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Parametric study of the transition in the wake of oblate spheroids and flat cylinders

Published online by Cambridge University Press:  06 December 2010

MARCIN CHRUST ,
GILLES BOUCHET  and
JAN DUŠEK
MARCIN CHRUST*
Affiliation:
Institut de Mécanique des Fluides et des Solides, Université de Strasbourg/CNRS, Strasbourg 67000, France
GILLES BOUCHET
Affiliation:
Institut de Mécanique des Fluides et des Solides, Université de Strasbourg/CNRS, Strasbourg 67000, France
JAN DUŠEK
Affiliation:
Institut de Mécanique des Fluides et des Solides, Université de Strasbourg/CNRS, Strasbourg 67000, France
*
†Email address for correspondence: Marcin.Chrust@etu.unistra.fr
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Abstract

An exhaustive parametric study of the transition scenario in the wake of oblate spheroids and flat cylinders placed with their rotation axis parallel to the flow is presented. The flatness of the investigated objects is classified by the aspect ratio χ defined as χ = d/a for spheroids (with d the diameter and a the length of the polar axis) and as χ = d/h) for cylinders (with h the cylinder height). We find a significant qualitative similarity between both configurations. At large aspect ratios (χ > 2.3 for spheroids and χ ≥ 4 for cylinders), the secondary bifurcation giving rise to a periodic state without planar symmetry is subcritical with a hysteresis interval of about two Reynolds number units. For spheroids, the sphere-like scenario is recovered only at aspect ratios very close to one (χ ≥ 1 are considered), while for cylindrical bodies the same holds for χ ≤ 1.7. For intermediate aspect ratios, a domain of states with non-zero net helicity separates states typical for the sphere wake from those of an infinitely flat disk.

JFM classification

Instability: Instability Instability: Transition to turbulence Wakes/Jets: Wakes
Type
Papers
Information
Journal of Fluid Mechanics , Volume 665 , 25 December 2010 , pp. 199 - 208
Copyright
Copyright © Cambridge University Press 2010

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References

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