4.5 Turbulent kinetic energy and fire-induced winds observed during FireFlux

Wednesday, 24 October 2007: 9:30 AM
The Turrets (Atlantic Oakes Resort)
Craig B. Clements, San Jose State Univ., San Jose, CA; and S. Zhong, W. E. Heilman, X. Bian, and S. L. Goodrick

Observations from the FireFlux experiment are used to determine the production and magnitude of the turbulent kinetic energy and structure of the fire-induced flow fields during fire front passage. Results from the instrument towers placed within the fuel bed show that surface level winds reverse 180 degrees very briefly during the convergence in-flow period that forms downwind of the fire front. The magnitude of the inflow winds was also very weak. Once the fire front passed, the wind speed tripled in magnitude greater than pre-fire conditions. Observed turbulence kinetic energy was five times greater during the fire front passage than before the fire. Analysis of the turbulence showed that the turbulence was anisotropic due to the variance in the ambient wind rather than by buoyancy production. These new observations provide a basis to further our understanding of the dynamics of wildland grass fires and their interactions with the atmosphere. This paper will also discuss the limitations of measurement systems used to measure turbulence in the fire environment.
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