Synthetic Jet Interaction with a Hybrid Actuator in a Laminar Boundary Layer

Experiments investigated the interaction of a 45-deg-pitched, finite-span, rectangular synthetic jet (SJ) upstream of a low-aspect-ratio circular cylinder (pin) with and without a jet-assisted surface-mounted actuator (JASMA) in a laminar boundary layer over a flat plate. The SJ generated a train of hairpin vortices that convected into the vicinity of the pin/JASMA downstream. The interaction was quantified using particle image velocimetry and stereoscopic particle image velocimetry at multiple planes, which were aggregated into a flowfield volume. The interaction of the SJ with the pin resulted in a breakup of the SJ vortices. Moreover, the centerline flowfield was similar to the wake of the pin alone, but outboard of the pin, the SJ locked the horseshoe vortices to its driving frequency. The interaction of the SJ with either the pin or the JASMA resulted in increased turbulent kinetic energy, prolonged streamwise vorticity, and increased downwash downstream. Additionally, the SJ/JASMA combination increased momentum injection into the boundary layer compared to the case when only the SJ was actuated. Results of this study are encouraging for application of the JASMA as a low-cost actuator to utilize naturally occurring turbulent vortical structures for more efficient separation control.