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Characteristics of Ekman boundary layer instabilities

Published online by Cambridge University Press:  29 March 2006

D. R. Caldwell  and
C. W. Van Atta
D. R. Caldwell
Affiliation:
Department of Oceanography, Oregon State University
C. W. Van Atta
Affiliation:
Scripps Institution of Oceanography, University of California at San Diego
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Abstract

In a laboratory study, the class of instabilities of the laminar Ekman layer called type II (or class A) are found to have the spectral characteristics of narrow-band noise (Q ∼ 5). The unperturbed laminar profile resembles very closely the ideal Ekman solution. The frequency of the spectral peak varies with the Reynolds number as predicted theoretically by Lilly (1966), but the measured frequencies are only 60% of the predicted value. The critical Reynolds number for this instability is found to be 56·7, in good agreement with Lilly's analysis. The measured boundary layer profile of the magnitude of the spectral peak has the behaviour predicted by Lilly. A sudden onset of turbulence is found at a Reynolds number of 148.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 44 , Issue 1 , 21 October 1970 , pp. 79 - 95
Copyright
© 1970 Cambridge University Press

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References

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