斜拉索上水线气动性能的大涡模拟研究

Investigation on aerodynamic characteristics of upper rivulet on stay cable using large eddy simulation

上水线在斜拉索上表面的形成是拉索发生风雨激振的关键因素,目前上水线的形成机理尚不清楚,现有风洞试验方法难以研究作用在上水线上的风致表面摩擦力。采用大涡模拟方法,针对带上水线拉索模型,研究水线处在不同位置时,作用在拉索和上水线上的平均气动力特性,得到作用在上水线上的风致压力和风致表面摩擦力随水线位置的变化规律。研究表明:上水线受到的摩擦气动力与压力气动力为同一量级,在研究水线形成机理时不可忽略;在一定的来流风速范围内,摩擦气动力和压力气动力的合力可使上水线稳定在使拉索气动力发生剧烈变化的位置;在过小的风速下,水线不会稳定在拉索表面;而过大的风速会使水线远离使拉索气动力发生剧变位置。首次得到上水线摩擦气动力系数随水线位置角变化的曲线,有助于建立更准确的水线运动微分方程和更精细的拉索风雨激振理论分析模型。

The formation of upper rivulet is crucial to the occurrence of rain-wind induced vibration( RWIV) of stay cables. To understand the formation mechanism of the upper rivulet, which is still unclear, the aerodynamic characteristics of the upper rivulet were investigated using large eddy simulation(LES),which is hard to implement in wind tunnel tests. The mean pressures and skin friction on the rivulet were obtained at different rivulet position. Results showed that the friction-induced aerodynamic forces on the rivulet have the same order in quantity as the pressureinduced forces,which cannot be neglected when clarifying the mechanism of the rivulet formation. Under a certain range of wind velocity,due to the resultant of skin friction and pressure,the upper rivulet can stand on the positions where the cable aerodynamics may dramatically change. To the best of our knowledge,it is the first study to obtain the friction aerodynamic forces acting on the upper rivulet,which is very useful to developing more rational theoretical models of RWIV in the future.