We report on the structure of the scalar index-of-refraction field generated by turbulent,
gas-phase, incompressible and compressible shear layers and incompressible
jets, and on associated beam-propagation aero-optical phenomena. Using simultaneous
imaging of the optical-beam distortion and the turbulent-flow index-of-refraction field,
wavefront-phase functions were computed for optical beams emerging
from the turbulent region in these free-shear flows, in an aero-optical regime producing
weak wavefront distortions. Spatial wavefront-phase behaviour is found to be
dominated by the large-scale structure of these flows. A simple level-set representation
of the index-of-refraction field in high-Reynolds-number, incompressible shear layers
is found to provide a good representation of observed wavefront-phase behaviour,
indicating that the structure of the unsteady outer boundaries of the turbulent region
provides the dominant contributions.