Large-scale and small-scale turbulence structures in the intermediate wake of a two-dimensional normal plate

The properties of the velocity fluctuations in the wake of a normal flat plate were studied at eight heights downstream of it by decomposing the fluctuations into three components: the fundamental fluctuation, the large-scale deviation, and the small-scale fluctuation. The Reynolds number based on the free-stream velocity and the plate height was 23,000. The energy of the large-scale deviation was found to be much greater than that of the small-scale fluctuation. The former attained maxima at the center of the coherent vortex. The Reynolds shear stress associated with this deviation also attained maxima near the saddle points, demonstrating that the large-scale deviation is the major component of the velocity fluctuations in the intermediate wake. The energy of the small-scale structure is the smallest among the three components of the velocity fluctuations. Its maximum appears at a position off the vortex center.