Experimental Research on Upslope Fire and Jump Fire

This paper presents an elementary analysis on the difference and similarity between upslope fire and jump fire, by a series of experiments performed in laboratory. The rate of spread (ROS), fire line angle (separation angle of the two fire lines), angular velocity of fire line, flame residence time and nondimensional radiant heat transfer for the two kinds of phenomena are investigated. For upslope fire, it is found that ROS remains almost steady for line ignition, while it increases with time for point ignition. For upslope fires with line ignition, the fire line angle decreases with time from the initial 180 o to a steady small value, while for point ignition, the initially generated fire line angle remains steady. The angular velocity of fire line does not depend on slope angle in an upslope fire with line ignition. For jump fire, the ROS first increases sharply and then decreases gradually, and it depends on slope angle more significantly than the initial fire line angle. The fire line angle increases with time, and the angular velocity of fire line varies with slope angle. For upslope fires with line ignition, the flame residence time increases with slope angle, while it remains almost constant for upslope tests with point ignition. For jump fire, under one specific initial fire line angle, the overall mean residence time increases with increasing slope angle. Nondimensional heat radiation for fuel preheating is calculated which effectively explains the ROS development in upslope fire with line ignition and jump fire.