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A lock-in effect in the flowover two cylinders

Published online by Cambridge University Press:  04 July 2016

F. H. Barnes,
A. J. Baxendale and
I. Grant
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Summary

Measurements are presented of the frequency of vortex shedding from two circular cylinders in a staggered arrangement. Seven different cylinders were used in turn as the upstream cylinder and the ratio of the diameter of the upstream cylinder to that of the downstream cylinder ranged from 0·00422 to 0·571. For a constant free-stream velocity changing the upstream cylinder changed the frequency of vortex shedding from the cylinder. It was found that the frequency of vortex shedding from the downstream cylinder N synchronised with that of the upstream cylinder n over a range of the latter frequency. When the frequencies were synchronised the ratio of the frequencies was given by n/N = 2. This behaviour is characteristic of a lock-in process.

Lock-in was found at each of the four upstream cylinder positions tried. However, it was only when the upstream cylinder position was such that the upstream cylinder only weakly affected the flow about the downstream cylinder that lock-in was accompanied by a decrease in the base pressure. The time-mean drag force then increased with lock-in, but by a small amount only. On the other hand the fluctuating lift force increased substantially.

Information

Type
Research Article
Information
The Aeronautical Journal , Volume 90 , Issue 894 , April 1986, pp. 128 - 138
Copyright
Copyright © Royal Aeronautical Society 1986 

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Footnotes

*

Department of Physics, University of Edinburgh, Edinburgh.

†

Department of Offshore Engineering, Heriot-Watt University, Edinburgh.

References

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