Study of wildfire in-draft flows for counter fire operations

Abstract

The use of counter-fires to gain control over wildfires is a technique used by some fire services around the world. A fire is purposely lighten ahead of the wildfire and the buoyancy induced in-drafts pull it towards the flame front thus creating a fire break of burnt fuel. Well used, this technique is fast, effective and safe. However, no technical research has been done on the subject. Without understanding of the mechanisms, counter-firing remains a difficult technique and can lead to unnecessary risks being taken or opportunities lost. This paper uses computational fluid dynamics to study the in-draft created around wildfires. A generalized structure of the in-draft velocity profile composed of three zones is observed. The length of the different zones are analysed to find the dependence with fire intensity and wind velocity.