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Turbulent spots in a channel: large-scale flow and self-sustainability

Published online by Cambridge University Press:  14 August 2013

Grégoire Lemoult*
Affiliation:
Laboratoire de Physique et Mécanique des Milieux Hétérogènes (PMMH), UMR CNRS 7636, ESPCI, UPMC, Paris Diderot, 10 rue Vauquelin, 75005 Paris, France
Jean-Luc Aider
Affiliation:
Laboratoire de Physique et Mécanique des Milieux Hétérogènes (PMMH), UMR CNRS 7636, ESPCI, UPMC, Paris Diderot, 10 rue Vauquelin, 75005 Paris, France
José Eduardo Wesfreid
Affiliation:
Laboratoire de Physique et Mécanique des Milieux Hétérogènes (PMMH), UMR CNRS 7636, ESPCI, UPMC, Paris Diderot, 10 rue Vauquelin, 75005 Paris, France
*
Email address for correspondence: gregoire.lemoult@espci.fr

Abstract

Using a large-time-resolved particle image velocimetry field of view, a developing turbulent spot is followed in space and time in a rectangular channel flow for more than 100 advective time units. We show that the flow can be decomposed into a large-scale motion consisting of an asymmetric quadrupole centred on the spot and a small-scale part consisting of streamwise streaks. From the temporal evolution of the energy of the streamwise and spanwise velocity perturbations, it is suggested that a self-sustaining process can occur in a turbulent spot above a given Reynolds number.

Information

Type
Rapids
Copyright
©2013 Cambridge University Press 

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Lemoult et al. supplementary movie

This movie presents the instantaneous small scales streamwise fluctuations $\tilde{u}$ for $Re=2000$ and $0<t^*<170$. Arrows represents the large scale flow field. Due to the finite size of the observation window, the gray area at the start and end, corresponds to boundaries of this window.

Download Lemoult et al. supplementary movie(Video)
Video 4.2 MB