An investigation of large-scale structure in the similarity region of a two-dimensional turbulent jet

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Abstract
An experimental investigation of large-scale structural patterns in the similarity region of a two-dimensional turbulent jet was performed. Two-point correlation and coherence-based measurements obtained from both longitudinal and lateral component velocity fluctuations are, in general, supportive of the existence of an antisymmetric array of counterrotating vortices in the similarity region. Particularly graphic evidence is obtained from detailed isocorrelation contour maps that are presented. A novel method of determining structural convective velocity is developed and indicates the structural array propagates at 60% of the local centerline mean velocity. Very limited structural two dimensionality is exhibited in the direction of mean flow homogeneity and it is suggested that this is likely to be related to the existence of multiple coherent modes in the flow.