iagodz/Supplementary-material-for-Impact-of-Urban-Morphology-on-Firebrand-Transport-and-Deposition: Complementary Files for Figure and Table Generation - Impact of Urban Morphology on Firebrand Transport and Deposition

Complementary files for figure and table generation for Impact of Urban Morphology on Firebrand Transport and Deposition.

Abstract: The transport and deposition of firebrand particles are key processes governing wildfire spread into urban environments. This study investigates how urban design, and the resulting turbulent boundary layer, influence the flight and landing patterns of firebrands. Large-eddy simulations were conducted to model turbulent flows over 12 idealized urban configurations, each represented by arrays of cubical structures with varying heights and spacings. In each case, tens of thousands of individual firebrands, modelled as mass- and size-changing spherical particles, were released and tracked to quantify the impact of topographic parameters on their motion and deposition. Across all urban cases, building-induced flow blockage, lower mean wind speeds, and elevated turbulence intensities led to shorter firebrand travel distances and flight times relative to a flat baseline case, while increasing crosswind dispersion. These effects were more pronounced in taller and denser urban layouts, where enhanced obstacle impingement and wake-induced low-velocity regions within the urban canopy increased surface deposition and altered deposition temperatures. Additionally, the firebrand smoldering rate was found to depend strongly on the topography layout, particularly due to the interaction of the firebrands with the building recirculation and local turbulence within the urban canopy layer. Denser configurations promoted faster burnout on wind-exposed rooftops, whereas taller, high-density layouts increased shielding within wake regions, allowing some firebrands to smolder for longer durations within the urban canopy layer. Overall, building height and compactness were found to have the largest impact on firebrand behavior, whereas building arrangement played a comparatively smaller role.