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house.A1thoughthetemperaturetemporari1ydecreasedby the 2nd water drop ping in the fire mature stage， it recoveredtothetemperaturebeforewaterdropingwithin severa1 minutes. The most noteworthy phenomenon ocured at the 5th water droping. The 5th water dropingconcentratedonhouseB4bythehoveringof the1argehe1icopter.A1thoughthefireseemedtohaveben extinguished in the video and the infrared images，it recovered to the temperature before water drop ping in about30min.Thereasonforthisisconsideredtobethat embers were stil smo1dering inside the scrap wood， a1thoughthefireonthesurfacewasout.
Fig.8(b)showsthepenetrationofthedropingwater intothecenterhouseB5.ThereasonforchosingB5was becausedropingwaterhititinthefireexpansionstage andthematurestage.Thecumu1atedamountofwateris shownonthehorizonta1axis，andhousetemperatureis shownonthevertica1axis.Symbo1plus(+)showsthat dropped water hit the house. The Ch-l and Ch-2 are thermocoup1es，whichmeasurethetemperatureinsidethe house at a height of 50 and 10 0cm from the grbund， respective1y.Inthefireexpansionstage，thetemperatureof Ch-l(50cm)decreasedgreat1ybythe白rstwaterdroping， whichindicatesthatwaterpenetratedthehouse.A1though dropingwaterhitthehouseinthefireexpansionstage， thetemperatureofCh-ldecreasedon1yslight1y.
3.3. Temperaturedrop，recoverytimeandrecovery temperature
Temperatures measured by thermocoup1es are not apropriateforjudgingtemperaturechangesofthewho1e house. So，infrared camera images were used for the temperatureana1ysis.
Fig.9showsatypica1temperaturechangeofaburning houseafterwaterdroping.Thehousetemperaturebefore waterdropingisdefinedbyTH andafterwaterdroping TL.Thetemperaturedropi1Tisexpresedbythefolowing equatlOn:
i1 T = T H - T L . (7)
ThetimetorecoverfromthetemperatureofTL to0.63i1T isdefinedasatimeconstantτ.Thetemperaturechangeof the house after water drop ping is expres sed by the folowingequationwhene1apsedtimeissetto:t
T(t)ニ 企 T(l-e-I/τ)+TL・ (8)
Although it recovers to the temperature before water dropinginthefireexpansionstage，thetemperaturedoes notrecovertothetemperaturebeforewaterdropingin either the fire mature stage or the dec1ine stage. The temperaturerecoveryfactorR isdefinedasthefolowing equationwhentherecoveringtemperatureissettoTR after waterdroping:
TH
TR TL+O.63~T
Q)
Thehousestobeusedfortheseana1ysesshou1dbethose thatdropingwaterhitmorethanothers，whichwerethe center house A3 in the first experiment and B4 in the secondexperiment.Theana1ysesarebasedonthosedata whendroppedwaterhitthehouses.Figs.10(a)-(c)，show the time constant τ，the temperature drop i1T and the temperaturerecoveryfactorRinre1ationtocoverage1eve1， respective1y.Thetimeconstantincreaseswiththecoverage 1eve1increaseasshowninFig.10(a).There1ationbetwen thetimeconstantandthecoverage1eve1isexpresedwith thefolowingequation:
τ=0.645D-0.39，
whereτdenotesthetimeconstant(min)andD denotesthe coverage 1eve1 (l/m2). The temperature drop becomes extreme1y1argewithinthecoverage1eve1of511m2 andit isconstantevenwithhighercoverage1eve1sasshownin Fig.10(b).There1ationbetwenthetemperaturedropand thecoverage1eve1isexpresedwiththefolowingequation:
i1T = 439 - 5.34 x 106e-6.17D. (11) Thetemperaturerecoveryfactordecreasesgreat1ywithin
t h e c o v e r a g e 1 e v e 1 o f 1 0 1 1 m 2 ， a n d it b e c o m e s c o n s t a n t beyond that. The re1ation betwen the temperature recovery factor and the coverage 1eve1 is shown in Fig.10(c)andisexpresedwiththefolowingequation:
R=40.0+82.26e-O.185D. (12) 3.4. Operationplaningforfiresupresionbyhelicopters
Making operation p1ans for fire sup pres sion invo1ves cho osing the size of he1icopters，he1ibucket vo1ume and fightconditionssuchasairsped，自ightheightandwater drop interva1s for firefighting. By cho osing he1ibucket
.
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.
吋 』一
目ー一ー ー『
ー-，- - - - -'- - - - ー- 色 lL 一「ー
Fig.9.Typicaltemperaturechangeofaburninghouseafterwater droping.Thehousetemperaturebeforewat巴rdropingisdefinedbyTH
andafterwaterdropingTL，thetemperaturedrop~T
fromTL to O.
temperatureisdefinedbyTR.
g Q)
←
ド
Time
thetimetorecover 63~T isd巴自nedasatimeconstant，r- therecovering
T.Konishietal./FireSafetyJournal43(208)363-375 371
，
R =TR - TL
-
i1T
(9)
、，ノ ハU 噌EEA /S E ¥
ny 0
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ρレ v
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