Collaborative Research: Merging of Horizontally and Vertically Separated Flames in Wildland Fires

合作研究：野火中水平和垂直分离火焰的融合

• 批准号: 1603316
• 负责人: Thomas Fletcher
• 金额: $ 18万
• 依托单位: Brigham Young University
• 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: 2016-08-15 至 2020-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1603316&HistoricalAwards=false
• 关键词: Collaborative; Research; Merging; Horizontally; Vertically

1603316 - Fletcher1603947 - MahalingamThis project will study how two or more flames in close proximity merge into a single flame. The immediate application for this information is wildland fires in live shrubs, like in the California chaparral. Living vegetation is characterized by its ability to hold large quantity of moisture, unlike dead vegetation. A few leaves are initially ignited, and the flames from the separate leaves merge into one large flame. In a similar manner, flames from individual shrubs merge to often form a more intense fire, capable of spreading faster. For example, flame heights from individual leaves are only 2 to 5 cm, but flames from shrubs may reach heights of 10 to 12 m due to flame merging. Small-scale experiments will be performed on leaves, wood dowels, or popsicle sticks in 3-D geometries to examine how spacing affects flames-merging behavior. Correlations that describe flame-merging will be based on spacing, heat release, and other variables, and then compared with physics-based fluid dynamics simulations. The simulations will further enable direct investigation of merged flame behavior in shrubs and between adjacent shrubs. Generalized correlations of flame-merging behavior derived from the combined experimental and modeling activities can possibly be applied to fires in buildings, factories, fuel piles, and other combustible materials. Findings from this research will be used to develop educational materials for STEM educators and students. Flame merging has been studied for jets or pool fires spaced in a horizontal plane, and correlations for flame merging behavior have been developed. However, three-dimensional flame-merging is important for ignition of live shrubs, as well as building fires. Small-scale experiments will be performed on solid fuel elements such as leaves, wood dowels, or popsicle sticks as a function of vertical and horizontal separation distance. Experiments will be performed with and without wind. Flame behavior will be monitored with video and IR cameras, and correlations of flame behavior will be developed. Physics-based modeling of the small-scale experiments will be performed to help identify the most important mechanisms for flame merging. The simulations will then be extended to describe flame merging of adjacent shrubs, with and without wind. The scalability of the empirical correlations will be determined by comparison with the multiple shrub simulations. It is expected that such correlations of flame merging behavior will provide a reasonable alternative to time-consuming computational fluid dynamics simulation of large landscape fires.

1603316 -Fletcher 1603947-Mahalingam这个项目将研究两个或多个火焰是如何在接近合并成一个单一的火焰。这些信息的直接应用是在活灌木丛中的荒地火灾，就像在加州的查帕拉尔。活的植被的特点是它能够保持大量的水分，不像死的植被。最初点燃几片叶子，然后分开的叶子的火焰合并成一个大的火焰。以类似的方式，从个别灌木火焰合并，往往形成一个更激烈的火灾，能够传播得更快。例如，来自单个叶子的火焰高度仅为2至5厘米，但来自灌木的火焰由于火焰合并而可达到10至12米的高度。小规模的实验将进行树叶，木榫，或冰棒在3-D几何形状，以研究间距如何影响火焰合并行为。描述火焰合并的相关性将基于间距、热释放和其他变量，然后与基于物理的流体动力学模拟进行比较。模拟将进一步使合并火焰行为在灌木和相邻灌木之间的直接调查。从实验和模拟活动相结合的火焰融合行为的广义关联，可能适用于火灾的建筑物，工厂，燃料堆，和其他可燃材料。这项研究的结果将用于为STEM教育工作者和学生开发教育材料。 本文研究了水平面内射流或池火的火焰融合，并建立了火焰融合行为的关联式。然而，三维火焰融合是重要的点燃活灌木，以及建筑火灾。将对树叶、木钉或冰棒棍等固体燃料元件进行小规模实验，作为垂直和水平间隔距离的函数。实验将在有风和无风的情况下进行。将用视频和红外摄像机监测火焰行为，并建立火焰行为的相关性。将进行基于物理的小规模实验建模，以帮助确定火焰合并的最重要的机制。然后，模拟将扩展到描述火焰合并相邻的灌木，有风和无风。经验相关性的可扩展性将通过与多灌木模拟的比较来确定。预计这种火焰融合行为的相关性将提供一个合理的替代费时的计算流体动力学模拟大型景观火灾。