Aero-optical measurements of a zero-pressure-gradient, supersonic boundary layer along the test-section wall at M 2:0 were performed using a Malley probe. The Malley probe captured both the amplitude of optical distortions and the convective speed. The convective speed of the optically active structures inside the supersonic boundary layer was found to be 0.84 of the freestream speed. The deflection-angle spectra were found to collapse with the local displacement thickness. The streamwise correlation function for the supersonic boundary layer revealed the presence of a pseudoperiodic structure with the typical size of 1.5 of the local boundary-layer thickness. A new model was developed to describe aero-optical effects of both the subsonic and the supersonic boundary layers. Finally, this new model and several other theoretical scalings were tested in the attempt to collapse both subsonic and supersonic boundary-layer aero-optical results.

Effects of direct small-scale actuation on aerodynamic and aero-optical characteristics of flow over a hemisphereon-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 10 6 (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.

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