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Experimental investigation of unsteady separation in the rotor-oscillator flow

Published online by Cambridge University Press:  06 April 2018

Marc-Étienne Lamarche-Gagnon  and
Jérôme Vétel Open the ORCID record for Jérôme Vétel [Opens in a new window]
Marc-Étienne Lamarche-Gagnon
Affiliation:
Department of Mechanical Engineering, LADYF, Polytechnique Montréal, Montréal, QC H3C 3A7, Canada
Jérôme Vétel*
Affiliation:
Department of Mechanical Engineering, LADYF, Polytechnique Montréal, Montréal, QC H3C 3A7, Canada
*
†Email address for correspondence: jerome.vetel@polymtl.ca
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Abstract

Visualisations of various types of flow separation are presented in an experimental set-up that translates a rotating cylinder parallel to a wall. Particle image velocimetry is used to measure the two velocity components in a plane perpendicular to the cylinder where the flow is two-dimensional. To spatially resolve the flow close to the wall, a high-viscosity fluid is used. For a periodic translation, the fixed separation is compared to the theory of Haller (J. Fluid Mech., vol. 512, 2004, pp. 257–311), while for non-periodic translations, a method is proposed to extract the moving separation point captured by a Lagrangian saddle point, and its finite-time unstable direction (separation profiles). Intermediate cases are also presented where both types of separation, fixed and moving, are either present simultaneously or appear successively. Some results issued from numerical simulations of an impinging jet show that all the cases observed in the rotor-oscillator flow are not restricted to high-viscosity fluid motions but may also occur within any vortical flow.

JFM classification

Boundary Layers: Boundary Layers Boundary Layers: Boundary layer separation Low-Reynolds-number flows: Low-Reynolds-number flows
Type
JFM Papers
Information
Journal of Fluid Mechanics , Volume 844 , 10 June 2018 , pp. 546 - 566
Copyright
© 2018 Cambridge University Press 

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Lamarche-Gagnon et al, supplementary movie 1

Visualisation of separation for the periodic flow with H = 2D

Download Lamarche-Gagnon et al, supplementary movie 1(Video)
Video 4.1 MB

Lamarche-Gagnon et al, supplementary movie 2

Visualisation of separation for the periodic flow with H = D

Download Lamarche-Gagnon et al, supplementary movie 2(Video)
Video 1.4 MB

Lamarche-Gagnon et al, supplementary movie 3

Prediction of moving separation

Download Lamarche-Gagnon et al, supplementary movie 3(Video)
Video 344.8 KB

Lamarche-Gagnon et al, supplementary movie 4

Ejection of particles for the case of the periodic flow with a long period

Download Lamarche-Gagnon et al, supplementary movie 4(Video)
Video 12.4 MB