The convective velocity of large-scale structures in a turbulent two-dimensional jet

Some of the deterministic characteristics of the coherent structures in the similarity region of a two-dimensional jet were investigated experimentally.

The presence of the large-scale vortex-like structures within the flow field was confirmed with longitudinal velocity fluctuation cross-correlation measurements. The structures were found to have an asymmetric instantaneous distribution of longitudinal velocity fluctuation with streamwise periodicity and coherence over the entire width of the flow.

Structural passage frequencies at various streamwise stations were measured on the basis of two-point longitudinal velocity fluctuation cross-correlations. The streamwise variation of this frequency parameter was found to be compatible with the similarity scaling relationships for the two-dimensional jet. The structural convective velocity in the fully turbulent region was measured and found to be a unique percentage of the local mean centerline velocity. This is in contrast to the results of previous investigations where the structural convective velocity appeared to be functionally dependent on the cross-stream coordinate.