Response of plane shear layers and wakes to strong three‐dimensional disturbances

TLDR: In this paper, shear layers and wakes formed downstream of a splitter plate whose trailing edge has spanwise variations were briefly explored using the reacting flow visualization technique, showing that the global structure of the shear layer quickly forgets the initial perturbations, while the wake remembers them.

Abstract: Shear layers and wakes formed downstream of a splitter plate whose trailing edge has spanwise variations were briefly explored using the reacting flow visualization technique. A fundamental difference in behavior was observed between the two types of flows. The shear layer (which has only one sign of mean vorticity) rapidly forms its characteristic two‐dimensional vortex structures, whereas, in contrast, the wake (which has both signs of mean vorticity) forms closed vortex loops. These loops do not grow appreciably in the spanwise direction over the test section length, even though the transverse growth is comparable to the two‐dimensional wake behavior. The global structure of the shear layer quickly forgets the initial perturbations, while the wake remembers them. The results strongly suggest that the presence of only one or both signs of mean vorticity in these plane turbulent flows has a fundamental bearing on the spanwise structure and stability of the vorticity field.