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湍流强度对圆角方柱气动特性的影响
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Abstract:
圆角方柱在实际工程中应用越来越广泛，但由于圆角化后的方柱绕流呈现复杂的流动分离和再附着状态，而且实际工程中的结构处于大气边界层中，应评估来流湍流对圆角方柱风荷载特性的影响。针对标准方柱和圆角率为0.15和0.3的圆角方柱在自由流场和3种格栅湍流场下进行了试验研究，对湍流强度在不同入射角下对圆角方柱气动特性的影响开展深入分析。研究发现，湍流显著改变圆角方柱的分离和再附着特性，进而影响其气动力特性；湍流增强流体动能交换和混合，导致小入射角下圆角方柱前缘吸力增加并形成分离泡；湍流促进侧表面流体重新附着，在靠近后缘圆角处再分离，减小平均阻力系数，增加旋涡脱落频率；随湍流强度增加，平均升力系数由正转负，并随入射角变化呈“V”型趋势，且随着入射角增大，下侧壁面流体逐渐完全分离，而上侧壁面流体呈现重新结合特征，进一步改变圆角方柱的整体气动性能。
Square cylinders with rounded corners are increasingly used in practical engineering. However, due to the complex flow separation and reattachment states around these cylinders after rounding the corners, and the fact that structures in real engineering are situated within the atmospheric boundary layer, it is necessary to assess the impact of incoming turbulence on the wind load characteristics of square cylinders with rounded corners. Experimental studies were conducted on standard square cylinders and square cylinders with rounded corners (corner radius ratios of 0.15 and 0.3) in free flow and three grid-generated turbulent fields. An in-depth analysis was carried out on the influence of turbulence intensity on the aerodynamic characteristics of square cylinders with rounded corners at different angles of incidence. The research found that turbulence significantly alters the separation and reattachment characteristics of square cylinders with rounded corners, thereby affecting their aerodynamic force characteristics. Turbulence enhances fluid kinetic energy exchange and mixing, leading to increased suction at the leading edge and the formation of separation bubbles at small angles of attack. It promotes fluid reattachment on the side surfaces and causes re-separation near the rounded trailing edge, reducing the mean drag coefficient and increasing the vortex shedding frequency. As turbulence intensity increases, the mean lift coefficient changes from positive to negative and exhibits a “V-shaped” trend with varying angles of attack. Moreover, as the angle of attack increases, the fluid on the lower wall surface gradually separates completely, while the fluid on the upper wall surface shows reattachment characteristics, further altering the overall aerodynamic performance of the square cylinder with rounded corners.
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