Aero-Optical Measurements in a Turbulent, Subsonic Boundary Layer at Different Elevation Angles

This paper describes a recent investigation of aero-optical properties for subsonic turbulent boundary layers on a flat plate. Laser propagation through the boundary layer at several oblique elevation angles, Mach numbers, and boundary layer displacement thicknesses was investigated. A simple model is proposed that incorporates the oblique angle dependence into an existing scaling relationship. Both single and double boundary layers were investigated and the levels of optical distortions for propagation normal to the wall were found to be in good agreement with the refined scaling relationship. These new experimental data allowed us to both refine the scaling-relationship constant and reduce the error in the measurement below those presented in previous papers.