Convective instability in inhomogeneous media: Impulse response in the subcritical cylinder wake

We study experimentally the impulse response of a cylinder wake below the critical Reynolds number of the Bénard–von Kármán instability. In this subcritical regime, a localized inhomogeneous region of convective instability exists which causes initial perturbations to be transiently amplified. The a...

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Bibliographic Details
Published in:Physics of fluids (1994) 2011-01, Vol.23 (1)
Main Authors: MARAIS, C, GODOY-DIANA, R, BARKLEY, D, WESFREID, J. E
Format: Article
Language:English
Subjects:
Buoyancy-driven instability
Exact sciences and technology
Fluid dynamics
Fundamental areas of phenomenology (including applications)
Hydrodynamic stability
Physics
Rotational flow and vorticity
Separated flows
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Summary:We study experimentally the impulse response of a cylinder wake below the critical Reynolds number of the Bénard–von Kármán instability. In this subcritical regime, a localized inhomogeneous region of convective instability exists which causes initial perturbations to be transiently amplified. The aim of this work is to quantify the evolution resulting from this convective instability using two-dimensional particle image velocimetry in a hydrodynamic tunnel experiment. The velocity fields allow us to describe the evolution of wave packets in terms of two control parameters: the Reynolds number and the magnitude of the imposed perturbation. The temporal evolution of energy exhibits a transient algebraic growth at short times followed by an exponential decay.
ISSN:1070-6631
1089-7666
DOI:10.1063/1.3531724