The Medical Implications of Nuclear War (1986) / Chapter Skim
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2 A Review of the Physics of Large Urban Fires
2 A Review of the Physics of Large Urban Fires
Pages 73-95
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From page 73... ...
Atmospheric responses in the vicinity of a large smoke column are addressed, and the hazards expected to accompany nuclear fires are briefly discussed. HISTORY OF URBAN FIRES Disastrous urban fires have occurred throughout history.
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From page 74... ...
1838 Pittsburgh 1845 Philadelphia 1865 Portland, Maine 1866 Chicago 187150 8.6 Burned 1 day; 98,500 homeless; 17,500 homes lost Boston 1872 San Francisco 1906452 12.0 Earthquake-generated explosions and fires; 30 ignitions; burned 3 days; 100,000 homeless Halifax, Nova Scotia 19172,000 Tokyo 1923 1925 1932 Niigata, Japan 1925 Yamanaka, Japan 1931 Hakodate, Japan 19342,000 Generated fire storm Takaoka, Japan 1938 Boston 19421,000 Explosion and fire; burned 3 days; 3,000 injured; 300 missing Muramatsu, Japan 1946a Texas City 1947510 Fertilizer ship explosion Chungking, China 19491,000 Brussels 1967250 Burned 6 hours Chelsea (London, England) 1973 400 homes lost Anaheim, California 1982 500 apartments and 1 firehouse destroyed Philadelphia 1985 2 blocks of row houses gutted aApproximate date.
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From page 75... ...
In World War II, European cities suffered extensive fire damage. In several of the German cities attacked with incendiary weapons, fire storms developed (Bond, 19461.
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From page 76... ...
76 Cal o _ Cal ~ .
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From page 77... ...
Three to five minutes after the burst, dust and smoke from the already burning city could be seen following the rising nuclear fireball cloud. Figures 2 and 3 are previously unpublished views of Hiroshima taken in September 1945.
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From page 78... ...
78 PHYSICAL EFFECTS AND ENVIRONMENTAL CONSEQUENCES FIGURE 2 View of central Hiroshima in September 1945 showing rubble and reconstruction. (From the private collection of W
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From page 79... ...
At that point, the peak overpressure of the nuclear blast wave was about 3 psi, and the fireball heat or thermal fluence was about 8 or 9 cal/cm2. The surveyed area was composed mainly of industrial or commercial buildings, with some residential structures intermingled among them.
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From page 80... ...
From the limited past experience, it is clear that nuclear-caused urban fires can do extensive damage over very wide areas. Although such fires would be influenced by many factors, intense and widespread fires appear inevitable in the event of a nuclear attack on urban areas.
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From page 81... ...
Air temperatures in and near these huge fires may exceed the temperature of spontaneous ignition for most burnables. The rising column of hot air, smoke, ash, and combustion gases from a large urban fire can be expected to rise more rapidly, cool more slowly, and otherwise behave differently from that of a single house ~re.
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From page 82... ...
Multiple bursts on or near the same urban area can exacerbate the fire damage. A second burst can more readily light fires in the debris of a preceding burst.
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From page 83... ...
TABLE 5 Variables in Fire Damage Prediction Weapon yield Burst height Thermally induced fires Visibility/transmittance Ignition thresholds Fire propagation probabilities Clouds/snow cover reflectance Multiple bursts Blast-fire interactions Blast-induced fires Building construction Building contents/usage Building density Firespread Firebreaks Topography Weather Countermeasures/civil defense Preparation/evacuation Fire fighting Repair/recovery
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From page 84... ...
PHYSICAL EFFECTS AND ENVIRONMENTAL CONSEQUENCES 100 80 cr u. Lo 60 t_ LL ~ o 6 Z LL C' ~ UJ Z CL llJ The normalized power curve of Figure 6 can be approximated by the analytic formula (I + - )
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From page 85... ...
Although they represent a number of complex factors, recent studies (Brode and Small, 1984) have attempted to model TABLE 6 Approximate Threshold Radiant Exposure Needed for Ignition Threshold Radiant Exposure (cal/cm2)
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From page 86... ...
The range of possible fire sizes could be narrowed by choosing specific cities and weather conditions. Nevertheless, there are many variables that influence the prediction of fire size, and thus there may remain considerable uncertainty in damage or casualty prediction.
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From page 87... ...
Extreme temperatures and high-velocity fire winds were reported in each of these fires. We have developed analytical models that explain many of the phenomena observed in the World War II city fires and predict what might occur for a large-yield nuclear attack on an urban area.
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From page 88... ...
Pressure forces are created, and as a consequence, a broad upward motion supported by a highvelocity inward flow (the fire winds) is produced (Smith et al., 1975; Cox and Chitty, 1980; Zukoski et al., 19811.
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From page 89... ...
Those ratios represent the average of both the burning structure and street air temperatures. The street air temperatures are, of course, lower than the fire temperatures; nevertheless, the predicted mean values indicate an extremely hostile thermal environment for survivors of the blast.
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From page 90... ...
FIGURE 10 Fire wind dependence on burning rate: 10-km radius fire.
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From page 91... ...
Notable in the solutions are complex transient motions. Some local vortex motions account for periodically high centerline velocities that may loft combustion products through the tropopause; other vortices influence the ambient air induction (fire winds)
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From page 92... ...
so~ ask an . ~ = ~ m-= OGURE 13 Seam lines in atmosphchc chculabon generated by a 10-km radius 0~ 40 minutes after ignition.
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From page 93... ...
\ 10 6 / 0 5 P] ~ = ~ ma 10 15 20 as 30 HI ~ (a 35 40 45 so FIGURE 14 Seam lines in atmospbedc circulation chewed by a 10-km radius hm 1 bow ^r ignidon.
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From page 94... ...
Flame convection and radiative heating would produce a hostile temperature environment throughout an intensely burning city, even in the streets. Extreme thermal conditions and noxious gas accumulations would also be likely in shelters not properly designed to diffuse or dissipate the heat load and filter the smoky and poisonous air.
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From page 95... ...
The smoke load injected into the atmosphere by a nuclear war is the subject of a continuing study by us. A previously published study provided detailed estimates of smoke from attacks on nonurban targets (military strategic forces)
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