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

The contribution of turbulent plume dynamics to long-range spotting

William Thurston A B C , Jeffrey D. Kepert A B , Kevin J. Tory A B and Robert J. B. Fawcett A

A Bureau of Meteorology, GPO Box 1289, Melbourne, Vic. 3001, Australia.

B Bushfire and Natural Hazards Cooperative Research Centre, Albert Street, East Melbourne, Vic. 3002, Australia.

C Corresponding author. Email: w.thurston@bom.gov.au

International Journal of Wildland Fire - https://doi.org/10.1071/WF16142
Submitted: 29 July 2016  Accepted: 17 February 2017   Published online: 22 March 2017

Abstract

Spotting can start fires up to tens of kilometres ahead of the primary fire front, causing rapid spread and placing immense pressure on suppression resources. Here, we investigate the dynamics of the buoyant plume generated by the fire and its ability to transport firebrands. We couple large-eddy simulations of bushfire plumes with a firebrand transport model to assess the effects of turbulent plume dynamics on firebrand trajectories. We show that plume dynamics have a marked effect on the maximum spotting distance and determine the amount of lateral and longitudinal spread in firebrand landing position. In-plume turbulence causes much of this spread and can increase the maximum spotting distance by a factor of more than 2 over that in a plume without turbulence in our experiments. The substantial impact of plume dynamics on the spotting process implies that fire spread models should include parametrisations of turbulent plume dynamics to improve their accuracy and physical realism.

Additional keywords: ember transport, fire spread, firebrands, Lagrangian particle transport model, large-eddy simulation, trajectories, turbulence.


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