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Experimental study on the evolution of canyon fire spread behavior under different terrains and the critical conditions for eruptive fire

Jiale Fan, Boxuan Chen , Yan Guo, Chenze Bu, Jiangxue Gao, Xu Dou, Haiqing Hu, Long Sun, Tongxin Hu

Abstract

[Background] The spread of canyon fire often involves sudden acceleration, which is related to eruptive fire. [Aims] The purpose is to explore the pattern of fire line evolution and rate of spread (ROS) with topographic conditions in canyon fire, and to clarify the critical conditions and mechanism of eruptive fire. [Methods] A systematic experimental study on canyon fire was conducted by initiating dead pine needles with a point ignition. [Key results] Four different types of fire line contours are identified under different topographic conditions. When α (central slope angle) ≥ 15°, the direction of fire heads gradually deviates from the line of maximum slope and moves to the centerline, and this deviation increases with α. Accordingly, ROS along the centerline also exhibits dynamic characteristics, and ROS increases with α and δ (lateral slope angle). The critical conditions of eruptive fire are α = 27.5° and δ= 20°. [Conclusions] When eruptive fire occurs, there is significant convective heating ahead of the fire front. This strong convective heating is the basic mechanism of eruptive fire in canyons. [Implications] Our results can provide a theoretical basis for commanders to make decisions.

WF24134  Accepted 15 September 2025

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