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A Methodology for Experimental Quantification of Firebrand Generation from WUI Fuels


Over the past few years, numerous large-scale disasters have occurred due to wildfires at the wildland-urban interface (WUI). In these fires, spread via the transport of firebrands (burning embers) plays a significant role. Several models have been developed to describe the transport of firebrands but few, if any, are available which can provide a quantitative means to generate firebrands at the source of a fire. In this regard, a new methodology is proposed here that uses a wind tunnel to experimentally quantify the generation of firebrands from WUI fuels under different ambient conditions. The setup allows for the collection of all generated solid firebrands and major downstream gaseous species concentrations. Unique firebrand yield correlations can then be generated for each tested fuel, while also accounting for the heat-release rate, providing unique validation targets for numerical simulations. Generation of firebrands from branches of two conifers at a fixed wind speed of 4 m/s are presented to demonstrate the capabilities of this new methodology. A carbon mass balance was utilized to analyze preliminary results and understand how much of the fuel mass transitions to firebrands vs. gases. These results provide a description of the mass burning process and ultimately tie firebrand production to a time-dependent heat-release rate for initialization of firebrand transport in numerical simulations. An average firebrand yield ranging from 3–4% of initial dry mass is ultimately presented for lodgepole pine and Douglas fir. Future work is required with larger fuel sizes pertaining to real wildfire scenarios; however, the presented methodology can provide valuable data needed to initialize numerical simulations of firebrand transport, necessary for reconstruction of WUI fires and to aid in the development of mitigation strategies for the prevention of future disasters.

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This work was supported by the National Institute of Standards and Technology (NIST) under award number # 60NANB18D243. The authors would like to thank Ben Biallas, Xingyu Ren, and Sriram Bharath Hariharan for their help in experimentation as well as instrumentation and Chelsea Phillips and Sara McAllister from the USDA Forest Service for acquiring fuels. MG would also like to thank Kevin McGrattan, who suggested the current line of work, as well as Kathryn Butler, Kuldeep Prasad, Randy McDermott, Isaac Leventon, Samuel Manzello, Jiann Yang, and Nelson Bryner for their support and advice throughout the course of this project.

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Correspondence to Michael J. Gollner.

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Hajilou, M., Hu, S., Roche, T. et al. A Methodology for Experimental Quantification of Firebrand Generation from WUI Fuels. Fire Technol 57, 2367–2385 (2021).

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  • Firebrand Generation
  • Wildland Urban Interface (WUI)
  • Wildland Fire
  • Vegetative Fuels