Exploring three-dimensional coupled fire–atmosphere interactions downwind of wind-driven surface fires and their influence on backfires using the HIGRAD-FIRETEC model
J.-L. Dupuy A E , R. R. Linn B , V. Konovalov A C , F. Pimont A , J. A. Vega D and E. Jiménez DA Institut National de la Recherche Agronomique (INRA), UR 629 Ecologie des Forêts Méditerranéennes Site Agroparc, F-84914 Avignon cedex 9, France.
B Los Alamos National Laboratory (LANL), Earth and Environmental Sciences Division, Los Alamos, NM 87544, USA.
C Institute of Continuum Media Mechanics, Ural Branch of Russian Academy of Science, RU-614013 Perm, Russia.
D Centro de Investigacion Forestal – Lourizan, PO Box 127, E-36080 Pontevedra, Spain.
E Corresponding author. Email: dupuy@avignon.inra.fr
International Journal of Wildland Fire 20(6) 734-750 https://doi.org/10.1071/WF10035
Submitted: 27 March 2010 Accepted: 22 December 2010 Published: 1 September 2011
Abstract
The obstruction of ambient winds and the possible existence of indrafts downwind of a wildfire are aspects of coupled fire–atmosphere interaction influencing the effectiveness of a backfiring operation. The fire-influenced winds behind a headfire as well as their influences on backfire spread are explored using the three-dimensional HIGRAD-FIRETEC model. Fires are simulated under weak to strong wind speeds and in shrubland and grassland fuel types. The importance of three-dimensionality in the simulation of such phenomena is demonstrated. Results suggest that when fire–atmosphere interaction is constrained to two-dimensions, the limitations of air moving through the head fire could lead to overestimation of downwind indrafts and effectiveness of backfiring. Three-dimensional simulations in surface fuels suggest that backfires benefit from the obstruction of ambient winds and potentially the existence of an indraft flow in only a limited range of environmental conditions. Simulations show that flows are most favourable when the wildfire is driven downslope by a weak wind and the backfire is ignited at bottom of the slope. Model simulations are compared with backfiring experiments conducted in a dense shrubland. Although this exercise encountered significant difficulties linked to the ambient winds data and their incorporation into the simulation, predictions and observations are in reasonable agreement.
Additional keywords: backfire, indraft, suppression fire.
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