Urban block layouts affect both the flow patterns of floodwater and wind in urban built environments and ultimately pedestrian danger within the urban building array. Computational fluid dynamics (CFD) is used to simulate both the floodwater inundation process and the wind-blowing process within three kinds of urban block configurations under a floodwater-wind joint effect, including the lift-up building design, horizontal and vertical building setbacks, and urban open space. The obtained floodwater velocity, depth, and wind speed at the pedestrian level are adopted to quantify the level of pedestrian danger by using the instability threshold formula of a human body. A laboratory flume experiment regarding the stability/instability of a dummy that represents a pedestrian in a quasi-natural state is performed to qualitatively validate the numerical simulation results. Compared to the cuboid or triangular pillar that supports the lift-up building structure, the circular pillar yields the minimum resistance against floodwater and increases the wind speed at the pedestrian level, consequently leading to a large danger zone area. Horizontal building setbacks decrease the pedestrian danger, but vertical building setbacks intricately affect it. The existence of open space within the block decreases pedestrian danger to some extent depending on the location and area of open space. The wind plays the dominant role in triggering pedestrian instability for both the lift-up building design and the horizontal setback case. For both the lift-up building design and the open space configuration, the walking and running speeds of pedestrians decrease much more than the conventional urban block. The results of this study could be referred to by administrators and stakeholders in the design and management of urban building arrays to mitigate pedestrian risk in the content of resilient city management.

中文翻译：

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洪水和风共同作用下抬升建筑设计、建筑后退区和城市开放空间对行人危险性的影响


城市街区布局会影响城市建筑环境中洪水和风的流动模式，并最终影响城市建筑阵列中的行人危险。计算流体力学 （CFD） 用于模拟洪水-风联合效应下 3 种城市街区配置内的洪水泛滥过程和风吹过程，包括抬升建筑设计、水平和垂直建筑退缩区以及城市开放空间。采用获得的行人级别的洪水速度、深度和风速，使用人体的不稳定阈值公式来量化行人的危险程度。对代表准自然状态下行人的假人的稳定性/不稳定性进行了室内水槽实验，以定性验证数值模拟结果。与支撑升降建筑结构的长方体或三角形柱子相比，圆形柱子对洪水的抵抗力最小，并增加了行人层的风速，从而导致较大的危险区域区域。水平建筑后退区减少了行人的危险，但垂直建筑后退区错综复杂地影响了行人危险。街区内开放空间的存在在一定程度上降低了行人的危险，具体取决于开放空间的位置和面积。风在引发行人不稳定性方面起着主导作用，无论是升升式建筑设计和水平后退情况。对于升降式建筑设计和开放空间配置，行人的步行和跑步速度比传统城市街区下降得更多。 在城市建筑阵列的设计和管理中，管理人员和利益相关者可以参考这项研究的结果，以减轻弹性城市管理内容中的行人风险。