Understanding the dynamics of inclined and wind-driven flames in wildland fires

Abstract

Time-dependent movements described as pulsing, puffing or swaying are among the most visible characteristics of open flames. Most existing models for wildfires, however, have assumed flames are motionless and spread at a constant rate via radiation, neglecting any clearly intermittent behaviour. Recent studies of spreading wildfires suggest that flame spread in fine fuel beds is driven by non-steady convective heating and intermittent flame contact on fuel particles. To further understand the impact and nature of these flame motions, a stationary, non-spreading fire configuration has been used as it allows for a thorough statistical analysis of the flame structure. The same intermittent heating observed in the fuel bed experiments were observed in the stationary burner, but with the ability to collect a larger data set. Scaling analyses which investigate the impact of these structures, theories on their generation and their impact to fire spread will be discussed for both wind-driven and slope-dominated flames.