湍流强度对桥梁断面气动力特性的影响

Effect of turbulence intensity on aerodynamic force of bridge girder

摘要:

桥梁结构处于大气边界层中,由于断面外形复杂、折点较多,其绕流常呈现复杂的流动分离和再附着状态,应评估来流湍流对桥梁断面气动特性的影响。基于节段模型测压风洞试验,获取了均匀流场和3种格栅湍流场下模型表面平均和脉动压力分布,评估了桥梁断面气动力特性的改变,分析了不同风场下断面流动分离再附着的变化。研究发现:湍流显著改变桥梁断面前缘（特别是零度和正攻角时上表面和负攻角时下表面）的分离和再附着特性,进而影响桥梁整体断面的气动力特性；随着湍流强度增加,前缘分离点的平均压力系数的幅值增大,而再附着点向上游移动；湍流强度对分离和再附着的影响程度随着风攻角的增大而变得显著；三分力系数在小风攻角时受湍流强度影响较小,在大风攻角下湍流强度的影响较大,变化的主要原因是断面前缘的压力分布变化。

Abstract:

Due to the complex profile of a bridge girder with several corners, the flow around its section exhibits obvious flow separation and reattachment phenomena. It is necessary to assess how atmospheric turbulence affects aerodynamic force. A segment model pressure wind tunnel test was carried out, and the mean and fluctuating pressure distributions in a uniform wind field and three grid-generated wind fields were obtained. The changes in the aerodynamic forces were evaluated, and the effects of turbulence on flow separation and reattachment phenomena were analyzed. Results showed that turbulence significantly changed the separation and reattachment characteristics of the section at the leading edge (especially the upper surface at zero and positive attack angles and the lower surface at negative attack angles), which in turn affected the aerodynamic characteristics of the bridge section. As the turbulence intensity increased, the amplitude of the mean pressure coefficient at the separation point near the leading edge increased, while the reattachment point moved upstream. The influence of turbulence intensity on separation and reattachment became more noticeable with the increase in the wind attack angle. The force coefficient was more affected by turbulence intensity at a high attack angle than at a small attack angle, mostly because of the pressure changes at the leading edge.