由圆柱体夹紧的倒旗的起始不稳定性

IF 3.5 2区 工程技术 Q1 ENGINEERING, MECHANICAL
Haokui Jiang, Yujia Zhao, Shunxiang Cao
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引用次数: 0

摘要

数值研究了圆柱夹持二维倒旗的水动力特性,分析了其失稳机理。对于不同直径的气缸,在该配置下有两条过渡路线,共存在6种解决方案。其中,对于小圆柱体,通过弱非线性分析和全局线性不稳定性分析判断,未变形平衡UE通过超临界干草叉分叉向变形偏转稳定SDS转变。失稳机理是工作在弹性旗前缘的“对称破缺”型SM的升力效应。对于大型圆柱体,另一种不稳定的“旋涡脱落”模式VM(与结构模式解耦)导致UE和SDS解决方案消失,取而代之的是小幅度的扑动。SM和VM分别对旗区和下游柱区扰动的增长起主要作用,可以激发多模振荡跃迁,通过适当的正交分解分析。此外,我们定义了两个临界直径Dc和DVM,将UE过渡到变形偏转的稳定或小幅度扑动,Dc和DVM都随着雷诺数的增加而减小。最后,证明了下游旋涡脱落可以诱导旗子的向上涡激振动,进一步提高了小偏转扑动过程中流体向结构传递能量的效率。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Onset instability of inverted flags clamped by a cylinder
We numerically investigate the hydrodynamic characteristics and analyze the instability mechanism of a two-dimensional inverted flag clamped by a cylinder. There are two transition routes and a total of six kinds of solutions existing under this configuration for different diameters of cylinders. Specifically, for small cylinders, the undeformed equilibrium UE transitions to deformed-deflected stable SDS through a supercritical pitchfork bifurcation, which is judged by the weakly nonlinear analysis together with the global linear instability analysis. The instability mechanism is the lifting effect of the ‘symmetry-breaking’ mode SM working at the leading edge of the elastic flag. For large cylinders, another unstable ‘vortex-shedding’ mode VM (decoupled with structure mode) causes the disappearance of the UE and SDS solutions, replaced by a small amplitude flapping. The SM and the VM mainly contribute to the growth of perturbations in flag and downstream cylinder regions respectively, which can excite multi-mode oscillating transition analyzed by proper orthogonal decomposition. Moreover, we define two critical diameters Dc and DVM dividing the transition from UE to deformed-deflected stable or small amplitude flapping, and both Dc and DVM decreases with the increase of Reynolds number. Finally, we prove downstream vortex shedding can induce upward vortex-induced vibration of the flag and further improve the efficiency of energy transfer from the fluid to the structure during small-deflection flapping.
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来源期刊
Journal of Fluids and Structures
Journal of Fluids and Structures 工程技术-工程:机械
CiteScore
6.90
自引率
8.30%
发文量
173
审稿时长
65 days
期刊介绍: The Journal of Fluids and Structures serves as a focal point and a forum for the exchange of ideas, for the many kinds of specialists and practitioners concerned with fluid–structure interactions and the dynamics of systems related thereto, in any field. One of its aims is to foster the cross–fertilization of ideas, methods and techniques in the various disciplines involved. The journal publishes papers that present original and significant contributions on all aspects of the mechanical interactions between fluids and solids, regardless of scale.
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