Surface-mounted bluff bodies immersed in deep turbulent boundary layers

在过去的二十年里，由于极端天气造成的经济和保险损失不断增加。这与人口增长、人口向大城市迁移以及气候变化有关。减少灾难性损失研究所（ICLR）正在努力制定减灾战略，特别关注地震、洪水、极端大风和野火。这项建议涉及减轻极端风，特别是飓风和龙卷风的影响。在龙卷风中减轻风荷载的主要挑战是在龙卷风中建立空气动力学很大程度上是未知的。基本方法是采用“直线”风（如飓风）的风荷载，并应用乘法系数来采用龙卷风的风荷载。这项研究面临的挑战是将与龙卷风相关的旋涡结构的影响与其他湍流分离开来，后者既影响大气边界层的直线风，也影响龙卷风。该提案的目的是为了更好地理解湍流的作用，以支持ICLR确定龙卷风风荷载的目标。更具体地说，将使用时间分辨粒子图像测速技术来测量由深湍流边界层中三维表面安装的钝体产生的尾流的速度。速度数据将被分析，以发展对建筑空气动力学的科学理解，并有可能导致更可靠的预测模型的发展，这将使ICLR能够制定更有效的策略来减轻极端风的影响，特别是飓风和龙卷风。这项研究的结果还将通过更精确地定义湍流的作用来帮助ICLR定义龙卷风中的风载荷。

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.