竖立圆柱涡激振动尖端效应的数值模拟研究

Numerical simulation on tip effect of vortex-induced vibration around an upright cylinder

有限长悬臂圆柱结构在风载荷作用下可能会发生普通涡激振动。同时,在超过锁振范围的高风速下也可能发生涡激振动现象,这种涡激振动现象产生的机理尚不明确。针对普通涡激振动现象和高风速下涡激振动现象建立双向流固耦合数值模拟方法进行分析。结果表明,通过数值模拟方法可以较好的呈现出圆柱在风载荷作用下的振动特性以及流场在圆柱展向上的三维流动特性。通过对圆柱顶部面中心点的位移时程曲线以及耦合面上的升力时程曲线进行功率谱密度分析,得到与文献实验结果较为吻合的普通涡激振动频率响应。根据圆柱运动的横向振动特性以及三维流动特性,发现当圆柱处于高风速下在其尖端处存在接近结构固有频率的涡泄频率,揭示在高风速下发生涡激振动的机理。

The vortex-induced vibration of the finite-length cantilever cylindrical structure may occur under the wind load.At the same time,vortex-induced vibration may also occur at high wind speeds beyond the range of the lock vibration.The mechanism of this vortex-induced vibration phenomenon is not yet clear.Aiming at the common vortex-induced vibration phenomenon and the vortex-induced vibration phenomenon under high wind speed,a two-way fluid-structure interaction numerical simulation method was established for analysis.The results show that the numerical simulation method can better show the vibration characteristics of the cylinder under the wind load and the three-dimensional characteristics of the fluid flow in the cylinder span.By performing the power spectral density analysis on the displacement time history curve of the center point of the cylinder top surface and the lift time history curve on the coupling surface,a common vortex-induced vibration frequency response that is in good agreement with the experimental results in the literature was obtained.According to the lateral vibration characteristics and three-dimensional flow characteristics of the cylinder motion,it was found that when the cylinder is at high wind speed,there is a vortex frequency close to the natural frequency of the structure at the tip of the cylinder,which reveals the mechanism of vortex-induced vibration at high wind speed.