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

Observations of energy transport and rate of spreads from low-intensity fires in longleaf pine habitat – RxCADRE 2012

B. Butler A D , C. Teske B , D. Jimenez A , J. O’Brien C , P. Sopko A , C. Wold A , M. Vosburgh A , B. Hornsby C and E. Loudermilk C
+ Author Affiliations
- Author Affiliations

A USDA Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory, Missoula, MT 59801, USA.

B Center for Landscape Fire Analysis, University of Montana, Missoula, MT 59812, USA.

C USDA Forest Service, Southern Research Station, Athens Fire Laboratory, Athens, GA 30602, USA.

D Corresponding author. Email: bwbutler@fs.fed.us

International Journal of Wildland Fire 25(1) 76-89 https://doi.org/10.1071/WF14154
Submitted: 4 September 2014  Accepted: 16 July 2015   Published: 15 December 2015

Abstract

Wildland fire rate of spread (ROS) and intensity are determined by the mode and magnitude of energy transport from the flames to the unburned fuels. Measurements of radiant and convective heating and cooling from experimental fires are reported here. Sensors were located nominally 0.5 m above ground level. Flame heights varied from 0.3 to 1.8 m and flaming zone depth varied from 0.3 to 3.0 m. Fire ROS derived from observations of fire transit time between sensors was 0.10 to 0.48 m s–1. ROS derived from ocular estimates reached 0.51 m s–1 for heading fire and 0.25 m s–1 for backing fire. Measurements of peak radiant and total energy incident on the sensors during flame presence reached 18.8 and 36.7 kW m–2 respectively. Peak air temperatures reached 1159°C. Calculated fire radiative energy varied from 7 to 162 kJ m–2 and fire total energy varied from 3 to 261 kJ m–2. Measurements of flame emissive power peaked at 95 kW m–2. Average horizontal air flow in the direction of flame spread immediately before, during, and shortly after the flame arrival reached 8.8 m s–1, with reverse drafts of 1.5 m s–1; vertical velocities varied from 9.9 m s–1 upward flow to 4.5 m s–1 downward flow. The observations from these fires contribute to the overall understanding of energy transport in wildland fires.

Additional keywords: energy transport, field measurements, fire behaviour, fire modelling.


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