Craig Clements San José State University Shaorn Zhong Michigan State University Xindi Bian and Warren Heilman Northern Research Station, USDA Scott Goodrick Southern Research Station,USDA Turbulence Kinetic Energy and Fire- Turbulence Kinetic Energy and Fire- Induced Winds Induced Winds Observed during Observed during FireFlux FireFlux Seventh Symposium on Fire and Forest Meteorology 23-25 October 2007 Bar Harbor, Maine
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Craig Clements San Jos é State University Shaorn Zhong Michigan State University
Turbulence Kinetic Energy and Fire-Induced Winds Observed during FireFlux. Craig Clements San Jos é State University Shaorn Zhong Michigan State University Xindi Bian and Warren Heilman Northern Research Station, USDA Scott Goodrick Southern Research Station,USDA. - PowerPoint PPT Presentation
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Craig ClementsSan José State University
Shaorn ZhongMichigan State University
Xindi Bian and Warren HeilmanNorthern Research Station, USDA
Scott GoodrickSouthern Research Station,USDA
Turbulence Kinetic Energy and Fire-Induced Turbulence Kinetic Energy and Fire-Induced WindsWinds Observed during FireFluxObserved during FireFlux
Seventh Symposium on Fire and Forest Meteorology23-25 October 2007Bar Harbor, Maine
• Fire-induced surface winds were 2-3 times stronger than ambient winds.
• A convergence region formed downwind of the fire front, but was shorter in duration than expected.
• Inflow velocities were much weaker than expected.
• Observed instantaneous upward vertical velocities were on the order of 10 m s-1 and downward vertical velocities = 5 m s-1
• Directly measured sensible heat fluxes were ~28.5 kW m-2 occurred at higher levels in the plume rather than near the surface.
• However, estimated instantaneous heat fluxes at the surface were on the order of 0.8 - 1.0 MW m-2.
Summary and Conclusions
•The observed TKE during the grass fires increased due to the variance in the ambient wind component (fire direction) rather than the contribution from all three velocity components.
•The turbulence within the upper fire plume, is isotropic and equally driven by both buoyancy and wind shear.
• While near surface turbulence is anisotropic and driven by variance in the horizontal momentum rather than buoyancy.
•This suggests that although buoyancy is important, mechanically generated wind shear is responsible for the observed turbulence in grass fires.