高雷诺数下串列圆柱尾流致涡激振动的机理研究

Mechanism of wake-induced vortex vibration of two tandem circular cylinders at a high Reynolds number

多圆柱之间的气动干扰常导致结构发生尾流激振。为进一步澄清双圆柱之间的气动干扰机理,采用大涡模拟(LES)方法,在高雷诺数下(Re=1.4×105)研究了串列双圆柱(圆心间距为1.5~4倍直径)的表面风压分布、气动力系数和Strouhal数等气动性能与流场流态之间的内在关系,研究了上、下游圆柱气动力之间的相关性,从平均和瞬态流场角度讨论了气动干扰效应的流场作用机制,建立了下游圆柱的激励力模型并对尾流致涡激振动进行了算例分析。研究结果表明:数值模拟得到的气动性能和流场流态与试验结果吻合较好,说明在高雷诺数下大涡模拟方法能准确模拟双圆柱气动干扰现象;随着间距的增大,串列圆柱依次呈现单一钝体、剪切层再附和双涡脱等三种干扰流态;上、下游圆柱气动力之间的相关性会随着流态的不同出现较大波动,双涡脱流态时的升力相关性最强;单一钝体流态时,两个圆柱间隙中的回流会导致下游圆柱受到负阻力的作用;双涡脱流态时,下游圆柱的脉动升力远大于其他两种流态,也明显大于单圆柱,因而下游圆柱发生尾流致涡激振动的可能性最大。

Aerodynamic interference between multiple circular cylinders often results in wake-induced vibrations.To clarify the mechanism of aerodynamic interference between two tandem circular cylinders,large eddy simulation(LES)is used to investigate the aerodynamic and flow field characteristics of the cylinders at a high Reynolds number of 1.4×10 5.Wind pressure distributions,aerodynamic coefficients,and Strouhal numbers are obtained on the two cylinders which have a center-to-center spacing of 1.5~4 times of the diameter.Flow field mechanism of the aerodynamic interference is discussed from the aspect of the instantaneous and time-averaged flow field.The correlation of aerodynamic forces between the upstream and downstream cylinder is studied as well.An incentive force model of the downstream cylinder is established and the wake-induce vortex vibration is analyzed.The results of the present numerical simulation are in good agreement with the experimental results in the literature,which indicates that the large eddy simulation method can accurately simulate the flow around two circular cylinders at the high Reynolds number.With the increase of the space between the two cylinders,the flow pattern changes from single bluff body regime,shear layer reattachment regime,and co-shedding regime.The correlation coefficients of aerodynamic forces between the upstream cylinder and the downstream one fluctuate with the flow pattern,which reaches the peak value in the co-shedding regime.For the single bluff body regime,there exists a strong recirculation region in the gap of the two cylinders,which is responsible for the negative drag exerted on the downstream cylinder.For the co-shedding regime,the fluctuating lift of the downstream cylinder is much larger than those of two other regimes and that of a single circular cylinder.Furthermore,the amplitude of the possible wake-induced vortex vibration in the co-shedding regime is larger than those of the other two regimes.