Abstract
The vortex structure in the periodically perturbed turbulent separated shear layer is experimentally investigated. The backward-facing step flow is chosen for the test case, where the perturbation has been introduced as a direct suction and injection at the step edge. In this study, the particle imaging velocimeter (PIV) has been applied to measure the flow field. The data processing has been performed by means of the phase-averaging, synchronized with the perturbation, so that the periodic motion associated with the perturbation is extracted. It is discovered that the large-scale vortices are introduced by the perturbation and these vortices are convected downstream successively. It is also revealed that these vortices have a major role on the increasing of Reynolds stress in the separated shear layer enabling in the enhancement of the momentum transfer that promotes reattachment.
