The interaction of wind and fire

Abstract

The rate of spread of a wildfire increases markedly when a wind springs up. Why and how this happens is still not completely understood. However, by using a judicious mixture of laboratory experiments, field experiments, sensitivity analyses of existing wildfire spread models and physical reasoning it is possible to identify some features that have not been adequately considered in the past. In particular: (i) the energetics of wind-blown wildfires indicate that a fire-wind may not exist and that the wind may blow through the fire line. ii) The rate of spread of the fire-front depends on the atmospheric stability such that the fire-front speeds are 50% or more faster during winds in the 2 to 6 m/s range under unstable conditions. iii) The wind speed acting on the flame provides an upper limit to the flame propagation speed. Existing attempts to constrain the propagation rate of fire-spread models at high wind speeds appear incorrect and, iv) wind fluctuations interacting with the standing fuel generate sweeps of downward air which carry the flame into the fuel bed and directly preheat the fuel. a

Role of buoyant flame dynamics in wildfire spread

“…Explaining Flame Structure Saw-toothed flame geometry (20) was observed repeatedly in laboratory-scale and field-scale fires, both stationary and spreading. This flame geometry was followed by stream-wise streaks of smoke and flames behind the flame zone (Fig.…”

“…If convection is modeled at all, turbulent diffusion is assumed (18). It is known, although, that flames in spreading fires can exhibit periodic behavior (19) and intermittently sweep or burst forward to heat and ignite fuel particles (20)(21)(22)(23), but these reports provide little insight into the origins or structure of these flame bursts or consequences for particle ignition. Here we report previously…”

Environmental Constraints on Living Organisms

“…All these factors may vary in space and time, adding variability to the intrinsic variability of fire as a turbulent phenomenon [3]. Variations in fire severity have been noticed for a long time in Lamto, with records of exceptionally intense fires (1967) occurring under especially favorable conditions (long dry periods, high fuel load, high wind speed).…”

“…Fire behavior is influenced by many factors [61], among which the most important are fuel load [36], fuel quality [27], wind [3], slope [58], air humidity and air temperature [5]. All these factors may vary in space and time, adding variability to the intrinsic variability of fire as a turbulent phenomenon [3].…”

Linking Landscape Fires and Local Meteorology ─ A Short Review

“…(13), (14), (17), (20) and (21). The review by Beer (19) provides a good overview of the interaction of wind and fire and the paper by Raupach (18) is a useful summary of the non-dimensional scaling of a fire plume subjected to ambient winds. Some of the research has found its way into monographs, such as Refs.…”