CAREER: Understanding the Mechanisms of Wildland Fire Spread

职业：了解荒地火灾蔓延的机制

• 批准号: 1554026
• 负责人: Michael Gollner
• 金额: $ 50万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-01 至 2020-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1554026&HistoricalAwards=false
• 关键词: CAREER; Understanding; Mechanisms; Wildland; Fire

CBET-1554026, GollnerLarge wildland fires pose an enormous threat to local populations and natural resources, and contribute carbon and particulate emissions to the atmosphere. Firefighters, community planners, and local residents all depend on accurate predictions of the spread of wildland fires for operational firefighting, evacuations, community design, and prescribed fire design. It is well known in the wildland fire community that increasing winds or slope will increase the rate of spread of a wildfire; however, the physical mechanisms by which a fire spreads are not well known. This uncertainty is, in part, why no models can accurately predict the critical thresholds for fire spread. Important thresholds include when a fire will extinguish or transition from surface fire spread to crowning through the tree-tops. This research project will utilize laboratory experiments to develop quantitative models to describe the physics of fire spread. Once these improved models for fire spread are developed, they can be used for predicting fire suppression, evacuations, and fire weather alerts. Solving the wildfire problem will take more than just advanced research. A workforce trained to understand both the practical and scientific fire problems in wildland fire will also be necessary. In conjunction with this project, two outreach programs will be implemented. First, an educational program for middle and high school girls will use fire science as a unique avenue to introduce underrepresented students to STEM careers. Second, researchers will work with the first responders - wildland firefighters, to inform them of hazards and safety techniques. The research objective of this proposal is to understand the previously-unexplored role of intermittent heating that is driven by reacting-flow instabilities on wildland fire spread, in the hope that this knowledge may lead to a testable, physical theory of wildland fire spread. Current models either rely on empirical results or assume that radiation is the dominant heat transport mechanism. Recent observations by the PI and his collaborators have instead shown that intermittent heating from flames is, in many regimes, an equally important process driving flame spread and cannot be neglected. Buoyant instabilities originating in the reacting flow of wildland fires eject flames far ahead into unignited fuel, driving the spread. During the most devastating wildfires, these regimes tend to be dominant and, hence, current flame spread models fail. This study of intermittent fuel heating will contribute to these important numerical tools which will address critical failures during extreme fire conditions. Experimental work will include the use of stationary burners under forced-flow, inclined, and combined configurations. In addition, a pulsed-gas burner will be used to couple the effects of flame instabilities on fine fuel ignition which drive flame spread. Theoretical work will include developing theoretical models and scaling relationships for the formation of coherent structures in the flow and their effects on intermittent heating of fine fuels. The development of new models and collaboration with the U.S. Forest Service will propel these results directly into practice and couple the disparate fields of wildland fire and combustion science.

大型野火对当地人口和自然资源构成巨大威胁，并向大气排放碳和颗粒。消防员、社区规划者和当地居民都依赖于对野火蔓延的准确预测来进行消防、疏散、社区设计和规定的火灾设计。众所周知，在野火界，增加风或坡度会增加野火的蔓延速度；然而，火灾蔓延的物理机制尚不清楚。这种不确定性部分地解释了为什么没有模型能够准确地预测火灾蔓延的临界阈值。重要的阈值包括火灾何时会熄灭或从地表火势蔓延到树冠的过渡。本研究计划将利用实验室实验发展定量模型来描述火灾蔓延的物理过程。一旦这些改进的火灾蔓延模型被开发出来，它们就可以用于预测灭火、疏散和火灾天气警报。解决野火问题需要的不仅仅是先进的研究。此外，还需要一支训练有素、了解野外火灾的实际和科学问题的工作队伍。与此项目相结合，将实施两项外展计划。首先，一项针对初高中女生的教育计划将利用火灾科学作为一种独特的途径，向代表性不足的学生介绍STEM职业。其次，研究人员将与第一响应者——荒野消防员合作，告知他们危险和安全技术。本提案的研究目的是了解由反应流不稳定性驱动的间歇性加热对野火蔓延的先前未被探索的作用，希望这一知识可能导致野火蔓延的可测试的物理理论。目前的模型要么依赖于经验结果，要么假设辐射是主要的热传输机制。PI和他的合作者最近的观察表明，在许多政权中，火焰的间歇性加热是推动火焰传播的一个同样重要的过程，不能忽视。在野火的反应流中产生的浮力不稳定性将火焰喷射到前方未点燃的燃料中，从而推动了火势的蔓延。在最具破坏性的野火中，这些制度往往占主导地位，因此，目前的火焰蔓延模型失败了。这项间歇燃料加热的研究将有助于这些重要的数值工具，这些工具将解决极端火灾条件下的关键故障。实验工作将包括在强制流动、倾斜和组合配置下使用固定燃烧器。此外，还将采用脉冲气体燃烧器来耦合火焰不稳定性对驱动火焰蔓延的精细燃料点火的影响。理论工作将包括发展理论模型和在流动中形成连贯结构的比例关系及其对精细燃料间歇加热的影响。新模型的开发以及与美国林务局的合作将推动这些成果直接付诸实践，并将荒地火灾和燃烧科学的不同领域结合起来。

项目成果

Boundary layer instabilities in mixed convection and diffusion flames with an unheated starting length

• DOI: 10.1016/j.ijheatmasstransfer.2017.11.040
• 发表时间: 2018-03
• 期刊: International Journal of Heat and Mass Transfer
• 影响因子: 5.2
• 作者: Colin H. Miller;Wei Tang;Evan Sluder;M. Finney;S. McAllister;J. Forthofer;M. Gollner

Flame spread and burning rates through vertical arrays of wooden dowels

• DOI: 10.1016/j.proci.2018.09.008
• 发表时间: 2019-01-01
• 期刊: PROCEEDINGS OF THE COMBUSTION INSTITUTE
• 影响因子: 3.4
• 作者: Jiang, Lin;Zhao, Zhao;Gollner, Michael J.
• 通讯作者: Gollner, Michael J.

Thermal structure of the blue whirl

• DOI: 10.1016/j.proci.2018.05.115
• 发表时间: 2019
• 期刊: Proceedings of the Combustion Institute
• 影响因子: 3.4
• 作者: S. Hariharan;Evan Sluder;M. Gollner;E. Oran