弹性圆柱在轴向来流中涡激振荡的直接数值模拟研究

发布时间：2018-01-01 17:32

本文关键词：弹性圆柱在轴向来流中涡激振荡的直接数值模拟研究　出处：《浙江大学》2015年硕士论文　论文类型：学位论文

【摘要】：圆柱涡激振荡问题广泛存在于机械、海洋、航空等工程中,由于该问题中流体和固体运动是相互耦合的,对其做数值计算是个很大的挑战。本论文使用直接力/虚拟区域法对一端固定一端自由的弹性圆柱在轴向来流中的涡激振荡问题进行了直接数值模拟,着重分析了无量纲参数包括雷诺数、无量纲剪切模量、圆柱-流体密度比对圆柱振荡运动的影响以及相关流场的涡结构、尾涡脱落过程。当限制弹性圆柱在轴向来流中做平面振动时,弹性圆柱振荡呈对称性,并且主要做拍动振动。增加雷诺数或减小密度比均可使其无量纲振荡频率(St)加大,无量纲剪切模量对振动频率的影响非常小。振幅随雷诺数和密度比的增大而增大,随无量纲剪切模量的增大而减小,其中密度比的影响最为显著。尾涡主要呈现为对称的发夹涡。当去掉平面振动中的约束后,自由端开始做转圈振动。当振荡呈现“circle”模态时,两个方向的振幅相当,合成运动为单峰振动。当振荡呈现“ellipse”模态时,自由端运动轨迹接近椭圆形,合成运动为双峰振动。与平面振动类似,振幅均会随着雷诺数和密度比的增加而增大,随无量纲剪切模量的增大而减小,振幅对密度比的变化最敏感。无量纲频率(St)随密度比的增加而变小,同时无量纲剪切模量对无量纲频率的影响和模态相关。雷诺数和无量纲剪切模量对振动模态的影响相互制约。“circle”模态尾涡为连续脱落的旋转发夹涡。
[Abstract]:The problem of cylindrical vortex-induced oscillations is widely used in mechanical, marine, aviation and other engineering, because of the fluid and solid motion is coupled with each other in this problem. The direct force / virtual domain method is used to simulate the vortex-induced oscillations of an elastic cylinder with one fixed end and one free end in axial flow. The effects of dimensionless parameters such as Reynolds number, dimensionless shear modulus, the ratio of cylindrical to fluid density on the oscillatory motion of the cylinder and the vortex structure of the related flow field are analyzed emphatically. Wake vortex shedding. When the elastic cylinder is confined to the plane vibration in the axial flow, the elastic cylinder oscillates symmetrically. The frequency of dimensionless oscillation can be increased by increasing Reynolds number or decreasing density ratio. The effect of dimensionless shear modulus on vibration frequency is very small. The amplitude increases with the increase of Reynolds number and density ratio, and decreases with the increase of dimensionless shear modulus. The effect of density ratio is the most obvious. The wake vortex is mainly a symmetrical hairpin vortex. When the constraint in the plane vibration is removed, the free end begins to make the rotation vibration. When the oscillation presents the "circle" mode. The amplitude of the two directions is equal, the synthetic motion is a single peak vibration, when the oscillation presents "ellipse" mode, the free end motion trajectory is close to the ellipse, and the synthetic motion is a bimodal vibration, which is similar to the plane vibration. The amplitude increases with the increase of Reynolds number and density ratio, and decreases with the increase of dimensionless shear modulus. The amplitude is most sensitive to the change of density ratio, and the dimensionless frequency Stg becomes smaller with the increase of density ratio. At the same time, the influence of dimensionless shear modulus on the dimensionless frequency is related to the mode. The influence of Reynolds number and dimensionless shear modulus on the vibration mode is restricted. "circle" The modal wake is a rotating hairpin vortex with continuous shedding.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：O32

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