Fire Safety Science Digital Archive

Effects of wind velocity and slope on fire spread rate and flame length were examined. Fuel beds of vertical sticks (13.97 cm x 0.455 cm x 0.1 10 cm) and coarse excelsior were burned in an open-topped tilting wind tunnel. Mean fuel moisture content of sticks and excelsior was 11% and 12%, respectively. Mean surface area to volume ratio was 23 cm-! Five slopes (negative, positive, none) were combined with five wind velocities (heading, backing, none). Spread rate was measured with thermocouples; flame length was estimated from video imagery. Mean spread rate ranged from 0.001 to 0.06 m/s. Spread rate of downslope heading fires exceeded spread rate of no-wind/no-slope fires. Mean flame length ranged from 0.08 to 1.69 m; 0.25 m was the maximum observed for most backing fires. Increased fuel moisture reduced spread rate and flame length. Data indicate that the current formulation of an empirical wildland fire spread model is inappropriate.