宽高比5∶1矩形断面涡激振动锁定区间内涡激力展向相关性分析

Spanwise correlation of aerodynamic forces in the lock-in region of VIV for 5∶1 rectangular cylinder

涡激力展向相关性是准确预测三维柔性结构涡激振动振幅的重要因素。以宽高比5∶1矩形断面为例,通过气动力展向相关函数理论建模和节段模型弹性悬挂测振、测压风洞试验,研究了涡激振动锁定区间内实测气动力展向相关性变化规律。研究结果表明:在涡激振动锁定区间内,实测气动力由完全相关的自激力和不完全相关的随机气动力组成,展向相关性可以用指数加常数型函数描述,指数项系数为随机气动力占实测气动力的能量比,指数项系数和常数之和等于1;实测气动升力均方根在涡振起振阶段最大,随着风速增大反而减小,随机气动力均方根基本保持不变,由此导致实测气动力展向相关性表现为起振阶段最强,随着风速增加而减弱。

The spanwise correlation of vortex-induced forces(VIFs)is necessary to accurately predict vortex-induced vibration(VIV)amplitude of three-dimensional flexible structures.In this paper,the properties of aerodynamic spanwise correlation in the lock-in region are studied via theoretic modelling of aerodynamic spanwise correlation function and wind tunnel tests of VIV for the 5︰1 rectangular sectional model.The results show that in the vortex interval,the measured aerodynamic force consists of fully cor⁃related self-excited force and incompletely correlated random aerodynamic force.The spanwise correlation can be described by ex⁃ponential function and a constant,the exponential coefficient denotes the energy ratio of random aerodynamic force to measured aerodynamic force,and the sum of the exponential coefficient and the constant is equal to 1.The root mean square of measured aerodynamic lift is tend to be the stronger in the onset stage of VIV,but decreases with the increase of wind speed.The root mean square of random aerodynamic force seem to be identical.Therefore,the spanwise correlation of measured aerodynamic force in the onset stage is tend to the stronger than that in the following stage.