Experimental and Modeling Study of Risk from Ember Storms

野火环境中的现场火灾是由余烬进入大气并远远吹到野火主要锋面之前而引起的。本研究的目的是建立一个经过实验验证的野火余烬飞散的随机模型。该研究计划将建立在现有的关于余烬飞行的确定性模型的基础上，并开发分析和数值模型，以解释问题的内在随机性质。这些模式将包括对余烬大小和形状、火灾大小和强度以及火焰羽流和大气边界层中的湍流速度波动的概率分布函数的参数化。模型将通过在大型边界层风洞中进行的一系列积灰飞行实验进行验证。这些实验将测量各种尺寸、形状和风力条件下的放样高度和顺风运输距离。这将为放样余烬的飞行距离提供实验测量。经过实验验证的数值模型将用于进行参数敏感性研究，以确定对余烬发现和起火的顺风风险影响最大的参数。现场火灾可能造成重大财产损失，并可能危及房主和消防员的生命安全。了解余烬是如何升入大气，然后顺风吹来的机理，将极大地增强我们预测现场火灾风险的能力，并改进我们对此类威胁的反应。该项目将通过解决涉及的过程的随机性质来改变余烬飞行的建模方式。最终目标是减轻野火环境下现场火灾造成的财产损失。研究小组将制定一项公共推广计划，教育在校学生有关野火的风险，并鼓励学生在科学和工程领域从事职业。外展计划将以南卡罗来纳州的学校为重点，通过演示考试以及将在网上提供的视频和其他材料。

Spot fires in wildfire environment are caused by embers lofted into the atmosphere and blown well ahead of the main front of the wildfire. The objective of this research is to establish an experimentally verified stochastic model for ember flight in wildfires. The research program will build on existing deterministic models for ember flight and develop analytical and numerical models that account for the inherently stochastic nature of the problem. The models will include parameterizations of the probability distribution functions for ember size and shape, fire size and intensity, and the turbulent velocity fluctuations in fire plume and the atmospheric boundary layer. The models will be verified through a series of ember flight experiments conducted in a large scale boundary layer wind tunnel. The experiments will measure lofting height and downwind transport distance for a broad range of sizes, shapes, and wind conditions. This will provide experimental measurements of the flight distance for lofted embers. The experimentally verified numerical model will be used to perform parametric sensitivity studies to establish those parameters that most greatly influence the downwind risk of ember spotting and starting fire. The spot fires can cause significant property damage and can endanger the lives of home owners and firefighters. Understanding the mechanics of how embers are lofted up into the atmosphere and then blown downwind will greatly enhance our ability to predict the risk of spot fires and improve our response to such threats. The project will transform the way that ember flight is modeled by addressing the random nature of the processes involved. The ultimate goal is to mitigate property losses caused by spot fires in wildfire environment. The research team will develop a public outreach program to educate school students about the risks from wildfires, and to encourage students to pursue careers in science and engineering. The outreach program will be focused on South Carolina schools through demonstrations of the tests and videos and other materials that will be made available on the web.