地面效应对近流线型断面涡激共振性能的影响

Ground effects on vortex-induced vibrations of a closed box girder

当桥面接近地面时,地面的存在会使断面的绕流情况与远离地面时不同,有可能对主梁在风荷载作用下的静力和动力响应产生不利的影响,而主梁离地高度将成为影响主梁气动性能的重要因素。基于风洞试验和计算流体动力学(CFD)相结合的方法,对存在地面效应的近流线型断面的涡激共振性能进行研究。首先,基于风洞试验获得近流线型断面在两种粗糙度地面、三种风攻角、四种离地高度下的涡激共振区间和振幅及其随离地高度的变化规律,试验结果表明,地面效应会使得涡激共振区间提前但涡激共振幅值有所减小。其次,采用CFD识别各试验工况下的断面的绕流特征、锁定区间和最大振幅,并通过静态和动态流场可视化分析,分析了地面效应对近流线型断面涡激振动的影响机理。

As many existing or under-construction bridges are of lower height from the ground,the ground may have an adverse influence on the aerostatic and aerodynamic performances of bridges under wind loads. Wind tunnel tests and numerical simulations were adopted to study the ground effects on the vortex-induced vibrations of a closed box girder for illustration. The lock-in phenomena of vortex-induced vibrations over a range of wind velocities,the maximum amplitudes and their correlation with the height of the closed box girder apart from the ground under two different ground roughnesses were investigated by wind tunnel tests. The results show that the ground effect makes the vortex-induced phenomena occur in advance. Moreover,CFD( computational fluid dynamic) numerical simulations were carried out to study the lock-in phenomena,the maximum amplitudes and their correlation with the height of the girder under two different ground roughnesses. Through the CFD analysis on the flow fields around the girder,the mechanism of ground effect on the vortexinduced vibrations of closed box girders was described.