不同剪切率来流作用下柔性圆柱涡激振动数值模拟  

NUMERICAL SIMULATION OF VORTEX-INDUCED VIBRATION OF A FLEXIBLE CYLINDER EXPOSED TO SHEAR FLOW AT DIFFERENT SHEAR RATES

作　　者：及春宁[1] 花阳 许栋[1] 邢国源 陈威霖[1] Ji Chunning;Hua Yang;Xu Dong;Xing Guoyuan;Chen Weilin(State Key Laboratory of Hydraulic Engineering Simulation and Safety,Tianjin University,Tianjin 300072,China)

机构地区：[1]天津大学水利仿真与安全国家重点实验室,天津300072

出　　处：《力学学报》2018年第1期21-31,共11页Chinese Journal of Theoretical and Applied Mechanics

基　　金：国家自然科学基金(51579175;51779172);天津市应用基础与前沿技术研究计划(12JCQNJC02600);NSFC-广东联合基金(第二期)超级计算科学应用研究专项(U1501501);国家超级计算广州中心支持项目

摘　　要：采用浸入边界法对细长柔性圆柱在线性剪切流条件下的涡激振动进行三维数值模拟.细长柔性圆柱振动采用三维索模型模拟,其两端铰接,质量比为6,长细比为50,无量纲顶张力为496.来流为线性剪切流,剪切率从0到0.024变化,最大雷诺数为250.研究发现:剪切流作用下柔性立管横流向振动表现为驻波模式,而顺流向振动表现为行波与驻波混合模式.随着剪切率增大,振动频谱呈现多频响应,振动能量逐渐向低频转移.阻力系数平均值随着展向变化,脉动阻力系数和升力系数的均方根值均表现为"双峰"模式.流固能量传递系数沿立管轴向的分布表明,振动激励区集中于高流速区,而振动阻尼区多位于低流速区.剪切率较小时,圆柱的泻涡为平行交叉模式;剪切率较大时,圆柱的泻涡为倾斜泻涡模式,且由于泻涡频率沿立管轴向变化,尾流发生涡裂现象,形成泻涡频率不同的胞格结构.In this paper,the immersed boundary method was used to simulate the vortex-induced vibration of a slender flexible cylinder exposed to linear shear flows.The vibration of the cylinder was simulated by using a three-dimensional cable model pinned at both ends.The cylinder has a mass ratio of 6 and an aspect ratio of 50.The normalized top tension is 496.The incoming flow has different linear velocity profiles with the shear rates ranging from 0 to 0.024.The maximum Reynold number is 250.It was found that the transverse vibration shows a standing wave pattern while the streamwise vibration shows a combined traveling-standing wave pattern.With the increase of the shear rate,the distribution of power spectrum density(PSD)of vibration responses shows a multi-frequency mode,and the vibration energy shifts to low frequency bands.The mean drag coefficient varies in the spanwise direction while the root-meansquare(RMS)values of fluctuating drag and lift coefficients show a two-peak pattern.The distribution of the fluid-solid energy transferring coefficient indicates that the vibration-exciting region coincides with the high-velocity region while the vibration-damping region matches the low-velocity region.For the cases with low shear rates,the vortex-shedding behind the cylinder shows the interwoven pattern.However,for the cases with large shear rates,the vortex-shedding displays the oblique pattern.Due to the spanwise variation of the vortex-shedding frequency,the vortex-splitting occurs in the near-wake,leading to the vortex cells with different vortex-shedding frequencies.

关 键 词：柔性圆柱 涡激振动 剪切流 流固能量传递 涡裂 

分 类 号：P751[交通运输工程—港口、海岸及近海工程] TB531[天文地球—海洋科学]