Fire spread across pine needle fuel beds: characterization of temperature and velocity distributions within the fire plume
Thierry Marcelli A C , Paul A. Santoni A , Albert Simeoni A , Eric Leoni A and Bernard Porterie BA SPE, Université de Corse, UMR CNRS 6134, ERT FEUX, Campus Grossetti, B.P. 52, 20250 Corte, France.
B IUSTI–UMR CNRS 6595, ERT FEUX, Technopôle de Château-Gombert 5, Rue Enrico Fermi, 13453 Marseille Cedex 13, France.
C Corresponding author. Telephone: +33 4 95 45 01 61; email: marcelli@univ-corse.fr
International Journal of Wildland Fire 13(1) 37-48 https://doi.org/10.1071/WF02065
Submitted: 11 December 2002 Accepted: 27 May 2003 Published: 8 April 2004
Abstract
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.
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Appendix: Model equations
The general form of the transport equations of the gas phase is the following:
where 
is any transported property (species mass fraction, momentum through two velocity components, turbulent kinetic energy, rate of dissipation of turbulent kinetic energy, soot volume fraction or energy by means of the enthalpy); 
and 
are the diffusion exchange coefficient and source/sink terms for 
. They are summarized as follows:
The three source terms in the transport equation of soot account for the thermophoresis, formation, and oxidation processes, respectively, and ρs = 1800 kg/m3 is the soot density. The terms Fi, Sh, SYα, and 
are the drag force, the chemical sources of enthalpy and species as a consequence of thermal degradation of the fuel material, and the chemical source of species as a consequence of homogeneous reactions.
The shear and buoyancy turbulent production/destruction terms P and W can be expressed by
Equations of state
The gas is assumed to be a mixture of perfect gases and, including the chemical energy in the mixture static enthalpy, the equations of state will take the form
