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: 1603947
• 负责人: Shankar Mahalingam
• 金额: $ 18万
• 依托单位: University of Alabama in Huntsville
• 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 2021-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1603947&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更多近距离的火焰如何融合成单一的火焰。这一信息的直接应用是活灌木中的荒地火灾，比如加利福尼亚州的Chaparral。与死亡的植物不同，活的植物的特点是能够保持大量的水分。一些树叶最初被点燃，来自单独树叶的火焰合并成一个大火焰。以类似的方式，来自个别灌木的火焰融合在一起，往往形成更强烈的火焰，能够更快地传播。例如，单个树叶的火焰高度只有2至5厘米，但由于火焰融合，灌木的火焰可能达到10至12米的高度。将在3-D几何形状的树叶、木桩或冰棒棒上进行小规模实验，以检验间距如何影响火焰融合行为。描述火焰合并的关联性将基于间距、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。这些模拟将进一步直接调查灌木丛和相邻灌木丛之间的合并火焰行为。从实验和模拟相结合的活动中得出的火焰合并行为的广义关联式可能适用于建筑物、工厂、燃料堆和其他可燃材料的火灾。这项研究的结果将被用于为STEM教育工作者和学生开发教育材料。对水平方向上的射流或池火的火焰合并进行了研究，并建立了火焰合并行为的关联式。然而，三维火焰融合对于活灌木的点火以及建筑火灾都很重要。小规模的实验将在固体燃料元件上进行，如树叶、木钉或冰棒棒，作为垂直和水平分离距离的函数。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，并建立火焰行为的关联。将对小规模实验进行基于物理的建模，以帮助确定火焰融合的最重要机制。然后，模拟将扩展到描述相邻灌木在有风和没有风的情况下的火焰合并。经验关联的可扩展性将通过与多个灌木模拟进行比较来确定。预计这种火焰合并行为的相关性将为耗时的大型景观火灾的计算流体力学模拟提供一种合理的替代方案。

项目成果

A computational study on the fire merging of burning chamise shrubs

燃烧灌木丛火融合的计算研究

• 发表时间: 2019
• 期刊: 11th U.S. National Combustion Meeting
• 作者: Habib, M.A.;Anand, C.;Mahalingam, S.;Shotorban, B.
• 通讯作者: Shotorban, B.