The wake of a bluff body in highly pulsatile flow: effects of freestream inflow frequency

Bluff body wake dynamics in highly pulsatile flows are of interest due to their potential for complexity and sensitivity to flow parameters. Large fluctuations in freestream velocity occur in biological, geophysical, and engineering flows in a multitude of contexts, e.g. blood flow, speech production, coastal flows, gusting winds. Large amplitude freestream pulsatility has, in our prior studies, provided insight into bluff body wakes in general. In this study we focus on the effect of the frequency of the large-scale freestream fluctuations, spanning from vortex lock-in frequencies at the upper bound down to quasi-steady inflow. The bluff body studied is a surface-mounted hemisphere that protrudes out of the boundary layer. A series of direct numerical simulations (DNS) supplement experimental studies performed using planar particle image velocimetry and hot-wire anemometry in a low-speed, pulsatile wind tunnel. Characterizations of freestream penetration, wake turbulence, and qualitative wake regimes through a sweep of inflow frequencies will be presented and compared.