ISS: Flame Spread Response to Non-steady Airflow

荒地附近的社区，特别是美国西部的社区，受到荒地火灾严重程度和频率增加的威胁。与此同时，这些火灾造成了更大地理区域的空气污染。该提案旨在通过提高预测火灾蔓延和增长的能力来降低这些火灾的严重性和影响。野火是非常动态的，风和燃料负荷迅速变化，但迄今为止，许多研究是基于稳定的分析。最近的研究提供了一个更完整的了解火灾的增长，特别是间歇性燃料加热的火焰的作用，但总体而言，有一个不稳定的（周期性或间歇性）火焰蔓延的基础研究的缺乏。这个项目的目的是研究蔓延的火焰对非定常强迫流动的响应，以更好地预测野火蔓延。这将通过混合对流（浮力和强制流）下的地面实验以及纯强制流下的微重力实验来实现。这些实验将描述和帮助解释非稳定流动条件下的瞬态火焰行为。这些知识将为研究界提供深入了解非稳态流动过程在野火蔓延中的作用。 这个项目将研究的物理机制，瞬态火焰行为的影响蔓延火焰与非稳定的并发气流使用实验和计算建模。该项目的目标是通过检查火焰间歇性燃料加热对火灾蔓延速度的作用，更好地预测野火蔓延。最近的研究发现，在某些火灾条件下，间歇性火焰加热过程可能是主要的传热过程，导致当前模型无法预测的火灾蔓延。因此，有必要发展一个野火蔓延的“可验证的物理理论”。本计画旨在借由研究非定常气流辅助下之火焰传播之相关基本问题，为发展此一理论之目标作出贡献。在这里，它建议使用非定常（周期性）的外部强制流实验模拟的间歇性流动引起的浮力不稳定性和/或湍流边界层。列入微重力实验将能够消除浮力效应，并更好地描述非稳定流的特征。这项研究将是第一个，如果不是第一个，专门调查火焰蔓延的非稳定，并发气流的反应实验研究之一。这个奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Communities near wildland areas, particularly those in the western United States, are threatened by increases in wildland fire severity and frequency. At the same time these fires contribute to air pollution over much larger geographical areas. This proposal seeks to reduce the severity and impact of these fires by improving the ability to predict their spread and growth. Wildland fires are very dynamic with rapidly changing winds and fuel loads yet much research to date is based on steady analysis. Recent research has provided a more complete understanding of fire growth, particularly the role of intermittent fuel heating from the flame, but overall, there is an absence of fundamental research on non-steady (periodic or intermittent) flame spread. The objective of this project is to study a spreading flame’s response to a non-steady forced flow to better predict wildfire spread. This will be accomplished through terrestrial experiments under mixed convection flow (buoyant and forced flow) as well as microgravity experiments with purely forced flow. These experiments will characterize and help explain transient flame behavior under non-steady flow conditions. This knowledge will provide the research community with insight into the role of non-steady flow processes in wildfire spread. This project will examine the physical mechanisms by which transient flame behavior impacts a spreading flame with a non-steady concurrent airflow using experiments and computational modelling. The goal of this project is to better predict wildfire spread by examining the role of intermittent fuel-heating from flames on the rate of fire spread. Recent research has found that intermittent flame heating processes can be the dominant heat transfer process under certain fire conditions, resulting in fire spread that is not predicted by current models. Thus, there is a need to develop a “verifiable physical theory” of wildfire spread. This project seeks to contribute towards the goal of developing such a theory by studying the related fundamental problem of flame spread aided by non-steady airflow. Here it is proposed to use a non-steady (periodic) external forced flow to experimentally simulate the intermittent flow induced by the buoyant instabilities and/or a turbulent boundary layer. Inclusion of microgravity experiments will enable removal of buoyancy effects and better characterization the non-steady flow. The proposed research will be one of the first, if not the first, experimental study specifically investigating the response of spreading flames to a non-steady, concurrent airflow.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.