Interactions of non-intersecting oblique lines of fire burning in surface fuels in a combustion wind tunnel with and without wind

Abstract

Background High-intensity wildfires are often characterised by the interaction of multiple coalescing fires. Previously, results of investigation of obliquely intersecting lines of fire in a ‘V’ configuration in dry eucalypt forest litter were reported. Aim This article reports on investigation of the behaviour of separated non-intersecting lines of fire in the absence and presence of wind. Methods Experiments in the CSIRO Pyrotron combustion wind tunnel investigated interactions of lines of fire of 800 and 1500 mm lengths located at incident angles of 30° and 45° and separated at the closest point by 150 mm. Key results The behaviour of separated fires in wind was fundamentally different to that of fires burning in no wind and previous non-separated fires, sustaining separation for some time and distance before merging. Conclusions Although all fires showed evidence of interactions, the strength of interaction was greater in larger fires with more energetic flames, suggesting a key influence of the magnitude and rate of release and transfer of heat to unburnt fuels. Implications Future research should focus on quantifying contributions of aspects such as fuel combustibility and bulk density that contribute to and determine the convecto–radiative interactions of fires so such behaviour can be predicted a priori.