The building cross-section shape significantly affects the flow characteristics around buildings, especially the recirculation region behind the high-rise building. Eight generic building shapes including square, triangle, octagon, T-shaped, cross-shaped, #-shaped, H-shaped and L-shaped are examined to elucidate their effects on the flow patterns, recirculation length L and areas A using computational fluid dynamics (CFD) simulations with Reynolds-averaged Navier-Stokes (RANS) approach. The sizes and positions of the vortexes behind the buildings are found to be substantially affected by the building shapes and subsequently changing the recirculation flows. The recirculation length L is in the range of 1.6b–2.6b with an average of 2b. The maximum L is found for L-shaped building (2.6b) while the shortest behind octagon building (1.6b). The vertical recirculation area A_v is in the range of 1.5b²–3.2b² and horizontal area A_h in 0.9b²–2.2b². The L, A_v and A_h generally increase with increasing approaching frontal area when the wind direction changes but subject to the dent structures of the #-shaped and cross-shaped buildings. The area-averaged wind velocity ratio (AVR), which is proposed to assess the ventilation performance, is in the range of 0.05 and 0.14, which is around a three-fold difference among the different building shapes. The drag coefficient parameterized by A_h varies significantly, suggesting that previous models without accounting for building shape effect could result in large uncertainty in the drag predictions. These findings provide important reference for improving pedestrian wind environment and shed some light on refining the urban canopy parameterization by considering the building shape effect.

建筑物横截面形状显着影响建筑物周围的流动特性，特别是高层建筑后面的再循环区域。使用计算流体检查了八种通用建筑形状，包括正方形、三角形、八边形、T 形、十字形、# 形、H 形和 L 形，以阐明它们对流动模式、再循环长度 L 和面积A的影响使用雷诺平均纳维-斯托克斯 (RANS) 方法进行动力学 (CFD) 模拟。人们发现建筑物后面涡流的大小和位置很大程度上受到建筑物形状的影响，并随后改变了再循环流。再循环长度L在1.6b - 2.6b范围内，平均为2b。L 形建筑 (2.6 b ) 的L最大，而八边形建筑 (1.6 b ) 的 L最小。垂直再循环面积A _v在1.5 b ² –3.2 b ²范围内，水平面积A _h在0.9 b ² –2.2 b ^{2 范围}内。风向变化时，L、A v_和A h_{一般随着接近锋面面积的增大而增大，但受#字形和十字形建筑物凹进结构的影响。}用于评估通风性能的面积平均风速比（AVR）在 0.05 至 0.14 之间，不同建筑形状之间的差异约为三倍。由A _h参数化的阻力系数变化很大，这表明以前的模型没有考虑建筑物形状效应可能会导致阻力预测存在很大的不确定性。这些研究结果为改善行人风环境提供了重要参考，并为考虑建筑形状效应的细化城市冠层参数化提供了参考。