Comprehensive methodology for tracking burning firebrands in a vertical wind tunnel using multi-view video analysis

Background Burning debris (firebrands) can potentially travel significant distances to ignite spot fires many kilometres downwind of a wildfire, posing substantial challenges for fire spread prediction and management. Aim To improve our understanding of the combustion and flight behaviours of common bark firebrands through better quantification and detailed analysis of their motion, combustion and aerodynamic behaviour. Methods A custom firebrand tracking system consisting of three synchronised video cameras positioned orthogonally around the working section of a vertical wind tunnel was built and bespoke image processing algorithms developed to automatically reconstruct the 3D trajectory and combustion behaviour of a bark sample. Key results The system was found to accurately estimate bark sample position as well as spatial velocity, orientation changes and burnout profile. Conclusions A robust and accurate methodology to track the dynamic trajectory and behaviour of untethered burning bark falling at its terminal velocity was developed that overcomes many of the limitations of previous tracking approaches. Implications This study, applicable to a broad range of bark species as well as other firebrand materials under varying conditions, enables the development of more accurate predictive models of firebrand transport that will help improve the simulation and prediction of spotting in wildfires.