低质量比圆形四立柱涡激运动特性研究

Vortex-induced motion characteristics of four circular columns with a low mass ratio

采用有限体积法对圆形四立柱涡激运动进行数值模拟。圆形四立柱涡激运动系统简化为两自由度的质量-弹簧-阻尼模型,引入雷诺平均应力模型求解不可压缩粘性Navier-Stokes方程,并结合SST k-w湍流模型对低质量比弹性支撑的圆形四立柱涡激运动进行模拟。将四阶Runge-Kutta代码嵌入用户自定义函数UDF（User Defined Function）中求解四立柱的动力响应,采用动网格技术来实现立柱和流场之间的耦合。研究发现,圆形四立柱涡激运动流向和横向振幅随着折合速度的增大而先增大后减小,并出现幅值跳跃现象,跳跃点在折合速度9.0处。横向振幅最大值出现在折合速度为8.0时,大小为1.99D,远大于流向振幅最大值0.26D。圆形四立柱流向运动平衡位置随折合速度增大并非一直增大,在折合速度9.0时突然下降随后增大。圆形四立柱涡激运动出现了明显的频率锁定现象,锁定区间为5.0～8.0。当系统走过锁定系统后,流向幅值和流向幅值迅速减小。最后对不同折合速度下圆形四立柱运动轨迹和尾涡脱落模式进行讨论分析。

Here,the finite volume method was used to simulate vortex-induced motion of four circular columns.The vortex-induced motion system of four circular columns was simplified into a spring-mass-damping model. Reynoldsaveraged Navier-Stokes solver was combined with SST（ shear-stress transport） k-ω turbulence model for solving NavierStokes equation to simulate the vortex-induced motion of four circular columns with a low mass ratio. Fourth order RungeKutta method was manually written into the user defined functions to get the dynamic response of four circular columns,and then the dynamic mesh technology was adopted to realize the coupled fluid-structure interaction. It was shown that the amplitudes of the four circular columns firstly increase and then decrease with increase in the reduced velocity,＇jump＇phenomenon is observed in the amplitude curve at the reduced velocity of 9. 0; the transverse maximum amplitude appears at the reduced velocity of 8. 0,its value is 1. 99 D,much larger than the stream-wise maximum amplitude 0. 26D; the inline balance positions of four columns do not always increase with increase in the reduced velocity,it suddenly decreases at the reduced velocity of 9. 0 and then increase; the frequency lock-in phenomenon occurs in four circular columns vortex-induced motion,the lock-in region is in the range of the reduced velocity of 5. 0 ～ 8. 0; when the vortex-induced motion system passes the lock-in region,the stream-wise amplitude and the transverse one suddenly decrease; finally,the trajectory and tail vortex shedding pattern of four circular columns at different velocities are discussed.