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The evolution of a subharmonic mode in a vortex street

Published online by Cambridge University Press:  21 June 2005

G. J. SHEARD
Affiliation:
Fluids Laboratory for Aeronautical and Industrial Research (FLAIR), Department of Mechanical Engineering, Monash University, Melbourne, Victoria 3800, Australia
M. C. THOMPSON
Affiliation:
Fluids Laboratory for Aeronautical and Industrial Research (FLAIR), Department of Mechanical Engineering, Monash University, Melbourne, Victoria 3800, Australia
K. HOURIGAN
Affiliation:
Fluids Laboratory for Aeronautical and Industrial Research (FLAIR), Department of Mechanical Engineering, Monash University, Melbourne, Victoria 3800, Australia
T. LEWEKE
Affiliation:
Institut de Recherche sur les Phénomènes Hors Équilibre (IRPHÉ), UMR 6594 CNRS/Universités Aix-Marseille I & II, 12 avenue Général Leclerc, F-13003 Marseille, France

Abstract

The development of a subharmonic three-dimensional instability mode in a vortex street is investigated both numerically and experimentally. The flow past a ring is considered as a test case, as a previous stability analysis has predicted that for a range of aspect ratios, the first-occurring instability of the vortex street is subharmonic. For the flow past a circular cylinder, the development of three-dimensional flow in the vortex street is known to lead to turbulent flow through the development of spatio-temporal chaos, whereas subharmonic instabilities have been shown to cause a route to chaos through the development of a period-doubling cascade. The three-dimensional vortex street in the flow past a ring is analysed to determine if a subharmonic instability can alter the route to turbulence for a vortex street.

A linear stability analysis and non-axisymmetric computations are employed to compute the flow past a ring with an aspect ratio ${\sc ar}\,{=}\,5$, and comparisons with experimental dye visualizations are included to verify the existence of a subharmonic mode in the wake. Computations at higher Reynolds numbers confirm that the subharmonic instability does not initiate a period-doubling cascade in the wake.

Type
Papers
Copyright
© 2005 Cambridge University Press

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