Building-façade-mounted appurtenances are found to be effective for reducing wind loads on high-rise buildings. In this study, large eddy simulations (LES) are performed to investigate the effects of windward-face-mounted ribs on aerodynamic forces acting on a square cylinder of width D under smooth flow. The flow fields, wind pressure distributions and aerodynamic forces on different models are examined to clarify the underlying mechanism of the mitigation of wind load caused by vertical ribs. It is found that local recirculation forms in the front corner region, which greatly influences the flow separation and modifies the behavior of shear-layer flow. Three typical flow patterns around cylinders with different rib depths d are identified: full separation flow (0<d/D ≤ 0.105), periodic attachment flow (0.105<d/D ≤ 0.12), and steady attachment flow (d/D > 0.12). The wake vortex structures, vortex shedding frequency and wind pressure distribution are significantly different under these three flow patterns. The flow field changes result in remarkable mitigation of mean drag ${\bar{C}}_d$ and fluctuating lift C'_l. Optimal combinations of location b and depth d of ribs are also investigated. In these optimal cases, the shear layer first separates from the rib's leading edge and then passes by the cylinder's leading edge. The maximum reduction ratios of ${\bar{C}}_d$ and C'_l reach 50% and 86%, respectively, when d/D = 0.12 and b/D = 0.10. An empirical configuration equation of the vertical ribs is finally proposed by fitting results of optimal combinations.

人们发现，安装在建筑立面上的附属物可有效减少高层建筑的风荷载。在这项研究中，进行了大涡模拟（LES），以研究迎风面安装的肋对顺畅流动下作用于宽度D的方形圆柱体上的空气动力的影响。检查了不同模型上的流场，风压分布和空气动力，以阐明减轻竖向肋引起的风荷载的潜在机理。发现在前拐角区域形成局部再循环，这极大地影响了流分离并改变了剪切层流的行为。确定了三种不同肋深d的圆柱体周围的典型流型：全分离流（0 < d/ d  ≤0.105），周期附着流（0.105 < d / d  ≤0.12），和稳定的连接流（d / d  > 0.12）。在这三种流型下，尾流涡旋结构，涡旋脱落频率和风压分布明显不同。流场变化导致平均阻力的显着缓解${\stackrel{〜}{C}}_d$和波动电梯C”_升。还研究了肋骨的位置b和深度d的最佳组合。在这些最佳情况下，剪切层首先与肋的前缘分离，然后经过圆柱的前缘。最大减少率${\stackrel{〜}{C}}_d$当d / D  ＝ 0.12和b / D  ＝ 0.10时，C ₁和C _1分别达到50％和86％。最后通过拟合最佳组合的结果，提出了竖向肋的经验构型方程。