TY - JOUR
T1 - An experimental study of organized motions in the turbulent plane mixing layer
AU - Hussain, A. K.
AU - Zaman, K. B.
N1 - Copyright:
Copyright 2016 Elsevier B.V., All rights reserved.
PY - 1985/10
Y1 - 1985/10
N2 - Large-scale coherent structures in a large, single-stream plane mixing layer of air have been investigated experimentally. The unforced, initially fully turbulent mixing layer rolls up into organized structures whose average passage frequency fmat any downstream distance x from the lip depends on x. These structures are detected for the entire length of the measurement, i.e. up to x = 3m or 5OOOθe. The Strouhal number Stθ(= fmθ/Ue) is observed to be a constant (« 0.024) at all x. θeand θ are, respectively, the exit and local momentum thicknesses of the mixing layer, and Ueis the free-stream velocity. (The entrainment velocity on the zero-speed side is found to be 0.032Ue.) The coherent-structure properties are educed in the developing and self-preserving regions of the mixing layer using an optimized conditional-sampling method, triggered on the peaks of a local reference ũ-signal obtained from the high-speed edge of the layer. Sectional-plane contours of the properties of the structure such as coherent vorticity, Reynolds stress and production reveal that the structure formation and evolution are complete by x = 5OOθebeyond which the structure achieves an ‘equilibrium’ state as defined by the structure properties.
AB - Large-scale coherent structures in a large, single-stream plane mixing layer of air have been investigated experimentally. The unforced, initially fully turbulent mixing layer rolls up into organized structures whose average passage frequency fmat any downstream distance x from the lip depends on x. These structures are detected for the entire length of the measurement, i.e. up to x = 3m or 5OOOθe. The Strouhal number Stθ(= fmθ/Ue) is observed to be a constant (« 0.024) at all x. θeand θ are, respectively, the exit and local momentum thicknesses of the mixing layer, and Ueis the free-stream velocity. (The entrainment velocity on the zero-speed side is found to be 0.032Ue.) The coherent-structure properties are educed in the developing and self-preserving regions of the mixing layer using an optimized conditional-sampling method, triggered on the peaks of a local reference ũ-signal obtained from the high-speed edge of the layer. Sectional-plane contours of the properties of the structure such as coherent vorticity, Reynolds stress and production reveal that the structure formation and evolution are complete by x = 5OOθebeyond which the structure achieves an ‘equilibrium’ state as defined by the structure properties.
UR - http://www.scopus.com/inward/record.url?scp=0022144433&partnerID=8YFLogxK
U2 - 10.1017/S0022112085003111
DO - 10.1017/S0022112085003111
M3 - Article
AN - SCOPUS:0022144433
VL - 159
SP - 85
EP - 104
JO - Journal of Fluid Mechanics
JF - Journal of Fluid Mechanics
SN - 0022-1120
ER -