围绕半球形圆柱体的涡旋振荡机制

IF 3.6 2区 工程技术 Q1 MECHANICS
Zhou-Yang Wang, Bao-Feng Ma
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引用次数: 0

摘要

以往的研究表明,在不同的攻角下,半球形气缸体周围会出现低频涡旋振荡,但其基本机制仍不清楚。在本研究中,我们利用数值模拟和全局线性稳定性分析研究了涡旋振荡的起源。通过数值模拟再现了涡旋振荡,并通过动态模式分解(DMD)计算了振荡模式。我们通过选择性频率阻尼法获得了基流,基流在主体上方呈现出一对稳定的背风涡旋。四种不稳定模态采用改进的阿诺德迭代法计算。发现斯特劳哈尔数为 0.105 的非对称模态负责涡旋对的交替振荡,斯特劳哈尔数为 0.220 的模态对应于同相涡旋振荡。它们的频率与 DMD 的模式十分吻合。另外两个频率较高的不稳定模式,一个是反对称模式,一个是对称模式,是上述两个模式的谐波频率。这项研究最终验证了半球形圆柱体上的涡旋振荡源于全局流动不稳定性。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Mechanism of vortex oscillation around a hemisphere–cylinder body
Previous studies have shown that low-frequency vortex oscillations occur around a hemisphere–cylinder body at different angles of attack, but the underlying mechanism is still unclear. In this study, we examine the origin of the vortex oscillation using numerical simulations and global linear stability analysis. The vortex oscillation is reproduced using numerical simulations, and the oscillatory modes are computed through dynamic mode decomposition (DMD). We obtain the base flow through a selective frequency damping method, which exhibits a pair of steady leeward vortices over the body. The four unstable modes are computed using a modified Arnoldi iteration. The antisymmetric mode with a Strouhal number of 0.105 is discovered to be responsible for the alternate oscillation of the vortex pair, and the mode with a Strouhal number of 0.220 corresponds to the in-phase vortex oscillation. Their frequencies have good agreement with the modes of DMD. The other two unstable modes with higher frequencies, one antisymmetric and one symmetric, are harmonic frequencies of the above two modes. The study conclusively verifies that the vortex oscillation over a hemisphere–cylinder body originates from a global flow instability.
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来源期刊
CiteScore
6.50
自引率
27.00%
发文量
945
审稿时长
5.1 months
期刊介绍: Journal of Fluid Mechanics is the leading international journal in the field and is essential reading for all those concerned with developments in fluid mechanics. It publishes authoritative articles covering theoretical, computational and experimental investigations of all aspects of the mechanics of fluids. Each issue contains papers on both the fundamental aspects of fluid mechanics, and their applications to other fields such as aeronautics, astrophysics, biology, chemical and mechanical engineering, hydraulics, meteorology, oceanography, geology, acoustics and combustion.
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