Heat Transfer Model for the Assemblage of Firebrands Over Surface Fuels

火标簇射（英语：Firebrand shower），又称余烬攻击，是指由于余烬在远离火线的植被或结构构件上产生、传输和积累而引发的点火。虽然现场火灾有助于野火的快速增长，并被认为是负责在荒地城市界面事件发生的重大损害，目前的理解的热量（能量）从火把的暴露表面的转移机制是不完整的。这个项目的主要目的是建立一个基本的知识，热（能量）从燃烧沉积物转移到受体表面。该项目的成果通过启用基于物理的现场火灾点火模块直接通知野火模拟器，从而更准确地预测和估计野火风险。该项目还将包括教育活动，如指导和培训本科生和研究生，与利益相关者和从业者的参与，以及在不同的工程/科学学科之间建立合作，以应对火灾科学的挑战。该项目的主要目标是使用系统的，可扩展的，准确的定量方法来量化从积累的火种到接收表面的热传递。具体而言，该项目执行以下任务：第一，进行数值模拟，使用四路耦合方法，以确定在惰性平面上的沉积模式的边界层内的火焰属性和它们的相互作用的影响。第二，将表面燃料形态纳入计算域，使用X射线计算机断层扫描（XCT），并定量识别其对燃烧剂沉积模式和传热的影响。第三，利用高保真模拟生成的数据，开发数据驱动的传热模型，并测试其准确性。所开发的模型使得研究结果适用于大规模（操作）野火模拟器，最终在一个基于物理的现场点火模块的开发。研究结果有望为现场火灾点火过程中的主要传热机制提供深入见解，并建立一个计算框架，用于量化从反应颗粒到周围墙壁的能量传递。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进行评估来支持。

Firebrand shower, also known as ember attack, is the ignition of spot fires due to the generation, transport, and accumulation of embers over vegetation or structural components away from the active fire lines. Although spot fires contribute to rapid wildfire growth and are known to be responsible for significant damages incurred at the Wildland Urban Interface incidents, the current understanding of the heat (energy) transfer mechanisms from firebrands to the exposed surfaces is incomplete. The primary aim of this project is to establish a fundamental knowledge of the heat (energy) transfer from firebrand depositions to the recipient surfaces. The outcomes of this project directly inform wildfire simulators by enabling a physics-based spot fire ignition module leading to more accurate forecasts and estimation of wildfire risk. The project will also encompass educational activities such as mentoring and training undergraduate and graduate students, engagement with stakeholders and practitioners, and creating collaborations between different engineering/scientific disciplines to address challenges in fire science.The main objective of this project is to quantify the heat transfer from the accumulated firebrands to the recipient surface using a systematic, scalable, and accurate quantitative approach. Specifically, the project performs the following tasks: First, conducting numerical simulations using a four-way coupled method to identify the effects of firebrand properties and their interactions within the boundary layer on the deposition patterns over an inert flat surface. Second, incorporating surface fuel morphology into the computational domain, using X-Ray Computed Tomography (XCT), and quantitatively discern its influence on firebrand deposition patterns and heat transfer. Third, leveraging the generated data from high-fidelity simulations, developing a data-driven heat transfer model, and testing its accuracy. The developed model makes the findings applicable for large-scale (operational) wildfire simulators, culminating in the development of a physics-based spot fire ignition module. The results are expected to provide insights into dominant heat transfer mechanisms involved in the spot fire ignition process and establish a computational framework for quantifying the energy transfer from reacting particles to the surrounding walls.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.