上游静止柱体对圆柱体结构尾激振动的影响

文章运用半隐式特征线分裂算子有限元算法对串列布置的静止上游柱体和下游圆柱的尾激振动问题进行了数值模拟研究。数值结果表明:上游柱体结构的形状、尺寸比(d/D)和折减速度(Ur)三个参数对下游圆柱体结构的动力响应、运动轨迹与涡脱落模态有着显著的影响,且与单圆柱工况相比存在明显区别;随着尺寸比的增大,上/下游柱体结构之间的互扰作用会由流致效应逐渐转变为尾流效应,使得频率特性发生变化,并会导致下游圆柱体结构的振动响应增强;当d/D=0.5和1.0时,下游圆柱体结构的运动轨迹主要为“8”字形;当d/D=1.5时,除了“8”字形外,运动轨迹还会呈现双弯刀形、“双8”字形和不规则形状。通过对流体力系数与位移时程曲线及位移PSD曲线特性进行分析,揭示了其相互作用的内在机理。另外,下游圆柱体结构的尾流场特性也会随参数的变化而变化,其涡脱落模态主要为2S、P+S和2P三种。

Effect of wake-induced vibration of the circular cylinder behind a stationary cylinder

Wake-induced vibration(WIV)of a rear two-degree-of-freedom(2-DOF)circular cylinder which is placed behind a stationary cylinder with tandem arrangement was numerically investigated by using semiimplicit characteristics-based split(CBS)finite element algorithm.Numerical results demonstrate that the in?fluence of the shape of the upstream cylinder,size ratio(d/D)and reduced velocity(Ur)on the dynamic re?sponses,X-Y trajectories,vortex shedding modes of the rear circular cylinder is significant.And there is a great difference from the single cylinder case.With the increase of the d/D,the interaction between the up?stream cylinder and the downstream one changes from the flow-induced interference to the wake one,result?ing in the change of the frequency characteristics and the intensifying dynamic response of the downstream circular cylinder.When d/D=0.5 and 1.0,the motion orbit of the rear cylinder structure is mainly the‘8’course.However,when d/D=1.5,besides the‘8’course,the double machete,figure‘dual-8’and irregular shape are observed.The mechanism of the interaction between cylinders are revealed by analysis of the time histories of fluid force coefficients and displacements as well as the power spectral density(PSD)features of the displacement on the rear circular cylinder.In addition,the upstream cylinder shape and the reduced ve?locity have a great effect on the vortex shedding mode of the rear circular cylinder.And the predominant vor?tex shedding patterns are 2S,P+S and 2P mode.