CEE Ph.D. Defense Announcement: Turbulent Fluid Dynamics of Wildland Fire-Atmosphere Interactions

Abstract: Complex turbulence patterns emerge from the interaction of a wildland fire-front with its surrounding atmosphere in a variety of terrain and ambient conditions. This interaction, referred to as fire-atmosphere interaction, frequently begets unexpected fire behavior that is difficult to control and threatens communities residing at the boundaries of wilderness. Fire–atmosphere interactions also inform ember-driven ignitions and smoke dispersion patterns that affect respiratory health and visibility downwind. Despite the progress made in recent decades and the operational utility of several fire models, a lot still needs to be understood about fundamental fire behavior to improve model predictive capabilities and expand their range of application.

This dissertation begins with the examination of wind velocity and temperature data collected during burn experiments ranging from small scales to operational scales (prescribed burns) for the turbulence processes characteristic of the presence of a fire in grassland and forested (canopy) environments. Given the spatial restraints on field measurements, we further attempt to investigate flow structures characteristic of buoyant-plume–canopy interaction under cross-wind forcing through large-eddy simulations (LES) using a low-complexity, "no-flame" setup. By varying ambient wind speeds and heat-source strength, we attempt to construct scaling laws informing plume deflection in canopy environments.

Comprehensive knowledge of these processes can help develop improved parameterizations for the process-level phenomena in coarser-resolution, fast-running, predictive fire-behavior and plume-dispersion models. Improved models can be utilized for the careful planning of prescribed burns intended to reduce hazardous fuels and forewarning fire managers regarding conditions conducive to unexpected fire behavior, leading to efficient wildland fire management practices.