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During the past 20 years, study of wind-slope-aided wildland fire behaviour with experimental burns and physical modelling methods has increased. As part of their continuing study of fires in Mediterranean shrub, F. Morandini and X. Silvani reported experimental temperatures, heat fluxes, flame characteristics and other fire behaviour variables measured on five wind-slope-aided fires. Calculating convection numbers and several convective Froude numbers, the authors concluded that these dimensionless variables for their two wind-dominated fires did not satisfy criteria identified in previous studies for determining mechanisms of heat transfer during fuel preheating. The present paper describes a re-analysis of the data based on a triangular flame model and alternative definitions of flame tilt angle and height. This new analysis has shown that the influence of slope on the fire behaviour was not accounted for; thus, the conclusion of Morandini and Silvani is questionable. Of the five dimensionless variables studied using criteria in the literature, the squared flame height convective Froude number best describes modes of heat transfer to unburned fuels during the experimental fires. Though these results come indirectly from field measurements, they confirm the need to include slope effects in descriptions of wind-slope-aided fire behaviour. F. Morandini and X. Silvani reported experimental heat fluxes and fire behaviour variables for five fires in Mediterranean shrub. They concluded that the calculated dimensionless variables for their two wind-driven fires did not satisfy previously reported criteria for identifying modes of heat transfer during fuel preheating. Re-analysis of the data has shown that the influence of slope on the fire behaviour was not accounted for and that the squared convective Froude number best describes mechanisms of heat transfer during the fires. [ABSTRACT FROM AUTHOR]

The article discusses studies related to wildfires including "Experimental development of a fire management model for jarrah," by N. D. Burrows and "Forest fire behavior. In Forest Fire: Control and Use," by G. M. Byram.

The article cites a study on the flame characteristics of 22 wind-aided pine litter fires in a laboratory wind tunnel and 32 field fires in southern rough and litter grass fuels. The study used the flame model of Albini as a starting point for developing flame height and tilt angle models for wind-aided fires. The study was aimed to describe with mathematical models and experimental data how air entrainment and combustion regimes determine flame characteristics.

The application of a next-generation dead-fuel moisture model, the 'Nelson model', to four timelag fuel classes using an extensive 21-month dataset of dead-fuel moisture observations is described. Developed by Ralph Nelson in the 1990s, the Nelson model is a dead-fuel moisture model designed to take advantage of frequent automated weather observations. Originally developed for 10-h fuels, the model is adaptable to other fuel size classes through modification of the model's fuel stick parameters. The algorithms for dead-fuel moisture in the National Fire Danger Rating System (NFDRS), on the other hand, were originally developed in the 1970s, utilise once-a-day weather information, and were designed to estimate dead-fuel moisture for mid-afternoon conditions. Including all field observations over the 21-month period, the Nelson model showed improvement over NFDRS for each size fuel size class, with r² values ranging from 0.51 (1000-h fuels) to 0.79 (10-h fuels). However, for observed fuel moisture at or below 30%, the NFDRS performed better than the Nelson model for 1-h fuels and was about the same accuracy as the Nelson for 10-h fuels. The Nelson model is targeted for inclusion in the next-generation NFDRS. [ABSTRACT FROM AUTHOR]

G. M. Byram (1959) proposed a method for computing the ratio of the vertical flux of buoyancy generated by a wildfire (power of the fire P f ) to the horizontal flux of kinetic energy due to the atmospheric winds (power of the wind P w). Utilizing this power ratio in his case studies of wildfires, Byram concluded that when the ratio exceeds unity for at least 0.3 km above the fire, phenomena associated with blowup behavior such as firewhirls, spotting, and strong indrafts occur. Though Byram made this claim over 40 years ago, there has been little effort on the part of fire researchers to test it. Byram's calculation of P f describes an ideal case—a fire that burns in a neutrally stable atmosphere and does not entrain atmospheric air into its convection column. In the present paper, these restrictions are relaxed and Byram's calculations are repeated for a fire whose column entrains air from a non-neutral atmosphere. The new model yields a P f that is smaller than Byram's P f by a factor of about 2, is weakly dependent on stability, and is independent of entrainment above a height of 0.5 km. Both models are moderately restricted in that column processes involving liquid water are not considered. [ABSTRACT FROM AUTHOR]

The article discusses a study entitled "Flame characteristics for fires in southern fuels," by R.M. Nelson.