Vortex-induced vibration of a circular cylinder with two-degree-of-freedom and low mass ratio is investigated numerically with Reynolds-averaged Navier-Stokes (RANS) equations.The mass ratio is 2.6,and natural frequency ratio is 1.The Reynolds number is in the range of 7300 to 55000,and corresponding reduced velocity is from 2 to 15,which has covered the entire "lock-in" range.Different amplitude response branches are obtained,and vibration characteristics for each branch are analyzed and agree well with the experiment.In addition to typical vortex shedding modes for each branch,the transition of 2T and 2P is captured in the lower branches.With the change of the reduced velocity,the vibration trajectory appears various forms:moving towards upstream or downstream,clockwise or counterclockwise.In the extremely upper branches,the vibration trajectory changes from "8"-like shape to the "moon"-like shape.%论文采用RANS方法对低质量比弹性支撑圆柱体的双自由度涡激振动进行了数值模拟,圆柱体的质量比为2.6,固有频率比为1,雷诺数范围为7300～55000,相应的约化速度范围2～15,包括了经典试验中出现的整个锁定范围.文中通过数值模拟得到了不同的响应分支,重点分析了各响应分支的振动特性,与相应试验的结果吻合较好;捕捉到对应于各分支的不同典型尾涡模型,同时还发现了2T到2P的过度态;伴随约化速度的改变,振动轨迹也相应地呈现出顺时针、逆时针以及偏向来流的上游或下游方向等多种不同的形式,在超上端分支范围内,振动轨迹由“8”字形逐渐向“新月”形转变.
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