Transport of Particles in a Canopy Flow with a Buoyant Plume and Gaps

Spot fires occur when smoldering firebrands, or embers, are lofted by a main wildfire, carried downwind, and ignite new fires upon landing. Forest canopies where wildfires occur often include gaps, such as fuel breaks or wildland urban interfaces, which may affect the flow. Here, we present the results of experiments designed to understand the effects of canopy gaps on the transport of particles. We imaged particles in a flume with an array of wooden dowels, a heated plume, and various gap lengths. We find that particles travel farther the shorter the gap is when no plume is present. The presence of a plume substantially increases dispersion, partially washing out the signal of the gaps. Results have ramifications for modeling firebrand transport and for designing mitigation measures.