Journal of Fluid Mechanics

Papers

Lagrangian and spectral analysis of the forced flow past a circular cylinder using pulsed tangential jets

T. Jardina1 and Y. Burya1 c1

a1 Université de Toulouse, ISAE, 31055 Toulouse, France

Abstract

We numerically investigate the influence of pulsed tangential jets on the flow past a circular cylinder. To this end a spectral-Lagrangian dual approach is used on the basis of time-series data. The analysis reveals that the flow response to unsteady forcing is driven by strong interactions between shear layers and pulsed jets. The latter preferentially lead to either the lock-on regime or the quasi-steady vortex feeding regime whether the excitation frequency is of the order of, or significantly greater than, the frequency of the natural instability. The intensity of the wake vortices is mainly influenced by the momentum coefficient through the introduction of opposite-sign vorticity in the shear layers. This feature is emphasized using a modal-based time reconstruction, i.e. by reconstructing the flow field upon a specific harmonic spectrum associated with a characteristic time scale. The quasi-steady regime exhibits small-scale counter-rotating vortices that circumscribe the separated region. In the lock-on regime, atypical wake patterns such as 2P or $\mathrm{P} + \mathrm{S} $ can be observed, depending on the forcing frequency and the momentum coefficient, highlighting remarkable analogies with oscillating cylinders.

(Received May 19 2011)

(Reviewed December 08 2011)

(Accepted January 13 2012)

(Online publication March 01 2012)

Key Words:

  • flow control;
  • vortex flows;
  • wakes

Correspondence:

c1 Email address for correspondence: y.bury@isae.fr

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