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The structure of a turbulent spot in Blasius flow

Published online by Cambridge University Press:  20 April 2006

J. Barrow ,
F. H. Barnes ,
M. A. S. Ross  and
S. T. Hayes
J. Barrow
Affiliation:
Physics Department, University of Edinburgh
F. H. Barnes
Affiliation:
Physics Department, University of Edinburgh
M. A. S. Ross
Affiliation:
Physics Department, University of Edinburgh
S. T. Hayes
Affiliation:
Edinburgh Regional Computer Centre
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Abstract

Turbulent spots formed artificially in a Blasius boundary layer have been investigated over a finite width extending across the plane of symmetry of the spots. Hot wires were used to measure the local mean and fluctuating parts of the downstream and spanwise velocity components, and the third component was computed. The results are presented in contour diagrams, and are compared with previous published work.

The values of energy thickness in the spots are computed from the contours of downstream velocity. The spots are found to consist of an upper part containing most of the turbulence, moving over a lower layer whose contribution to the energy thickness is small. When, near the rear of the spot, the energy thickness decreases to the value in Blasius flow, the two parts recombine, and the flow slowly regains the Blasius velocity profile.

The spots grow by entrainment of laminar fluid, and the physical principles governing this process are discussed.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 149 , December 1984 , pp. 319 - 337
Copyright
© 1984 Cambridge University Press

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