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Turbulent Thermal Image Velocimetry at the Immediate Fire and Atmospheric Interface
  • +16
  • Marwan Katurji,
  • Jiawei Zhang,
  • Ashley Satinsky,
  • Hamish McNair,
  • Benjamin Schumacher,
  • Tara Marie Strand,
  • Andres Valencia,
  • Mark Finney,
  • Grant Pearce,
  • Jessica Kerr,
  • Daisuke Seto,
  • Hugh Wallace,
  • Peyman Zawar-Reza,
  • Christina Dunker,
  • Veronica Clifford,
  • Katharine Melnik,
  • Torben Grumstrup,
  • Jason Forthofer,
  • Craig B Clements
Marwan Katurji
University of Canterbury, New Zealand

Corresponding Author:[email protected]

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Jiawei Zhang
University of Canterbury
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Ashley Satinsky
University of Canterbury
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Hamish McNair
University of Canterbury
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Benjamin Schumacher
University of Canterbury
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Tara Marie Strand
Scion Research
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Andres Valencia
University of Canterbury
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Mark Finney
USFS
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Grant Pearce
Scion Rural Fire Research Group
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Jessica Kerr
Scion
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Daisuke Seto
University of Canterbury
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Hugh Wallace
New Zealand Forest Research Institute
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Peyman Zawar-Reza
University of Canterbury
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Christina Dunker
Rocket Lab
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Veronica Clifford
New Zealand Forest Research Institute
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Katharine Melnik
New Zealand Forest Research Institute
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Torben Grumstrup
Forest Service
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Jason Forthofer
Missoula Fire Sciences Lab
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Craig B Clements
Fire Weather Research Laboratory, Department of Meteorology and Climate Science
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Abstract

We present novel in-field vegetation fire observations, and the analyses used to process the data, using brightness temperatures recorded by longwave infrared camera and thermal image velocimetry. The brightness temperatures from a wind-driven stubble wheat fire were obtained in video format with a 60 frames per second (fps) acquisition rate. Multi-level sonic anemometers mounted on a 10m in-fire tower were used for in-situ measurements of turbulent velocity and air temperatures, while fuel level air and flame temperatures were collected by an array of thermocouples. The camera’s image pixel resolution was adequate to resolve dynamics and in accordance with the in-fire thermocouple spacing distances. The in-situ and remotely measured flaming zone dynamics were derived using two different methodologies, Thermal Image Velocimetry (TIV) and Image Segmentation (IS). The results highlight spatial and spectral information of coherent turbulent and mean velocity structures. The power spectra decomposition of the thermal image velocimetry showed similar spectral characteristics to the sonic velocity measurements during the fire passage under the tower with a similar inertial subrange slope. This result reveals plausible evidence of interaction between the flaming zone and wind turbulence for a prescribed rapidly moving stubble wheat fire. This research presents a new field measurement methodology for understanding fire-atmospheric interactions between the flaming zone and the immediate overlying atmospheric turbulent boundary layer.
27 Dec 2021Published in Journal of Geophysical Research: Atmospheres volume 126 issue 24. 10.1029/2021JD035393