Abstract Wind-tunnel experiments were conducted on an elongated bluff body to investigate the effects of leading-edge separation on its vortex shedding and aerodynamic characteristics. Solid wind barriers of various heights were fixed at the leading edge to adjust the flow separation and reattachment. The flow field, particularly the upper-surface boundary layer, was investigated by employing a high-resolution particle image velocimetry (PIV) system. According to the PIV results, it was found that the critical height-to-thickness ratio for the leading-edge separated flow to reattach to the surface is h/t ​= ​0.5. The streamwise length of the reverse flow region increases with an increase in the height of the wind barrier. The effects of leading-edge separation on the vortex evolution and shedding were analysed. As h/t ​≤ ​0.5, the leading-edge separated shear layer is stable and reattaches to the surface. There exists only Karman vortex shedding in the wake when h/t ​≤ ​0.2, while the vortex evolution becomes random when 0.3 ​≤ ​h/t ​≤ ​0.5. However, when h/t ​> ​0.5, the leading-edge separated shear layer becomes unstable, thus resulting in free vortex shedding, convecting downstream, and interacting with the lower shear layer. Moreover, the Strouhal number of the vortex in the wake decreases from h/t ​= ​0 to h/t ​= ​0.5 and then increases from h/t ​= ​0.6 to h/t ​= ​1.0.

中文翻译：

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前缘分离对细长钝体涡脱落及气动特性的影响

摘要 通过风洞实验，研究了细长钝体前缘分离对其涡脱落和气动特性的影响。各种高度的实心风障固定在前缘，以调节气流分离和重新附着。通过采用高分辨率粒子图像测速 (PIV) 系统研究流场，特别是上表面边界层。根据PIV结果，发现前缘分离流重新附着到表面的临界高厚比为h/t=0.5。逆流区域的流向长度随着风障高度的增加而增加。分析了前缘分离对涡旋演化和脱落的影响。由于 h/t ≤ 0.5，前缘分离的剪切层稳定并重新附着到表面。当h/t ≤ 0.2 时，尾流中仅存在卡门涡旋脱落，而当0.3 ≤ h/t ≤ 0.5 时，涡旋演化变得随机。然而，当h/t>0.5时，前缘分离剪切层变得不稳定，从而导致自由涡脱落，向下游对流，并与下剪切层相互作用。此外，尾流中涡旋的 Strouhal 数从 h/t = 0 减少到 h/t = 0.5，然后从 h/t = 0.6 增加到 h/t = 1.0。从而导致自由涡旋脱落，向下游对流，并与较低的剪切层相互作用。此外，尾流中涡旋的 Strouhal 数从 h/t = 0 减少到 h/t = 0.5，然后从 h/t = 0.6 增加到 h/t = 1.0。从而导致自由涡旋脱落，向下游对流，并与较低的剪切层相互作用。此外，尾流中涡旋的 Strouhal 数从 h/t = 0 减少到 h/t = 0.5，然后从 h/t = 0.6 增加到 h/t = 1.0。