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Applied Mathematics and Mechanics (English Edition) ›› 2017, Vol. 38 ›› Issue (3): 439-452.doi: https://doi.org/10.1007/s10483-017-2174-8

• 论文 • 上一篇    下一篇

Instability of cylinder wake under open-loop active control

Yadong HUANG, Benmou ZHOU, Zhaolie TANG   

  1. Science and Technology on Transient Physics Laboratory, Nanjing University of Science and Technology, Nanjing 210094, China
  • 收稿日期:2016-01-27 修回日期:2016-07-01 出版日期:2017-03-01 发布日期:2017-03-01
  • 通讯作者: Benmou ZHOU, E-mail:bmzhou@mail.njust.edu.cn E-mail:bmzhou@mail.njust.edu.cn
  • 基金资助:

    Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education (No. 20133219110039)

Instability of cylinder wake under open-loop active control

Yadong HUANG, Benmou ZHOU, Zhaolie TANG   

  1. Science and Technology on Transient Physics Laboratory, Nanjing University of Science and Technology, Nanjing 210094, China
  • Received:2016-01-27 Revised:2016-07-01 Online:2017-03-01 Published:2017-03-01
  • Contact: Benmou ZHOU E-mail:bmzhou@mail.njust.edu.cn
  • Supported by:

    Project supported by the Specialized Research Fund for the Doctoral Program of Higher Education (No. 20133219110039)

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摘要：

Instability of a wake controlled by a streamwise Lorentz force is investigated through a Floquet stability analysis. The streamwise Lorentz force, which is a two-dimensional control input created by an electromagnetic actuator located on the cylinder surface, adjusts the base flow to affect the three-dimensional wake instability and achieve wake stabilization and transition delay. The instability mode at a Reynolds number Re=300 can be transformed from B to A with N=1.0, where N is an interaction number representing the strength of the Lorentz force relative to the inertial force in the fluid. The wake flow is Floquet stable when N increases to 1.3. The spanwise perturbation wavelengths are 3.926D and 0.822D in the modes A and B, respectively, where D is the cylinder diameter. In addition, the oscillating amplitudes of drag and lift are reduced with the increase in the interaction number. Particle tracing is used to explore the essential physical mechanism for mode transformation. The path lines show that suppression of flow separation hinders the fluid deformation and rotation, leading to the decrease in elliptic and hyperbolic instability regions, which is the material cause of mode transformation. All of the results indicate that wake stabilization and transition delay can be achieved under open-loop active control via the streamwise Lorentz force.

关键词: streamwise Lorentz force, global stability analysis, open-loop active control, transition delay, flow instability, wake stabilization

Abstract:

Instability of a wake controlled by a streamwise Lorentz force is investigated through a Floquet stability analysis. The streamwise Lorentz force, which is a two-dimensional control input created by an electromagnetic actuator located on the cylinder surface, adjusts the base flow to affect the three-dimensional wake instability and achieve wake stabilization and transition delay. The instability mode at a Reynolds number Re=300 can be transformed from B to A with N=1.0, where N is an interaction number representing the strength of the Lorentz force relative to the inertial force in the fluid. The wake flow is Floquet stable when N increases to 1.3. The spanwise perturbation wavelengths are 3.926D and 0.822D in the modes A and B, respectively, where D is the cylinder diameter. In addition, the oscillating amplitudes of drag and lift are reduced with the increase in the interaction number. Particle tracing is used to explore the essential physical mechanism for mode transformation. The path lines show that suppression of flow separation hinders the fluid deformation and rotation, leading to the decrease in elliptic and hyperbolic instability regions, which is the material cause of mode transformation. All of the results indicate that wake stabilization and transition delay can be achieved under open-loop active control via the streamwise Lorentz force.

Key words: streamwise Lorentz force, flow instability, global stability analysis, wake stabilization, open-loop active control, transition delay

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