CAREER: Understanding the Role of Buoyancy Flow for Accurate and Robust Scale Modeling of Upward Flame Spread

职业：了解浮力流在向上火焰蔓延的精确且稳健的比例建模中的作用

• 批准号: 1942282
• 负责人: Ya-Ting Liao
• 金额: $ 50万
• 依托单位: Case Western Reserve University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1942282&HistoricalAwards=false
• 关键词: CAREER; Understanding; Role; Buoyancy; Flow; CAREER; Understanding; Role; Buoyancy; Flow

This project will study how fire behaviors change with scale. Laboratory-scale tests are often used in fundamental research and in technical standards to characterize the burning behaviors of materials. However, key fire behaviors change when moving from small laboratory scale to larger real-world scales found in structures or forest fires. This scalability problem is a long-standing challenge in fire science, one that limits generalizability of laboratory testing. Filling this knowledge gap will improve the relevance of standard safety tests and lead to safer structures and products. Ultimately this will save lives, money, and property for society. This project employs experiments, numerical simulations, and theoretical modeling to control, study, and predict fire behavior at various scales. The focus will be on a phenomenon called buoyancy flow, which varies significantly with scale. The developed scaling models will be validated against real-world testing databases maintained by industry collaborators. This project will also help cultivate the next generation of academic and industry leaders. This will be achieved via interactive public demonstrations of fire dynamics and via promotion of technical standards in college curricula. One of the key factors influencing fire scalability is buoyancy flow. This project will focus on the effects of buoyancy flow on upward flame spread over solids. In this fire scenario, the fuel sample is oriented vertically, along the direction where buoyancy flow varies significantly. The coupling between solid fuel and gaseous flame is sensitive to such buoyancy flow variations, making scalability even more challenging. By nature, buoyancy flow is caused by a density gradient in a gravity field. By systematically varying these phenomena, buoyancy flow can be manipulated. First, the effect of density will be studied by varying pressure and diluents of ambient gas in a combustion chamber. Second, the effect of hyper-gravity will be studied using a 17.7m-diameter centrifuge. Experiments will be augmented by calibrated numerical modeling. The small-scale data, where buoyancy flow is artificially enhanced, will be compared to large-scale data from collaborators, where buoyancy flow is naturally up-scaled with fire size. Dimensional analysis will be performed to identify the invariant dimensionless variable groups. Finally, a new scaling model will be proposed to bridge small and large fires by incorporating buoyancy flow. This will allow creation of fire models that make fewer assumptions than ever before. This will also dramatically increase the applicability of lessons from lab-scale experiments as well as allowing re-interpretation of past reduced-scale experiments.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.

该项目将研究火灾行为如何随规模而变化。实验室规模的测试通常用于基础研究和技术标准中，以表征材料的燃烧行为。但是，从小型实验室量表转变为在结构或森林火灾中发现的较大的现实世界尺度时，关键的火灾行为会发生变化。这种可伸缩性问题是消防科学的长期挑战，它限制了实验室测试的普遍性。填补此知识差距将提高标准安全测试的相关性，并导致更安全的结构和产品。最终，这将为社会节省生命，金钱和财产。该项目采用实验，数值模拟和理论模型来控制，研究和预测各种尺度的火灾行为。重点将放在一种称为浮力流的现象上，该现象随规模而变化很大。开发的缩放模型将根据行业合作者维护的现实世界测试数据库进行验证。该项目还将有助于培养下一代的学术和行业领导者。这将通过互动式公开展示火力动力学和促进大学课程的技术标准来实现。影响火灾可伸缩性的关键因素之一是浮力流。该项目将重点关注浮力流对固体上向上的火焰的影响。在这种火灾情况下，燃料样品沿浮力流差异很大的方向垂直定向。固体燃料和气态火焰之间的耦合对这种浮力流量的变化很敏感，从而使可伸缩性更具挑战性。从本质上讲，浮力流是由重力场中的密度梯度引起的。通过系统地改变这些现象，可以操纵浮力流。首先，将通过燃烧室中环境气体的变化压力和稀释剂来研究密度的效果。其次，将使用17.7m直径的离心机研究超级重力的效果。实验将通过校准的数值建模来增强。将浮力流人为增强的小规模数据将与合作者的大规模数据进行比较，在该数据中，浮力流量自然会以火灾大小缩小。将进行维数分析以识别不变的无量纲变量组。最后，将提出一种新的缩放模型，通过合并浮力流量来弥合大小火。这将允许创建比以往任何时候都更少假设的火灾模型。这还将大大提高实验室规模实验的课程的适用性，并允许重新解释过去的减少尺度实验。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛影响的审查标准来通过评估来获得支持的。