Flow structure and optical beam propagation in high-Reynolds-number gas-phase shear layers and jets

We report on the structure of the scalar index-of-refraction field generate d by turbulent, gas-phase, incompressible and compressible shear layers and incompressible jets, and on associated beam-propagation aero-optical pheno mena. Using simultaneous imaging of the optical-beam distortion and the tur bulent-flow index-of-refraction field, wavefront-phase functions were compu ted for optical beams emerging from the turbulent region in these free-shea r flows, in an aero-optical regime producing weak wavefront distortions. Sp atial wavefront-phase behaviour is found to be dominated by the large-scale structure of these flows. A simple level-set representation of the index-o f-refraction field in high-Reynolds-number, incompressible shear lavers is found to provide a good representation of observed wavefront-phase behaviou r, indicating that the structure of the unsteady outer boundaries of the tu rbulent region provides the dominant contributions.