Journal of the International Association of Wildland Fire
RESEARCH ARTICLE

# Numerical prediction of size, mass, temperature and trajectory of cylindrical wind-driven firebrands

Luis A. Oliveira A C , António G. Lopes A , Bantwal R. Baliga B , Miguel Almeida A and Domingos X. Viegas A
+ Author Affiliations
- Author Affiliations

A ADAI/LAETA, Department of Mechanical Engineering (FCTUC – Polo II), University of Coimbra, PT-3030-201 Coimbra, Portugal.

B Department of Mechanical Engineering, McGill University, 817 Sherbrooke Street, West Montreal, QC, H3A 0C3, Canada.

International Journal of Wildland Fire 23(5) 698-708 https://doi.org/10.1071/WF13080
Submitted: 21 March 2012  Accepted: 20 March 2014   Published: 27 June 2014

## Abstract

Mathematical models and numerical solution procedures for predicting the trajectory, oscillation, possible rotation, and mass and size time-evolution of cylindrical wind-driven firebrands are described and discussed. Two test problems and the results, used for validating the mathematical models, are presented. In one, experimental measurements of non-burning cylindrical particles falling in still air are compared to numerical predictions and in the other, predictions of time-evolution of mass and size of stationary burning particles in air flows are compared with experimental results reported in the literature. Results yielded by the proposed models for a demonstration problem involving cylindrical wind-driven firebrands, with the same initial volume, mass and position, but different initial aspect ratios and distinct initial orientations relative to the wind velocity, are then presented. These results show the following: the horizontal distance travelled by the firebrand from release to landing locations is an increasing function of its initial aspect ratio; and the initial orientation of the firebrand, and its subsequent oscillations including possible rotation, have a significant influence on its trajectory, thus it is important to account for them in mathematical models formulated for predicting the spread of fires by spotting.

Additional keywords: horizontal distance travelled, mathematical models, oscillations, rotations, spot fires, total falling time, trajectories.

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