Aero-Optic Characterization of Supersonic Boundary Layers in the Trisonic Gasdynamic Facility

An aero-optic characterization of the empty tunnel test section wall boundary layers was conducted in the Air Force Research Laboratory’s Trisonic Gasdynamics Facility with freestream Mach numbers of 1.5, 1.9, 2.3 and 3.0. A Malley probe and Shack-Hartmann wavefront sensor were used to acquire spatially and temporally resolved wavefront data. At each Mach number, aero-optic data were acquired at multiple freestream densities and streamwise location in order to establish scaling relationships. The overall aberration levels ranged between 10-50 nm of rms Optical Path Difference (OPD) over a 3 cm viewing aperture and exhibited a linear dependence on freestream density, as expected. OPD was also observed to generally increase with downstream location, although not for every case tested. A companion paper (Ref. 13) examines the detailed spatio-temporal characteristics and scaling of the data.