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Article Dans Une Revue Experimental Thermal and Fluid Science Année : 2012

Effects of slope on fire spread observed through video images and multiple-point thermal measurements

Xavier Silvani
Jean-Luc Dupuy

Résumé

A series of nine fire experiments was conducted on a large-scale bench with an inclinable plate to study the effects of a slope on fire spread. The temperature and total and radiant heat flux densities were measured at the top of the fuel bed during the upslope fire spread in still air. Measurements were recorded at 5 different locations ahead of the fire front. The effects of the slope on the flame topology, fire dynamics, and heat transfers ahead of the fire front were observed. The thermal measurements and image analyses showed a change in the fire spread regime and its related behavior with an increase in the slope. This was observed through an elongation of the flame and its contact surface over the upper part of the fuel bed. When the slope increased, the fire topology changed from a U-shape to a V-shape, and the radiation-dominated thermal environment ahead of the flame front was progressively turned into a mixed convective-radiative one, in which convection finally dominated for steep slope configurations. For fire spreading across a 30° slope, this increase in the curvature of the fire front (V-shape) is associated with the appearance of fire whirls rolling along the flanks of the fire front, which indicates significant changes in the fluid mechanics and heat transfers. The span of the heat transfer increased and a significant amount of energy impinged 1 or 2 m ahead of the flame front because of the flame tilt (radiation) and hot gas flow (convection). The measurements also indicated a greater amount of energy impinging in the center of the fuel bed than at the edge. This study shows the importance of investigating the fluid mechanics of fire in future wildfire researches.

Dates et versions

hal-00683163 , version 1 (28-03-2012)

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Xavier Silvani, Frédéric Morandini, Jean-Luc Dupuy. Effects of slope on fire spread observed through video images and multiple-point thermal measurements. Experimental Thermal and Fluid Science, 2012, 41, pp.1-15. ⟨10.1016/j.expthermflusci.2012.03.021⟩. ⟨hal-00683163⟩
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