythecompresor，andwaterwasspurtedfromthedischargehole.The spedofthespurtedwaterwhichblowsoutfromatankwascontroledbychangingtheair presure(O.lMPatoO.6MPa)inatankandthequantityofwater(100mlto50ml).Thetarget f10wvelocitywassetforsatisfiedwithequation(12)，sothatFroudenumber.Furthermore，the sidewindwassprayedonthefalingwaterfromthewindtunel，andthesituationwherethe helicopterwasf1yingwasreproduced. Sidewindvelocitywaschanged(5m/sto 16m/s)for diferentf1yingcondition.Thespreadbehaviorofair-dropedwaterwastakenvideobythehigh spedcamera，andanalyzedthevelocityvectorusingf1uidimageanalysissoftware(Flow-vec32).
Experimentforcrashedwαterimpact
Forthesetingoftheconditionforsatisfiedwithequation(13)，themodelbecomessimilarityas theinertiaforceandsurfacetensionofthewater.Itmeanstheexperimentforimpactofwater whenthewaterhittheground.The1:4scalingsmalpresuretankwhichimitatedthebucket wasproducedasshowninFig.3.Thepresuretankwhichimitatedthefire-fightingwaterbucket wasatachedintheuperpart(2400mmheight)ofascafoldtower.Waterwasputintothe insideofatank，theairpresurewaschargedbythecompresor，andwaterwasspurtedfromthe dischargehole.Thespedofthespurtedwaterwhichblowsoutfromatankwascontroledby changingtheairpresure(O.lMPatoO.6MPa)inatankandthequantityofwater(1literto5 li社ers).Thetargetf10wvelocitywassetforsatisfiedwithequation(13)，sothatWebernumber. Theimpactloadwhenthedropedwaterclashedwiththegroundwasmeasuredbytheloadcell. Thereceiverpartoftheloadcelis330mmlengthand330mmwidth.Themeasurementinterval oftheloadcelwassetto10msec.
Fr・氾 l le Tank
Loa1ccel Compressor
(a)Presuretank (b)Schematicofexperimentalaparatus Fig.3.Experimentalaparatusforcrashedwaterimpact.
