Analysis of the large urban fire environment: part 2: Parametric analysis and model city simulations.

Final report; September 1981-September 1982

This report considers the fire environment that would result from a megaton-yield nuclear weapon explosion. An analysis that treats the physics of the burning zone and the volume immediately above it (turning region) is used to predict the velocity, temperature, and pressure fields of large area fires. A sensitivity study explores the influence of turbulence, radiation, fire size, and burning intensity on the mean temperature levels and velocity fields. The results show hurricane-force velocities developing as the fire size or burning rate is increased. A sample calculation illustrates the change in firewind velocities as the fire evolves over time. Calculations of the burning region for three model urban areas show the influence of building density and urban sprawl on the resulting fire environment. An additional set of predictions accounts for reduction of the fire intensity by blast in the urban center. For the latter cases, the temperature distribution is changed markedly, though the magnitude of the induced fire winds is not appreciably reduced .550.