Pe. Dimotakis et al., Flow structure and optical beam propagation in high-Reynolds-number gas-phase shear layers and jets, J FLUID MEC, 433, 2001, pp. 105-134
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.