Aero-optical effects in free and wall-bounded turbulent compressible flows

The optical aberrations induced by turbulent compressible flows are a serious concern in airborne communication, imaging and optical systems because the quality of the laser beam degrades due to variations of the index of refraction along its path. The aero-optical aberrations produced by compressible flows are a direct consequence of the detailed physics of the flow. Time-accurate computational study of aero-optical distortions is performed based on large-eddy simulation technique because of its ability to account for the optical phase errors due to anisotropy of the flowfield and to resolve large-scale coherent structures at a reasonable computational cost. The results of numerical simulation of turbulent compressible flows in a flat plate boundary layer, free mixing layer and free jet provide general statistics of optical distortions by examining the time-averaged intensity pattern and instantaneous flowfield. The developed computational tools and results are beneficial in design and optimization of optical systems, where the control of laser beam propagation is an important problem, and coherent optical adaptive equipment and techniques based on the optical detection of light-scattering properties of the flow.