薄平板断面气动自激力振幅效应数值模拟

Numerical Simulation of Amplitude Effects on Aerodynamic Self-excited Forces of Thin Plate Section

为研究振幅对桥梁主梁断面气动自激力的影响,以薄平板断面为研究对象,采用计算流体动力学(Computational Fluid Dynamics,CFD)方法进行气动自激力振幅效应研究.首先采用强迫振动数值模拟方法,研究了不同振幅下薄平板断面颤振导数与气动力迟滞相位,分析了薄平板断面气动力的频谱特性;然后采用自由振动数值模拟方法,研究了薄平板断面的颤振响应演变规律.薄平板断面强迫振动数值模拟结果表明:扭转振幅对薄平板断面颤振导数影响较大,在高折算风速下,颤振导数A*2随着振幅的增大由负转正,竖向振幅对薄平板断面颤振导数影响相对较小;扭转振幅的增大引起薄平板断面气动力迟滞相位正弦值发生了较大变化;当扭转振幅大于8°时,薄平板断面气动力存在较为明显的高次谐波分量,主要为三阶与五阶分量,竖向振幅引起的薄平板断面气动力高阶分量不明显.薄平板断面自由振动数值模拟结果表明:薄平板断面在颤振发散过程中,其瞬时频率、瞬时阻尼比与竖向扭转位移相位差均随振幅变化.

In order to study the amplitude effects on self-excited aerodynamic forces of the bridge main deck section,a thin plate section was taken as the research object,and the amplitude effects of aerodynamic self-excited forces were studied by using computational fluid dynamics(CFD)method.First,the numerical simulation method of forced vibration was used to investigate the flutter derivatives and aerodynamic hysteresis phases of the thin plate sec-tion under different amplitudes.The aerodynamic spectrum characteristics of the thin plate section were analyzed.Then,the numerical simulation method of free vibration was used to study the flutter response evolution characteristics of the thin plate section.The numerical simulation results of forced vibration for the thin plate section show that the torsional amplitude has significant effects on the flutter derivatives of the thin plate section.At high reduced wind speed,the flutter derivative A2*changes from negative to positive as the amplitude increases.The effect of vertical am-plitude on the flutter derivatives of the thin plate section is relatively small.As the torsional amplitude increases,the sinusoidal value of aerodynamic hysteresis phase of the thin plate section changes significantly.When the torsional amplitude is larger than eight degrees,there are obvious high-order harmonic components in the aerodynamic forces of the thin plate section,mainly for the third and fifth order components.The high-order components of aerodynamic forces of the thin plate section caused by the vertical amplitude are not obvious.The numerical simulation results of the free vibration of the thin plate section show that the instantaneous frequency,damping ratio and the phase difference between the vertical displacement and torsional displacement change with the vibration amplitude during the process of flutter divergence.