Fluidic Control of a Turret Wake: Aerodynamic and Aero-Optical Effects

Abstract

Effects of direct small-scale actuation on aerodynamic and aero-optical characteristics of flow over a hemisphere-on-cylinder turret model (D = 0.61 m) with a round 0.254-m-diam conformal optical aperture are investigated at M = 0.3 and Re D = 4.46 · 106 (with additional measurements at M = 0.4 and 0.5). Flow control is effected by arrays of piezoelectrically driven synthetic jet modules. The cumulative effect of the actuation is manifested by a concomitant delay of flow separation and active, dissipative suppression of turbulent motion downstream of separation. Effects of actuation on aero-optical distortions are assessed from the flow dynamics, using surface oil visualization, static pressure distributions, and hot-film measurements within the separated flow domain. In addition, the suppression of optical distortion across the separated flow is measured directly using a Malley probe over a range of elevation angles. These measurements show that for a fixed actuation level, the active suppression level of spectral components of the optical distortion is about 30% within a resolved frequency band 0.5 < f < 25 kHz at M = 0.3.