Closed-Loop Active Flow Control of a Three-Dimensional Turret Wake

Abstract

An experimental study has been performed to investigate the wake of a three-dimensional turret with aspect ratio of 1.17 at a diameter-based Reynolds number of 5.5 × 10 5 . Stereoscopic particle image velocimetry was used to evaluate the spatial structure of the wake, and dynamic surface-pressure measurements were used to study the time-dependent behavior. The uncontrolled wake was seen to be strongly three-dimensional with two main structures on opposing sides of the center plane. Cross correlations from the surface pressure indicated that opposite sides of the wake had nearly zero correlation in time. With the application of active flow control, both the spatial structure and timedependent behavior of the wake were significantly altered. The downwash velocity along the center plane was seen to increase significantly, causing the wake to spread more rapidly near the support plate, and the spectra from the pressure sensors contained multiple peaks at different frequencies throughout the wake that were not seen in the baseline case. Closed-loop control achieved similar control authority as steady open-loop forcing, but with a 45% reduction in the mean jet-momentum coefficient. Nomenclaturereduced forcing frequency H = turret height Re D = diameter-based Reynolds number Sr D = diameter-based Strouhal number U = streamwise velocity component U J = suction-jet velocity U ∞ = freestream velocity V = wall-normal velocity component W = cross-stream velocity component x = streamwise coordinate y = wall-normal coordinate z = cross-stream coordinate ρ J = suction-jet density ρ ∞ = freestream density