https://doi.org/10.1140/epje/i2014-14025-2
Regular Article
Turbulent spots in channel flow: An experimental study
Large-scale flow, inner structure and low-order model
1
Laboratoire de Physique et Mécanique des Milieux Hétérogènes (PMMH), UMR CNRS 7636, ESPCI, UPMC, Paris Diderot, 10 rue Vauquelin, 75005, Paris, France
2
Inst Aeronaut & Appl Mech, Warsaw University of Technology, PL-00665, Warsaw, Poland
* e-mail: gregoire.lemoult@espci.fr
Received:
31
July
2013
Revised:
2
November
2013
Accepted:
11
April
2014
Published online:
25
April
2014
We present new experimental results on the development of turbulent spots in channel flow. The internal structure of a turbulent spot is measured, with Time Resolved Stereoscopic Particle Image Velocimetry. We report the observation of travelling-wave-like structures at the trailing edge of the turbulent spot. Special attention is paid to the large-scale flow surrounding the spot. We show that this large-scale flow is an asymmetric quadrupole centred on the spot. We measure the time evolution of the turbulent fluctuations and the mean flow distortions and compare these with the predictions of a nonlinear reduced order model predicting the main features of subcritical transition to turbulence.
Key words: Topical issue: Irreversible Dynamics: A topical issue dedicated to Paul Manneville
© EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg, 2014