中央开槽宽度对箱梁涡振特性的影响机理

设置中央开槽的箱梁通常具有良好的颤振稳定性，但该类箱梁在大攻角来流作用下的涡振性能尚不明确. 采用数值模拟方法，针对某大跨度桥梁的流线型箱梁断面，分析了5种不同中央开槽宽度箱梁的流场特性和涡振稳定性能，探究了大攻角下中央开槽宽度变化对箱梁涡振性能的影响规律，并根据静态和动态流场的变化，系统讨论了相应的气动机理. 研究结果表明:在?10°～10° 风攻角范围内，封闭箱梁的阻力系数始终最小，而其升力系数绝对值则普遍大于开槽箱梁；中央开槽宽度（L）对箱梁涡振性能影响显著，箱梁涡振振幅随着开槽宽度的增大而减小，L/B（B为箱梁宽度）由0变化至0.20，涡振振幅变化幅度达到40.9%；开槽宽度的变化会影响箱梁上表面大旋涡的运动以及箱梁中央区域来流分离程度，进而改变箱梁的涡振振幅. 

Effect Mechanism of Central Slot Width on Vortex-Induced Vibration Characteristics of Streamlined Box Girders

The streamlined box girders with central slots usually have good flutter stability, but the vortex-induced vibration (VIV) performance of such box girders at large angles of attack is not clear. For the streamlined box girder section of a long-span bridge, the flow field characteristics and VIV performances of the box girders with five different central slot widths were analyzed by numerical simulation method. Then the influence law of the central slot width on the VIV performances of box girder at large angles of attack were investigated, and the corresponding aerodynamic mechanisms were discussed systematically according to the changes of static and dynamic flow fields. The results show that the drag coefficient of the closed box girder is always the smallest for the wind attack angles in the range of ?10°~10°, while the lift coefficient of the closed box girder is generally larger than that of the slotted box girder. The width of central slot has a significant effect on the VIV performance of the box girder, and the VIV amplitude of box girder decreases with an increase in slot width. When L/B changes from 0 to 0.20, the VIV amplitude varies by 40.9%. The change of the slot width will affect the movement of large vortices on the upper surface of a box girder and also affect the separation degree of incoming flow in the central region of the box girder, making VIV amplitude of streamlined box girder change.