Coherent Structures in the Similarity Region of a Two-Dimensional Turbulent Jet: A Vortex Street

摘要

The characteristics of the coherent structures of a plane jet were evaluated experimentally and with a kinematic numerical representation. Distributions of intermittency and interface crossing frequency were measured for 10 less than or equal to x/D less than or equal to 60. These properties, including the maximum interface crossing frequency, were found to scale as self-preserving flow variables. Spatially coherent patterns within the turbulent velocity field were evaluated utilizing two point velocity correlation measurements. From these, it was found that the instantaneous velocity fluctuation distributions are antisymmetric with respect to the centerline and coherent over the entire width of the flow field. In addition, the patterns are periodic in the streamwise direction. The two-dimensionality of the large structures was evaluated through the comparison of longitudinal and vertical integral length scales derived from correlations in both the fully turbulent zone and the intermittent region.