Physics-based modelling of junction fires: Effects of some topographical parameters in intersecting fires

Abstract

: A junction fire is the intersection of two fire fronts in a wildfire whose impact can be devastating. The rate of spread (ROS) of the junction point and the fire intensity can be intensified by slope and wind. The study of a junction fire using physics-based simulation tools aims to give an interpretation of the behaviour by examining the key factors that influence the fires, namely junction angle, slope and wind. In this research, at first, the physics-based model FIRESTAR3D was validated against a set of laboratory-scale junction fire experiments conducted with a shrub fuel bed. A grid resolution and domain size sensitivity study was carried out. Then numerical simulations of laboratory-scale junction fires were conducted using FIRESTAR3D under various junction angles (15° to 90°), on different slopes (0° to 40°) and with and without unidirectional wind conditions. Simulations were carried out under low and intermediate driving wind speeds (maximum 4 m/s). Fig. 1 represents the computational domain and an example of fire perimeter evolution showing the deceleration in the junction point advancement for non-slope cases.