Vortex Dynamics of a Smoldering Firebrand Particle

In wildfires, spotting is a complex process that is known as the major mechanism of propagation of fires to unburned areas and nearby communities. In this mechanism, burning debris (known as firebrand or flying ember) is transported by the turbulent wind and ignites local fuel upon landing. Firebrand flight behavior, their landing distribution, and thus, spot fire risks are critically dependent on the interaction of the evolving firebrands with the immediate wind field and the physical characteristics of the particles. Despite numerous research on firebrand transport, investigation of the effect of temperature on the aerodynamic forces acting on firebrand particles is lacking in the literature. In this study, we develop a Direct Numerical Simulation (DNS)-based computational model to investigate the effect of spatiotemporally evolving temperature of a spherical firebrand particle on its aerodynamic forces. The temperature evolution of the firebrand particle is obtained from a novel surface-energy balance model, which is capable of handling objects with complex-shape geometries and multiple material properties.