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Instabilities in laminar separation bubbles

Published online by Cambridge University Press:  30 August 2013

J.-C. Robinet
J.-C. Robinet*
Affiliation:
DynFluid Laboratory, Arts et Métiers ParisTech, 151 Boulevard de l’Hôpital, 75013 Paris, France
*
†Email address for correspondence: [email protected]
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Abstract

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Wall-bounded flows, in their transition from a laminar state to turbulence, pass through a set of particular stages characterized by different physical processes. Among wall-bounded flows, separated flows have a special place because their dynamics can either be noise amplifiers or oscillators. For several years Marxen and co-workers have been studying the evolution of two- and three-dimensional perturbations in the laminar part of a laminar separation bubble. In Marxen et al. (J. Fluid Mech., vol. 728, 2013, p. 58) they study vortex formation and its evolution in laminar–turbulent transition in a forced separation bubble. By the combined use of numerical and experimental methods, different mechanisms of secondary instabilities have been highlighted: elliptic instability of vortex cores and hyperbolic instability responsible for three-dimensionality in the braid region. This work shows, for the first time in laminar separation bubbles, the first nonlinear stages of transition to turbulence of such a flow. However, since this type of flow is very sensitive to various environmental stresses, several scenarios for transition to turbulence remain to be explored.

JFM classification

Boundary Layers: Boundary layer separation Instability: Nonlinear instability Vortex Flows: Vortex shedding
Type
Focus on Fluids
Information
Journal of Fluid Mechanics , Volume 732 , 10 October 2013 , pp. 1 - 4
Copyright
©2013 Cambridge University Press 

References

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