The effect of fire front width on surface fire behaviour

Abstract

To determine the effect of fire front width on surface fire spread rates, a series of simultaneously ignited experimental fires was carried out in a pine plantation. Fires were ignited in plots with widths ranging from 0.5 m to 10 m and were burned in low wind conditions. Flame lengths were small in all fires, ranging from 20 cm to 60 cm. Since pre-heating of the forest litter from flame radiation is assumed to be an important mechanism in the spread of low intensity, low wind surface fires, it then follows that the width of a flaming front should effect on the heating of the fuel to ignition temperatures. Total flame radiation was also measured at a point 50 cm ahead of the advancing flame front for a number of the fires. Experimental results indicate that a flame radiation measured ahead of the fire stays fairly constant once the flame width is between 2 and 5 m. Theoretical flame radiation calculations confirm this trend. Rates of spread between the 5 and 10 metre width fires also appear to be similar; this indicates that, for the type of fires studied, once flame width is greater than about 2 m, radiation from any extra width of fire front has little effect on spread rate.

Nonlocal flow effects in bushfire spread rates

“…This would not change the normal or perpendicular component of the air flow into the fireline at all and so should not be expected to alter the spread rate of the fire; this is consistent with the experimental findings of Wotton et al (1999). On the other hand, because trailing flank fires draw air away from a head fire in a direction that is not parallel to the line of the head fire, they must act to reduce the air flow into the head fire; backing parts of the fireline would contribute in the same way.…”

“…The rate of advancement of the head fire is found to increase as the fire width increases, only approaching the limiting potential spread rate, which is the spread rate of a long linear fire front (Cheney and Sullivan, 1997), at relatively large fire widths. The experiments carried out by Wotton et al (1999) on fires between cleared channels, which eliminated any trailing flank fires and generated head fires that propagated as more-or-less linear fire fronts, do not appear to show such a reduction in spread rate. This suggests that it is a property of the fire itself, as well as the shape of the fireline, that leads to a reduction in spread rate.…”

Examining fuel treatment longevity through experimental and simulated surface fire behaviour: a maritime pine case study

“…The 25-year-old maritime pine stand was unpruned and is established in schist-based soil on a gentle slope facing southeast-southwest. Plots (10-15 m 2 ; 0.01-0.02 ha) -wide enough to reveal the fire behaviour potential associated with mild burning conditions (Wotton et al 1999) -were prepared for experimental fires within an approximate area of 2 ha. The plots were located either in untreated fuels, hereafter referred to as U25, or in 10-year-old fuels that had developed after low-intensity prescribed burning for hazard reduction, hereafter referred to as T10.…”

Towards Improved Airborne Fire Detection Systems Using Beetle Inspired Infrared Detection and Fire Searching Strategies

“…The flame width seems to be of minor influence on the radiation intensity near the flame front [29]. Here the determination of the flame height, LF, is the critical factor because characteristic values of the forest must be taken into account.…”