A semi-transparent model of bushfire flames to predict radiant heat flux
I.K. Knight A B and A.L. Sullivan AA CSIRO Forestry and Forest Products, PO Box E4008, Kingston, ACT 2604, Australia.
B Corresponding author. Telephone: +61 2 6281 8370; fax: +61 2 6281 8348; email: ian.knight@csiro.au
International Journal of Wildland Fire 13(2) 201-207 https://doi.org/10.1071/WF03047
Submitted: 21 May 2003 Accepted: 3 February 2004 Published: 29 June 2004
Abstract
The radiation emitted by a body is related through the Stefan-Boltzmann equation to the temperature of the emitting element. In the case of flame, the emitting elements are carbon particles. Existing models of bushfire flame radiation assume, however, that the flame radiates as a surface with an emissivity of 1 (i.e. a blackbody). This is only true when the flame is thick enough to provide a continuous wall of radiating carbon particles.
In this paper we propose a semi-physical model of radiant heat flux from bushfire flame that calculates the emissivity of the flame front based on its geometry and the optical properties of the flame. This model is calibrated using conservation of energy principles and empirical information about the radiant heat energy as a percentage of total energy of the flame. Comparisons are made with the flames generated by a propane-fuelled bushfire flame front simulator.
Additional keywords: modeling, flame radiation; firefighter safety.
Acknowledgements
We thank the NSW Rural Fire Service for funding the work to develop the bushfire flame front simulator and the semi-transparent flame model, Gameco Pty Ltd for building the simulator, and the members of the CSIRO Forestry and Forest Products Bushfire Behaviour and Management team for collecting the data from the simulator.
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