Model to Full-Scale Validation of Peak Pressure Mechanisms in Buildings that Cause Cladding Failures and Windstorm Damage

风工程的基础是需要了解和模拟土木工程基础设施(例如建筑物)上风荷载的流动分离的基本物理原理，因为与任何其他工程领域不同，这些结构不是原型，而是几乎完全依赖于大幅缩减长度和较低风速尺度的风洞试验。由于测量结构的复杂性和观察设计事件所需的长时间，风洞结果很少得到验证。大多数对建筑物的风暴破坏都是在建筑物上观察到非常高的吸入压力的位置上的覆层破裂开始的，通常是在气流在峰值和波动压力下与结构分离的角落和边缘附近。风洞已成为获取各种类型结构风荷载的普遍工具，但在边界层风洞中模拟的低层结构屋顶分离流区产生的峰值压力和脉动压力之间的差异与现场观测结果之间的差异一直是有报道的。该项目将利用美国国家科学基金会支持的佛罗里达国际大学自然危害工程研究基础设施(NHERI)风墙(WOW)设施，在接近全尺寸的情况下调查导致这些极高吸力的流动机制，以确定当前的小规模风洞测试是否能够重现它们，并确定哪些流入流动特征对导致高吸力最关键。从分离流的参数研究中，将分离出对开发这些峰值压力至关重要的建模标准，并将确定在典型风洞研究中以缩小尺度模拟这些峰值压力的能力。通过这种方式，可以验证传统风洞测试的可信度，并改进和验证现有的实验程序。这些详细的知识将为风洞测试和通用风洞数据提供更大的信心，供工程师使用，并最终转化为减少风暴对民用基础设施的破坏。该项目将培养一名博士后研究员；与纽约州特洛伊的特洛伊中学合作，举办一项全国未来城市竞赛，以打造“多风的城市”；并将研究成果纳入风工程研究生课程和该机构关于进步建筑的贝德福德计划。该项目旨在提供分离剪切层的流动物理的力学表征，以及进场流动的全湍流谱对分离附近的峰值和脉动压力产生的影响。从基本流体力学的观点来看，有必要了解几十年来对分离流的基础研究的适用性和可扩展性，这些研究主要是在全尺寸的民用基础设施上进行的，主要是在低雷诺数和低湍流的情况下进行的。利用WOW设备，大型钝体将在很高的雷诺数下暴露在各种湍流结构和强度下，并将同时研究流场和压力场。本项目将研究为什么在自由流中同时存在小尺度(高频)和大尺度(低频)湍流结构以在分离区内产生最大量级压力，以及这些结构如何从模型尺度扩展到全尺度。对这种正则流动现象在高雷诺数下的非定常特性进行系统的测量，将有助于流体力学领域理解一大类流动现象的模拟局限性。此外，本研究的结果将为计算流体动力学程序的验证提供一个基准。随着对大型物理长度尺度和接近全尺寸雷诺数的峰值和脉动压力产生机理的深入了解，将提供关于适当的流场物理模型的指南和建议；此外，还将开发风洞结果的修正系数。该项目的数据将被存档，并在国家医疗保险研究所数据仓库(https://www.designsafe-ci.org).)中可用

Fundamental to wind engineering is the need to understand and model the underlying physics of flow separation of wind loading on civil infrastructure (e.g., buildings), as unlike any other engineering domain, these structures are not prototyped but rely almost exclusively on wind tunnel tests at vastly reduced length and lower velocity scales. Wind tunnel results are rarely validated due to the complexity of instrumenting the structure and the long duration required to observe design events. Most windstorm damage to buildings is initiated with cladding failures at locations where very high suction pressures are observed on the building, typically near corners and edges where the flow separates from the structure under peak and fluctuating pressures. Wind tunnels have become ubiquitous for obtaining wind loads on all types of structures, but discrepancies between peak and fluctuating pressures generated in the separated flow regions on roofs of low-rise structures modeled in boundary layer wind tunnels and observed in the field have been long-reported. This project will investigate the flow mechanisms that cause these very high suctions at near full-scale using the NSF-supported Natural Hazards Engineering Research Infrastructure (NHERI) Wall of Wind (WOW) facility at Florida International University to determine if current small-scale wind tunnel tests are able to reproduce them and to determine which incoming flow characteristics are most critical in causing the high suctions. From parametric studies of separating flows, the modeling criteria critical in developing these peak pressures will be isolated and the ability to simulate them at reduced scales in typical wind tunnel studies will be ascertained. In this way, confidence in traditional wind tunnel testing can be validated and current experimental procedures improved and verified. This detailed knowledge will provide greater confidence in wind tunnel testing and generic wind tunnel data for engineers to use, and ultimately translate to reduced windstorm damage to civil infrastructure. This project will train a postdoctoral researcher; work with the Troy Middle School in Troy, New York, on a National Future Cities Competition for a "windy city;" and incorporate the research outcomes into a graduate course on wind engineering and the institution's Bedford Program on progressive buildings. This project aims to provide a mechanistic characterization of the flow physics of separating shear layers, and the effect of the full turbulence spectrum of the approach flow on peak and fluctuating pressure generation in the vicinity of separation. From a fundamental fluid mechanics viewpoint, there is a need to understand the applicability and scalability of decades of fundamental research on separated flows, which has been performed predominately at low Reynolds Numbers and in low turbulence flows, on full-scale civil infrastructure. Using the WOW facility, a large-scale bluff body will be exposed to a range of turbulent structures and intensities at very high Reynolds Numbers, and flow and pressure fields will be studied simultaneously. This project will investigate why the presence of both small-scale (high frequency) and large-scale (low frequency) turbulent structures in the freestream are needed concurrently to cause the largest magnitude pressures within the separation region and how these scale from model to full-scale. A set of systematic measurements of the unsteady characteristics of this canonical flow phenomenon at high Reynolds Numbers will be beneficial to the fluid mechanics community to understand the simulation limitations of a wide class of flow phenomenon. In addition, the results of this research will provide a benchmark for validation of computational fluid dynamics codes. With an advanced understanding of mechanics of the generation of peak and fluctuating pressures at large physical length scales and near full-scale Reynolds Numbers, guidelines and recommendations on appropriate physical modelling of the flow field will be provided; additionally, correction factors for wind tunnel results will be developed. Data from this project will be archived and made available in the NHERI Data Depot (https://www.designsafe-ci.org).