Applied Mathematics and Mechanics (English Edition) ›› 2016, Vol. 37 ›› Issue (8): 999-1012.doi: https://doi.org/10.1007/s10483-016-2113-8

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Global instability of Stokes layer for whole wave numbers

Wei KONG, Jisheng LUO   

  1. Department of Mechanics, Tianjin University, Tianjin 300072, China
  • 收稿日期:2015-05-18 修回日期:2016-03-23 出版日期:2016-08-01 发布日期:2016-08-01
  • 通讯作者: Jisheng LUO E-mail:jsluo@tju.edu.cn
  • 基金资助:

    Project supported by the National Natural Science Foundation of China (No. 11202147) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20120032120007)

Global instability of Stokes layer for whole wave numbers

Wei KONG, Jisheng LUO   

  1. Department of Mechanics, Tianjin University, Tianjin 300072, China
  • Received:2015-05-18 Revised:2016-03-23 Online:2016-08-01 Published:2016-08-01
  • Contact: Jisheng LUO E-mail:jsluo@tju.edu.cn
  • Supported by:

    Project supported by the National Natural Science Foundation of China (No. 11202147) and the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20120032120007)

摘要:

The study on the global instability of a Stokes layer, which is a typical unsteady flow, is usually a paradigm for understanding the instability and transition of unsteady flows. Previous studies suggest that the neutral curve of the global instability obtained by the Floquet theory is only mapped out in a limited range of wave numbers (0.2≤α≤0.5). In this paper, the global instability is investigated with numerical simulations for all wave numbers. It is revealed that the peak of the disturbances displays irregularity rather than the periodic evolution while the wave number is beyond the above range. A "neutral point" is redefined, and a neutral curve of the global instability is presented for the whole wave numbers with this new definition. This work provides a deeper understanding of the global instability of unsteady flows.

关键词: Floquet theory, instantaneous instability, Stokes layer, neutral curve

Abstract:

The study on the global instability of a Stokes layer, which is a typical unsteady flow, is usually a paradigm for understanding the instability and transition of unsteady flows. Previous studies suggest that the neutral curve of the global instability obtained by the Floquet theory is only mapped out in a limited range of wave numbers (0.2≤α≤0.5). In this paper, the global instability is investigated with numerical simulations for all wave numbers. It is revealed that the peak of the disturbances displays irregularity rather than the periodic evolution while the wave number is beyond the above range. A "neutral point" is redefined, and a neutral curve of the global instability is presented for the whole wave numbers with this new definition. This work provides a deeper understanding of the global instability of unsteady flows.

Key words: neutral curve, Floquet theory, instantaneous instability, Stokes layer

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