FIREBRAND ACCUMLATION ZONES IN FRONT OF STRUCTURES IN WILDLAND-URBAN INTERFACE (WUI) FIRES

摘要

It is well known that as structures are exposed to wind, stagnation planes are produced. Past work byrnthe authors demonstrated for the first-time that wind-driven firebrand showers may accumulate in thesernstagnation planes. While those experiments demonstrated this important phenomenon, due to thernlimited duration of firebrand showers of the original NIST batch feed Firebrand Generator, it was notrnpossible to perform a more systematic study. To this end, a series of detailed experiments werernperformed using the recently developed NIST Continuous-Feed Firebrand Generator capable ofrnfirebrand showers of unlimited duration. Full-scale walls of varying orientation were placedrndownstream of the device and the wind speed was varied in increments up to 10 m/s. The experimentsrnwere conducted in the Building Research Institute’s Fire Research Wind Tunnel Facility (FRWTF).rnFor a given wall orientation exposed to specific firebrand size/mass distribution, it was observed thatrnwind speed influences not only the spatial location and extent of the accumulated firebrands in thernstagnation plane in front of the wall, but also the nature of the smoldering combustion intensity of thernaccumulated firebrands. The data may be used to provide guidance to appropriate separation distancesrnthat combustibles should be placed near structures and is also of great use to validate CFD models ofrnfirebrand transport.