Flaming zone dynamics at the immediate fire and atmospheric turbulence interface
Dr Marwan Katjuri
University of Canterbury
Time & Place
Thu, 29 Oct 2020 16:00:00 NZDT in ER263
Novel experimental field observations and analysis methods of experimental fires reveal evidence of interaction between the flaming zone and the overlying wind turbulence for a rapidly moving stubble wheat fire. The in-situ and remotely measured (via high-speed longwave infrared camera) flaming zone dynamics highlight spatial and spectral information of coherent turbulent structures that are responsible for fire front fuel heating patterns (previously only observed in laboratory fire experiments). Thermal image velocimetry on spatially observed brightness temperature of the hot-air parcels and an in-fire sonic anemometer tower was used to measure atmospheric turbulence for pre-fire and fire passage periods. Results from turbulence spectral analysis using empirical mode decompositions show two main feedback mechanisms linking the fire and the atmosphere throughout integral lengths scales between 0.8 and 7.2 times the flame heights with important implications for future development of physics-based wildfire spread models and large eddy simulations of fire-induced atmospheric turbulence. While other studies focused on laboratory scale experiments and numerical simulations of fire spread and interactions with the larger atmospheric boundary layer scales, this research presents new results that help in understanding fire-atmospheric interactions at the intermediate scale between the flaming zone and the immediate overlying atmospheric turbulent boundary layer.