International Journal of Wildland Fire International Journal of Wildland Fire Society
Journal of the International Association of Wildland Fire
RESEARCH ARTICLE

An improved non-equilibrium model for the ignition of living fuel

A. Lamorlette A C , M. El Houssami B and D. Morvan A
+ Author Affiliations
- Author Affiliations

A Aix Marseille Univ, CNRS, Centrale Marseille, M2P2, Marseille, France.

B BRE Centre for Fire Safety Engineering, The University of Edinburgh, UK.

C Corresponding author. Email: aymeric.lamorlette@univ-amu.fr

International Journal of Wildland Fire 27(1) 29-41 https://doi.org/10.1071/WF17020
Submitted: 6 February 2017  Accepted: 21 October 2017   Published: 23 January 2018

Abstract

This paper deals with the modelling of living fuel ignition, suggesting that an accurate description using a multiphase formulation requires consideration of a thermal disequilibrium within the vegetation particle, between the solid (wood) and the liquid (sap). A simple model at particle scale is studied to evaluate the flux distribution between phases in order to split the net flux on the particles into the two sub-phases. An analytical solution for the split function is obtained from this model and is implemented in ForestFireFOAM, a computational fluid dynamics (CFD) solver dedicated to vegetation fire simulations, based on FireFOAM. Using this multiphase formulation, simulations are run and compared with existing data on living fuel flammability. The following aspects were considered: fuel surface temperature, ignition, flaming combustion time, mean and peak heat release rate (HRR). Acceptable results were obtained, suggesting that the thermal equilibrium might not be an acceptable assumption to properly model ignition of living fuel.


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