ERI: Understanding the Role of Non-steady Wind Gusts in Wildfire Spread

极端火灾行为的增加（包括流行性和严重性）已经造成了大量的财产和人类生命损失，在大面积上产生了空气污染，并使大量人口流离失所。准确预测野火增长对于火灾响应（消防和疏散）以及预防措施（规定的燃烧和社区硬化）至关重要。该项目旨在通过更好地了解非稳定风对野火增长的作用，更好地抵御野火的负面影响。研究了火生长的两种物理机制：火焰驱动的火蔓延和火标形成。火焰驱动的火灾蔓延是火焰加热并点燃附近燃料的过程，而燃烧物发现是燃烧的碎片（燃烧物）被风和燃烧气体运送到它们可能点燃的燃料的过程。几乎所有这些过程的基础研究都集中在稳定条件下的火灾行为，而忽略了非稳定风（如阵风）的作用。对于燃烧植被产生的火把，风的作用是众所周知的，但它还没有得到充分的表征。本计画探讨是否可以用稳定流的结果来解释火蔓延与火标的产生行为，或者非稳定风是否会产生更极端的火行为。在该项目期间，与研究有关的野火主题教育模块将纳入一门研究生课程和一门本科课程。通过这些模块和学生参与研究，PI将帮助培养一个了解荒地和荒地-城市界面火灾的工程队伍，并培养对消防工程这些领域的兴趣。该项目将研究非稳态风与野火行为相互作用的物理机制，特别是火焰驱动的野火蔓延和火标发现，同时还使用成像方法对这些野火行为进行了新的测量。该项目的动机是促进改进野火蔓延的物理建模。目前的模型不能准确预测所有情况下的火灾蔓延。风通过对细燃料颗粒的间歇性对流加热强烈影响野火的蔓延，同时也有助于发现火焰。瞬态风的作用（即，阵风）在这些模型中没有被检验。该项目解决了社区确定的研究需求，即使用新的实验方法来表征火标生成和更全面的野火蔓延特征，以实现野火蔓延的可验证建模，以解决当前模型预测与观察行为之间的差距。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的知识价值和更广泛的影响审查标准。

Increased extreme fire behavior (both prevalence and severity) has caused substantial loss of property and human life, generated air pollution over large areas, and displaced large numbers of people. Accurate prediction of wildfire growth is vital for fire response (firefighting and evacuations) as well as preventative measures (prescribed burning and community hardening). This project seeks to better defend against these negative consequences of wildfires by better understanding the role of non-steady wind on their growth. Two physical mechanisms for fire growth are studied: flame-driven fire spread and firebrand spotting. Flame-driven fire spread is the process by which flames heat and ignite nearby fuel and firebrand spotting is the process by which burning debris (firebrands) are transported by the wind and fire gases to fuels which they may ignite. Nearly all prior fundamental studies of these processes have focused on fire behavior under steady conditions and have ignored the role of non-steady wind such as gusts. For firebrand generation from burning vegetation, the role of wind is known to be important, but it has not been fully characterized. This project examines whether fire spread and firebrand generation behavior can be explained with steady-flow results or if non-steady wind produces more extreme fire behavior. During the project, educational modules on wildfire topics related to the research will be incorporated into one graduate and one undergraduate course. Through these modules and student involvement in the research the PI will help prepare an engineering workforce knowledgeable about wildland and wildland-urban interface fire and cultivate interest in these areas of Fire Protection Engineering.This project will examine the physical mechanisms by which non-steady wind interacts with wildfire behavior, specifically flame-driven wildfire spread and firebrand spotting, while also making novel measurements of these wildfire behaviors using imaging methods. The motivation for the project is to facilitate improvement of physical modelling of wildfire spread. Current models do not accurately predict fire spread in all situations. Wind strongly influences wildfire spread through intermittent convective heating of fine fuel particles while also contributing to firebrand spotting. The role of transient wind (i.e., gusts) has not been examined in these models. The project addresses research needs identified by the community for firebrand spotting using new experimental methodologies to characterize firebrand generation and more comprehensive characterization of wildfire spread to enable verifiable modelling of wildfire spread to address the gap between prediction with current models and observed behavior.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.