悬索桥吊索非定常气动自激力试验

Experiment on Wake-induced Unsteady Aerodynamic Forces for Hangers of Suspension Bridges

为了研究悬索桥吊索尾流索股的非定常气动力,制作表面光滑的吊索双索股刚性节段模型,采用HD-2风洞实验室自主研发的强迫振动装置重现双索股吊索尾流弛振现象,进行尾流索股2个自由度耦合振动状态下的横风向和顺风向测力试验,得到振动状态下尾流索股的气动升力和气动阻力时程。采用激光位移计同步测量2个方向的位移时程,识别尾流索股的8个相关气动导数,研究不同工况下气动导数随量纲一风速的变化规律,并验证采用气动导数拟合得到的非定常气动力的准确性。研究结果表明:尾流索股的气动刚度项系数H*4,H*6在高风速下会出现较大的正值,引起横风向运动气动负刚度,对尾流索股运动起放大作用;气动刚度项系数P*4,P*6仅在部分工况下引起气动负刚度;8个气动导数共同作用改变尾流索股的椭圆形运动轨迹;采用气动导数拟合得到的气动力与风洞试验测得的气动力大小吻合良好,可以利用气动导数对尾流索股的气动刚度力和气动阻尼力展开进一步研究。

Wake galloping is a kind of large amplitude vibration of the hangers always observed on large-span suspension bridges.In order to investigate the unsteady aerodynamic forces on the strand in the wake,two smooth ridge circular cylinder models were made and tested in the wind tunnel tests to measure the aerodynamic forces on the test model by a forced vibration system developed by HD-2 wind tunnel,on which the wake galloping reappeared.The lift and drag force histories,together with the displacement histories,were directly measured in the wind tunnel tests.Eight relative aerodynamic derivatives of the strand in the wake were simultaneously identified.The relationships between eight aerodynamic derivatives and reduced wind velocity in different cases are discussed,and the accuracy of unsteady aerodynamic forces integrated by aerodynamic derivatives is proved.The results show that the aerodynamic stiffness terms H＊4 and H＊6 have quite large positive values under high wind speed,and could cause negative aerodynamic stiffness in across-wind direction and enlarge the vibration amplitude of the strand.The aerodynamic stiffness terms P＊4 and P＊6 only have positive values in few cases.The wake-inducedellipse movement trajectories of the strand in the wake are determined by eight aerodynamic derivations.The unsteady aerodynamic forces obtained through aerodynamic derivatives agree well with that tested directly.The aerodynamic derivatives could be utilized to determine aerodynamic stiffness forces and aerodynamic damping forces for further investigation on wake galloping.