低雷诺数下弹性圆柱体涡激振动及影响参数分析

Analysis of vortex-induced vibration of an elastic cylinder and influence parameters at low Reynolds number

利用Fluent软件数值求解不可压缩粘性流体的N-S方程,研究均匀来流Re=200时弹性圆柱体的涡激振动。圆柱体运动简化为质量-弹簧-阻尼系统,将Newmark-β方法代码写入用户自定义函数(UDF)求解运动方程,柱体与流体间的非线性耦合作用通过动网格技术实现。详细分析了涡激力系数、柱体位移特征值和尾流涡结构随频率比的变化关系,获得"相位开关"、"拍"等现象。考虑流向振动对横向振动影响时,圆柱体最大横向振幅为0.65倍直径。当固定频率比,而质量比或折合阻尼增大时,圆柱体流向与横向振动均呈非线性衰减趋势,但增大质量比对流向平均位移的偏离起到更好的控制效果。

Through numerical simulation based on the Fluent, the Vortex-induced vibration of an elastic cylinder in uniform flow with Re= 200 was obtained by solving the incompressible viscous fluid N-S equations. The cylinder motion was modeled by a mass-spring-damper system, and the motion equation of the cylinder was solved by Newmark-β method which was manually written into the User Defined Functions of Fluent. To realize the nonlinear coupling between cylinder and flow, the dynamic mesh technique was utilized. The dependences of the characteristic value of both the vortex induced force coefficient and the cylinder＇s displacement, the wake structure on the frequency ratio were analyzed in detail, respectively. The results including ＂phase switch＂, ＂beat＂ phenomena were obtained successfully. When the influence of streamwise vibration on transverse vibration is taken into consideration, the maximum amplitude of transverse vibration is 0.65 times the diameter. Either of the increment of mass ratio and reduced damping will nonlinearly reduce both the streamwise and transverse vibration as long as the frequency ratio remain unchanged; however, the increment of the mass ratio can control the average displacement deviation of streamwise vibration more effectively.