两端铰接的细长柔性圆柱体涡激振动响应特性数值研究

目前细长柔性圆柱体涡激振动响应的研究方法主要包括实验方法、计算流体动力学方法以及半经验模型方法. 鉴于实验方法研究成本较高、计算流体动力学方法计算时间较长,本文基于尾流振子模型对线性剪切来流下两端铰接的细长柔性圆柱体涡激振动响应特性进行了半经验模型方法研究. 先建立了柔性圆柱体结构振子以及尾流振子之间的耦合模型,紧接着基于二阶精度中心差分格式对耦合模型先离散后迭代进行求解. 对不同剪切参数下柔性圆柱体涡激振动响应的振动波长、振动频率、振动位移以及响应频率随时间的变化特性等参数进行了分析. 分析结果表明:圆柱体的涡激振动响应由驻波和行波混合组成. 当无量纲弯曲刚度较小时,在圆柱体两端附近,驻波占主导;而在圆柱体中间段附近,行波占主导. 当无量纲弯曲刚度较大时,在圆柱体整个长度区间上均为驻波占主导. 随着剪切参数的增大,振动位移以及振动波长均逐渐减小,而振动频率和频率带宽均逐渐增大. 

NUMERICAL STUDY OF RESPONSE PERFORMANCE OF VORTEX-INDUCED VIBRATION ON A FLEXIBLE CYLINDER WITH PINNED-PINNED BOUNDARY CONDITION

Nowadays, the study methods of VIV on long flexible cylinders contain experimental method, computational fluid dynamic method and semi-empirical method. Due to the expensive cost of experimental method and the long computational time of computational fluid dynamics method, a semi-empirical method study based on a wake oscillator model has been conducted to determine the response performance of vortex-induced vibration (VIV) on a long flexible cylinder with pinned-pinned ends under linearly sheared currents. The coupled model of the structural oscillator of a flexible cylinder and wake oscillator is established, and then the model is discretized and solved based on a standard central finite difference method of the second order. The VIV response characteristics including vibration wavelength, vibration frequency, vibration displacement and frequency varied with time at different shear parameters are compared. The numerical results show that the VIV response is composed of standing wave response and travelling wave response. For a cylinder with small dimensionless bending stiffness, the standing wave response is dominated near the ends while the travelling wave response is dominated near the middle part. However, for a cylinder with large dimensionless bending stiffness, the standing wave response is dominated along the entire cylinder span. As the sheared current increases, the vibration wavelength and displacement decrease, however, the vibration frequency and frequency width increase.