UC Irvine

Embers are a potent mechanism for wildfire propagation because the particles can carry farther than the flame front and nullify defensible zones. PyroSim, a Fire Dynamics Simulator (FDS) tool that visually processes text editor inputs for simulating fire-driven fluid flow, is leveraged to model ember transport and accumulation patterns on buildings during a wildfire. This research begins with benchmark analysis against existing findings in literature for validating its usage. It focuses particularly on the transport and accumulation patterns of non-combusting particles with realistic ember parameters which are carried via wind over sample buildings. This study tested various ember sizes, ember densities, wind speed in the horizontal and vertical direction, rooftop styles, and fire effects to examine how each factor impacted ember behavior. Results indicate that roofs with a ridge line perpendicular to wind direction are more likely to accumulate embers. Additionally, horizontal and vertical wind speeds must be strong to facilitate ember transport but not so great that embers are unable to deposit and settle onto buildings. Regardless of building design, a plurality of embers come to rest against the front-facing walls of the structure, posing the biggest risk to fire spread. Surface fires impact flow behavior, so a ground fire was introduced to the model to examine how results change. Ultimately, it is theorized that fire-driven turbulence may facilitate ember transport but negate accumulation in unstable regions, such as rooftops.