Numerical investigation of the effect of wind, slope and fuel moisture on the radiative and convective heating of excelsior fuels

Background Wind, slope angle and moisture content are the three major parameters that affect fire rate of spread and heat transfer in propagating bushfires. Aims This study investigates the effect of the slope angle (0°–40°), wind speed (0–3 m s−1) and fuel moisture content (FMC, 4–12%) on convective heat transfer (cooling and heating) and radiative heat transfer of burning excelsior fuel particles at different locations downstream of a spreading fire. Methods The simulations were conducted using Fire Dynamics Simulator (FDS). The zone located downstream of the fire front was divided into two regions: the flame-induced region and the natural convection region. Key results For uplifted flames, there is convective cooling of particles downstream of the flame region. However, when the flame attaches to the unburnt fuel, flame depth and fire line intensity both increase, and there is convective heating of the particles ahead of the flames. Radiative heating of the particles also decreases consistently as the distance from the flame increases. Implications The results of this analysis reveal the mechanism of local convective and radiative heat transfer to downstream vegetation. Although heat transfer mechanisms are identified from this numerical analysis, these need to be verified through experimental work.