基于强迫振动装置的拉索和水线气动力试验

Experimental Investigation on Aerodynamic Forces on Stay Cable and Rivulet by Using Forced Vibration System

为了研究斜拉索风雨激振中拉索和水线上的气动力,制作了直径为350mm的拉索模型,采用强迫振动装置,对粘贴水线的二维拉索进行了5种工况下的测压风洞试验。系统研究了水线的存在、模型竖向和扭转振动对拉索和水线的平均风压系数、脉动风压系数、平均气动力系数、脉动升力系数功率谱等的影响,并对准定常理论在风雨激振理论分析中的适用性进行了验证。结果表明:准定常理论能反映拉索和水线气动力的主要特征;拉索竖向振动和水线周向摆动基本不影响拉索和水线的平均气动力系数,拉索平均升力系数在60°风攻角处发生突降;水线的周向摆动对脉动气动力的影响很大,远大于拉索竖向振动的影响;水线的存在不仅使水线附近的风压系数发生突变,而且还降低了旋涡脱落频率。

Abstract： To investigate the aerodynamic forces acting on the stay cable and the rivulet during rain-wind induced vibrations, a cable model with a diameter of 350 mm was made. And 5 cases of wind tunnel tests were carried out to measure wind pressures on the cable and rivulet by using forced vibration system. The effects of the rivulet and the test model vibrations on the mean and fluctuating wind pressure coefficients, the mean aerodynamic force coefficients and the power spectral density of fluctuating lift coefficients were systematically studied. Moreover, the validity of quasi-steady theory in rain-wind induced vibrations was checked out. The results indicate that quasi-steady theory can reflect the main characteristics of the wind forces on the cable and the rivulet; the oscillation of the rivulet and vertical vibration of the cable do not change their mean wind force coefficients, and there is a fast drop of mean lift coefficient at the attack angle of 60~; the oscillation of the rivulet on the cable surface heavily affects the fluctuating aerodynamic force coefficients, while the vertical vibration of the cable has a little influence; furthermore, the presence of the rivulet decreases the frequency of vortex shedding.