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Mechanism of determination of the shedding frequency of vortices behind a cylinder at low Reynolds numbers

Published online by Cambridge University Press:  19 April 2006

Michio Nishioka  and
Hiroshi Sato
Michio Nishioka
Affiliation:
College of Engineering, University of Osaka Prefecture, Japan
Hiroshi Sato
Affiliation:
Institute of Space and Aeronautical Science, University of Tokyo, Japan
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Abstract

Two kinds of experiment were made in the wake of a cylinder at Reynolds numbers ranging between 20 and 150. One was a close look at the structure of the vortex street with a stationary cylinder at Reynolds numbers greater than 48. The other experiment was made at lower Reynolds numbers with a cylinder vibrating normal to the flow direction. In this case an artificially induced small-amplitude fluctuation grows exponentially with the rate predicted by the stability theory. Because of the similarity between the two kinds of wake, we postulate that the shedding of the vortex at low Reynolds numbers is initiated by the linear growth, namely, the fluctuation with the frequency of maximum linear growth rate develops into vortex streets. By using the measured width of the wake at the stagnation point in the wake and the result of the stability theory, we could calculate the Strouhal number for Reynolds numbers ranging from 48 to 120. The predicted Strouhal numbers agree well with the values from direct measurements.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 89 , Issue 1 , 14 November 1978 , pp. 49 - 60
Copyright
© 1978 Cambridge University Press

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