Investigation of local-scale extreme convective wind events and their interaction with building structures in urban areas

强对流阵风可能达到的风速远远超过天气尺度的冬季风暴。与此相关的是对建筑物、关键基础设施或农作物的相当大的破坏潜力。由于深厚湿对流的局地尺度性质，有关对流阵风的概率、空间范围和最大速度的基本信息既不能直接从数值模式数据中获得，也不能从具有必要空间代表性的现有观测站的数据中估计。此外，单站的点测量不能再现与建筑结构相互作用引起的阵风的额外放大。因此，强对流阵风在建筑物和结构的风荷载规范和标准中的代表性不足，这些规范和标准通常基于气象站获得的时间序列。这导致相当缺乏知识，在几个尺度，从积云内的阵风的产生，其特性和气候学的流量传播的建筑结构，包括impactions.The总体目标的拟议项目是减少这种知识差距的时间和空间的高分辨率观测在几个尺度，并估计它们对城市结构的影响。在该项目的气象部分，来自不同观测系统和网络（测量桅杆，激光雷达，雷达）的数据被合并和统计分析，目的是根据主要气象条件调查垂直下沉气流和水平阵风之间的关系。最大阵风风速与不同的对流系统的估计应用适当的经验参数化方案的观测。根据这些方法和所获得的结果，气候学，包括强对流阵风的概率，将从长期的高分辨率再分析数据中得出。对流阵风应在提案的流体力学部分详细研究，目的是通过大气边界层风洞内的实际实验，增进关于下沉气流和阵风与典型城市建筑物相互作用的基本知识。为此，风洞试验段应配备阵风发生器，以产生预定持续时间、范围和倾斜度的阵风。嵌入水平流场中的阵风应从移动源释放，以模拟规定建筑配置上的真实风荷载。阵风以倾斜的轨迹撞击地面，这可以看作是阵风速度、对流系统速度和基流速度的叠加。应使用时间分辨PIV系统和高灵敏度测压技术，以高时间和空间分辨率研究阵风动力学和相互作用。

Severe convective gusts may reach wind speeds that exceed by far those related to synoptic-scale winter storms. Associated with this is a considerable damage potential for buildings, critical infrastructure, or crops. Due to the local-scale nature of deep moist convection, essential information concerning probability, spatial extent and maximum speeds of the convective gusts can neither be obtained directly from numerical model data nor estimated from data of available observation stations with the necessary spatial representativeness. Moreover, point measurements at single stations cannot reproduce the additional amplification of gusts caused by the interaction with built-up structures. Therefore, severe convective gusts are underrepresented in the wind loading codes and standards for buildings and structures, which are usually based on time series obtained from meteorological stations. This leads to a considerable lack of knowledge over several scales, from the generation of the gusts within cumulus clouds over their characteristics and climatology to the flow propagation over built-up structures including the impacts.The overall objective of the proposed project is to reduce this knowledge gap by temporally and spatially high-resolving observations over several scales and to estimate the impact they exert on urban structures. In the meteorological part of the project, data from different observation systems and networks (measuring masts, Lidar, Radar) are combined and statistically analyzed with the aim to investigate the relation between vertical downdrafts and horizontal gusts depending on the prevailing meteorological conditions. Maximum gust wind speeds related to different convective systems are estimated by applying appropriate empirical parameterization schemes to the observations. Based on these methods and the obtained results the climatology including the probability of severe convective gusts shall be derived from high-resolution reanalysis data over a long-term period. Convective gusts shall be investigated in detail in the fluid mechanical part of the proposal, which aims at improving the basic knowledge about the interaction of downdrafts and gusts with typical urban built-up structures by realistic experiments within an atmospheric boundary layer wind tunnel. For this, a wind tunnel test section shall be constructed with a gust generator, which generates gusts of pre-defined duration, extent, and tilt. Embedded in a horizontal flow field, the gusts shall be released from a moving source in order to simulate realistic wind loading on defined building configurations. Typically, the gust hits the ground with an oblique trajectory, which can be conceived of as the superposition of gust velocity, velocity of convective system and base flow velocity. The gust dynamics and interaction shall be investigated with high temporal and spatial resolution using a time-resolved PIV system and highly sensitive pressure tapping technique.