Surface-mounted bluff bodies immersed in deep turbulent boundary layers

过去二十年来，极端天气造成的经济和保险损失不断增加，这与人口增长、人口向大城市迁移和气候变化有关。减少灾害损失研究所（ICLR）正在努力制定减灾战略，特别关注地震、洪水、极端风和野火。这项建议涉及减轻极端风，特别是飓风和龙卷风的影响。减轻龙卷风风荷载的主要挑战是，在龙卷风中建造空气动力学在很大程度上是未知的。基本的方法是采用“直线”风（如飓风）的风荷载，并应用倍增因子来采用龙卷风的风荷载。这方面的挑战是将与龙卷风相关的旋转旋涡结构的影响与湍流的其余部分分开，这影响了大气边界层和龙卷风中的直线风。该提案的目标是更好地理解湍流的作用，以支持ICLR定义龙卷风中风载荷的目标。更具体地说，时间分辨粒子图像测速技术将被用来执行由三维表面安装的钝体产生的尾流中的速度测量，该钝体浸没在深湍流边界层中。将对速度数据进行分析，以发展对建筑物空气动力学的科学理解，并可能导致开发更可靠的预测模型，使ICLR能够制定更有效的战略，以减轻极端风的影响，特别是飓风和龙卷风。这项研究的结果也将有助于ICLR通过更精确地定义湍流的作用来定义龙卷风中的风荷载。

There have been ever-growing economic and insured losses due to extreme weather over the past two decades.This is related to population growth, population migration to large cities and climate change. The Institute forCatastrophic Loss Reduction (ICLR) is working to develop mitigation strategy with a particular focus onearthquakes, flooding, extreme wind and wildfire. This proposal relates to mitigating the effects of extremewind, particularly, hurricanes and tornadoes. The primary challenge with mitigating wind loads in tornadoes isthat building aerodynamics in tornadoes are largely unknown. The basic approach is to adopt the wind loads for'straight-line' winds (such as hurricanes), and apply a multiplication factor to adopt them for tornadoes. Thechallenge for this is to separate the effects of the swirling vortical structures associated with tornadoes from therest of turbulence, which affects both straight-line winds in the atmospheric boundary layer and tornadoes.The goal of this proposal is to better understand the role of turbulence, in support of ICLR's objective to definewind loads in tornadoes. More specifically, a time-resolved particle image velocimetry will be used to performvelocity measurements in the wake flow generated by three-dimensional surface-mounted bluff bodiesimmersed in deep turbulent boundary layers. The velocity data will be analyzed to develop scientificunderstanding of building aerodynamics, and potentially lead to the development of more reliable predictivemodels that will enable ICLR to develop more effective strategy for mitigating the effects of extreme wind,particularly, hurricanes and tornadoes. The results from this research will also help ICLR to define wind loadsin tornadoes by defining the role of turbulence more precisely.