Understanding Particle Scale Motion Initiation Physics for Loose-laid Building Rooftop Aggregates in Severe Windstorms

了解强风暴中松散建筑屋顶骨料的粒子尺度运动引发物理学

• 批准号: 1760999
• 负责人: Nigel Kaye
• 金额: $ 37万
• 依托单位: Clemson University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1760999&HistoricalAwards=false
• 关键词: Understanding; Particle; Scale; Motion; Initiation

Loose-laid aggregate is commonly used on building rooftops either as ballast or as part of increasingly popular green roof systems. However, the individual stones can become airborne during severe storms such as hurricanes, tornadoes, and thunderstorms. Once airborne, the particles can damage buildings downwind and destabilize the roof from which they are removed. The mechanics of exactly how the wind lifts up individual particles is poorly understood, particularly in the complex wind flow around and over a building. This research will combine state-of-the-art, large-scale wind tunnel testing with detailed computational modeling to establish the aerodynamic forces acting on individual particles as they become airborne. The knowledge generated from this research will enable engineers to design building roof systems that are significantly less prone to aggregate blow-off, thus creating safer buildings and surroundings during severe storms. Learning modules based on the research findings will be developed for undergraduate and graduate fluid mechanics courses. The research also will be used as a platform in Clemson University's EMAG!NE program to engage high school science and math students in outreach activities related to windstorms and other natural hazards. The research team will include a diverse group of graduate and undergraduate students working with faculty in South Carolina and Florida. Data from this project will be archived and made publicly available in the NSF-supported Natural Hazards Engineering Research Infrastructure (NHERI) Data Depot (https://www.DesignSafe-ci.org/). This research will, for the first time, elucidate the physics of loose-laid particle motion initiation in a non-uniform, highly separated turbulent flow. The combination of large- and full-scale wind tunnel experimentation, Large Eddy Simulation (LES) computational modeling, and model validation using physical tests will produce a comprehensive understanding of the mechanics of particle motion initiation. This project will use the NSF-supported NHERI Wall of Wind facility at Florida International University for experimentation. The experiments and simulations will produce data on the surface shear stress distribution over a roof surface and its correlation with the pressure field. The research approach of examining particle scale loading and developing physics-based criteria for motion initiation can transform the understanding of other scour problems and mark a significant departure from models that assume uniform flow. This research will move away from empirical approaches to scour that assume shear stress and horizontal aerodynamic drag as the dominant factors for the motion initiation process. By modeling the individual physical processes that, when coupled, result in particle motion, the research can be extended to other erosion problems in unsteady separated flows. The mitigation study on parapets will result in a comprehensive data set on the load changes that result from placing parapets above flat roofs. Combined with the LES modeling, this research will improve the understanding of the role of parapets in building aerodynamics and can lead to safer building designs.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.

松散铺设的骨料通常用于建筑物屋顶，作为压载物或作为日益流行的绿色屋顶系统的一部分。然而，在飓风、龙卷风和雷暴等严重风暴期间，个别石头可能会在空中漂浮。一旦空气中的颗粒，可以破坏建筑物顺风和不稳定的屋顶，他们从删除。人们对风是如何将单个粒子卷起的机制知之甚少，特别是在建筑物周围和上方的复杂风流中。这项研究将结合联合收割机最先进的，大规模的风洞试验与详细的计算建模，以建立作用在单个颗粒上的空气动力，因为他们成为空中。从这项研究中获得的知识将使工程师能够设计出不太容易发生聚集物脱落的建筑屋顶系统，从而在严重风暴期间创造更安全的建筑物和环境。 基于研究结果的学习模块将被开发用于本科和研究生流体力学课程。这项研究也将被用作克莱姆森大学埃马克的平台！NE计划让高中科学和数学学生参与与风暴和其他自然灾害有关的外联活动。研究团队将包括一个多元化的研究生和本科生群体，他们与南卡罗来纳州和佛罗里达的教师一起工作。 该项目的数据将在NSF支持的自然灾害工程研究基础设施（NHERI）数据库（https：//www.DesignSafe-ci.org/）中存档并公开提供。这项研究将首次阐明在非均匀、高度分离的湍流中松散颗粒运动起始的物理机制。大型和全尺寸风洞实验，大涡模拟（LES）计算建模和模型验证使用物理试验相结合，将产生一个全面的了解粒子运动启动的机制。 该项目将使用美国国家科学基金会支持的佛罗里达国际大学的NHERI风墙设施进行实验。实验和模拟将产生关于屋顶表面上的表面剪应力分布及其与压力场的相关性的数据。 检查颗粒尺度加载和开发基于物理的运动启动标准的研究方法可以改变对其他冲刷问题的理解，并标志着与假设均匀流的模型的显著偏离。这项研究将远离经验方法冲刷假设剪切应力和水平气动阻力的运动启动过程的主导因素。通过对单个物理过程进行建模，当耦合时，导致颗粒运动，研究可以扩展到非定常分离流中的其他侵蚀问题。对女儿墙进行的缓解研究将产生一套关于在平屋顶上放置女儿墙所引起的负荷变化的全面数据。结合LES建模，这项研究将提高对女儿墙在建筑空气动力学中作用的理解，并可以导致更安全的建筑设计。该奖项反映了NSF的法定使命，并被认为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来支持。

项目成果

A stochastic model for the aerodynamics of irregularly shaped gravel

不规则形状砾石空气动力学的随机模型

• DOI: 10.1016/j.jweia.2021.104782
• 发表时间: 2021
• 期刊: Journal of Wind Engineering and Industrial Aerodynamics
• 影响因子: 4.8
• 作者: Ahsanullah, Md Safwan;Kaye, Nigel B.;Bridges, William C.
• 通讯作者: Bridges, William C.

Smooth roof pressure tests:Roof gravel motion initiation

平滑顶板压力测试：顶板砾石运动引发

• DOI: 10.17603/ds2-vsbn-t326
• 发表时间: 2024
• 期刊: Designsafe-CI
• 作者: Kaye, Nigel;Ahsanullah, Md Safwan;Conklin, Walter;Chen, Dejiang;Irwin, Peter;Gan Chowdhury, Arindam;Erwin, James
• 通讯作者: Erwin, James

Gravel roof pressure and shear stress measurements:Roof gravel motion initiation

砾石顶板压力和剪应力测量：顶板砾石运动引发

• DOI: 10.17603/ds2-s3fm-2870
• 发表时间: 2024
• 期刊: Designsafe-CI
• 作者: Kaye, Nigel;Ahsanullah, Md Safwan;Conklin, Walter;Chen, Dejiang;Irwin, Peter;Gan Chowdhury, Arindam;Erwin, James
• 通讯作者: Erwin, James

Gravel removal tests:Roof gravel motion initiation

砾石清除测试：屋顶砾石运动引发

• DOI: 10.17603/ds2-xt1n-w752
• 发表时间: 2024
• 期刊: Designsafe-CI
• 作者: Kaye, Nigel;Ahsanullah, Md Safwan;Conklin, Walter;Chen, Dejiang;Irwin, Peter;Gan Chowdhury, Arindam;Erwin, James
• 通讯作者: Erwin, James