Interactions of a Low-Aspect-Ratio Cantilevered Dynamic Pin with a Boundary Layer

摘要

The interaction of a low-aspect-ratio finite-span pin with a laminar flow over a flat plate was investigated experimentally. The pin was either static or dynamically oscillated in the wall-normal direction at a driving frequency that was either equivalent to the natural shedding frequency or its subharmonic. The mean height of the pin was either equal to 1 or 1.5 times the local boundary-layer thickness. The study focused on the formation and development of two main vortical structures: the arch-type vortex and the horseshoe vortex. It was shown that the arch vortex combined with the counter-rotating horseshoe vortex. The shedding of this coupled phenomenon was investigated under static and dynamic conditions to provide comparisons between their corresponding flowfield behaviors. Under dynamic conditions, the arch-type vortex periodically shed from the pin's free end and advected downstream, interacting with the horseshoe vortex, which resulted in complex, three-dimensional, and time-periodic flow patterns. The dynamics of these flow structures were determined to be dependent upon the driving frequency and actuation amplitude.