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Effect of Mach number on the structure of turbulent spots

Published online by Cambridge University Press:  05 October 2006

L. KRISHNAN  and
N. D. SANDHAM
L. KRISHNAN
Affiliation:
Aeronautics and Astronautics, School of Engineering Sciences, University of Southampton, SO17 1BJ, UK
N. D. SANDHAM
Affiliation:
Aeronautics and Astronautics, School of Engineering Sciences, University of Southampton, SO17 1BJ, UK
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Abstract

Direct numerical simulations have been performed to study the dynamics of isolated turbulent spots in compressible isothermal-wall boundary layers. Results of a bypass transition scenario at Mach 2, 4 and 6 are presented. At all Mach numbers the evolved spots have a leading-edge overhang, followed by a turbulent core and a calmed region at the rear interface. The spots have an upstream-pointing arrowhead shape when visualized by near-wall slices, but a downstream-pointing arrowhead in slices away from the wall. The lateral spreading of the spot decreases substantially with the Mach number, consistent with a growth mechanism based on the instability of lateral shear layers. Evidence for a supersonic (Mack) mode substructure is found in the Mach 6 case, where coherent spanwise structures are observed under the spot overhang region.

Type
Papers
Information
Journal of Fluid Mechanics , Volume 566 , 10 November 2006 , pp. 225 - 234
Copyright
© 2006 Cambridge University Press

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