Paul Antoine Santoni

Fire spread across pine needle fuel beds: characterization of temperature and velocity distributions within the fire plume

The aim of this article is twofold. First, it concerns the improvement of knowledge on the fundamental physical mechanisms that control the propagation of forest fires. To proceed, an experimental apparatus was designed to study, in laboratory conditions, the flame of a fire spreading across a pine needle fuel bed. Characterization of temperature was managed by using a reconstruction method based on a double thermocouple probe technique developed recently. The vertical gas velocity distribution was derived from the previous reconstructed signals by measuring the transit time of a thermal fluctuation between two points of the flow. Second, the experimental data were used for the testing of a physical two-phase model of forest fire behavior in which the decomposition of solid fuel constituting a forest fuel bed as well as the multiple interactions with the gas phase are represented.

A two-dimensional model of fire spread across a fuel bed including wind combined with slope conditions

In a previous work (Santoni et al., Int. J. Wildland Fire, 2000, 9(4), 285–292), we proposed a twodimensional fire spread model including slope effects as another step towards our aim to elaborate a fire management tool. In the present study, we improve the model to include both wind conditions and wind combined with slope conditions. For this purpose the effect of wind and slope are considered similar, in the sense that they both force the flames to lean forward. However, this analogy remains acceptable only when flame tilt is below a threshold value. Simulation results are compared to experimental data under wind and no-slope conditions. The proposed model is able to describe the fire behaviour. Predictions of the model for wind and slope conditions are then considered and comparisons with observations are also provided.

Bulk and particle properties of pine needle fuel beds – influence on combustion

This paper presents a study to assess the influence of pine needle layer characteristics on combustion for three pine species of the Mediterranean region of France. It identifies the key parameters that explain the combustion of this fuel bed component. A relationship between permeability of the litter layer, fuel bed porosity and needle geometrical properties is presented. Although permeability was found to influence the rate of heat release from the combustion of litter independent of litter species, this was not the case for litter layers with similar mass and porosity. This study also stresses the important role of particle properties on their time to piloted ignition. The surface-to-volume ratio (SVR) of the species is the essential parameter driving the time to ignition as it defines the thermal thickness of single needles. This parameter also influences the combustion dynamics of litters under forced convection. In that case, the heat release rate of pine needle litters with the same permeability increases with the SVR of the species.

Discrete-event modelling of fire spreading

We deal here with the application of discrete-event System Specification (DEVS) formalism to implement a semi-physical fire spread model. Currently, models from physics finely representing forest fires are not efficient and still under development. If current softwares are devoted to the simulation of simple models of fire spread, nowadays there is no environment allowing us to model and simulate complex physical models of fire spread. Simulation models of such a type of models require being easily designed, modified and efficient in terms of execution time. DEVS formalism can be used to deal with these problems. This formalism enables the association of object-oriented hierarchical modelling with discrete-event techniques. Object-oriented hierarchical programming facilitates construction, maintenance and reusability of the simulation model. Discrete-events reduce the calculation domain to the active cells of the propagation domain (the heated ones).

Sampling and Quantitative Analysis of Smoke during a Fire Spreading Through a Mediterranean Scrub

This work consists in sampling and analyzing volatiles and smoke released by a typical Mediterranean vegetation during a fire. On an experimental burning plot, we used two original devices to collect volatiles and smoke. Thanks to air sampling pumps, atmosphere samples were taken, into cartridges filled with an adsorbent and into tedlar bags. The test site was instrumented with different other sensors (thermocouples, fluxmeters, anemometers, IR and visible cameras) in order to get the maximum data [1]. Analyses were performed at the laboratory by gas chromatography one day after the field experiment. Samples were thermally desorbed from the cartridges in the GC column coupled to a MS detector. We aim to characterize the risks related to the toxicity of smoke in actual conditions. Benzene, Toluene and Xylene (BTX) are highly toxic compounds that we propose to quantify in the smoke sampled during the fire. Quantification of such compounds was done with an external calibration using commercial mixtures of BTX.