Aero-Optic Distortion Minimization using Active Flow Control

"A system that integrates the use of zero frequency and high frequency flow control is proposed to reduce aero-optic distortions by minimizing large-scale shear layer structures. An important measure of performance for a tactical laser system is theintensity of the beam on a target. The performance of these systems is degraded by index of refraction variations introduced by large-scale flow structures along a beam path. In this investigation, carefully chosen excitation will be used toartificially alter the development of a shear layer, leading to a suppression of large flow structures and systematic improvements to a tactical laser system. Experimental and computational investigation will quantify the effect of forcing on compressibleshear layers and provide scaling the results for Mach number and Reynolds number effects. Time resolved wavefront measurements, as well as Schlieren and hot-wire anemometer measurements, will be used to assess the impact of control on the distortion of alaser beam propagating through the shear layer in the compressible regime. Developed capability will enable tactical directed energy weapons, as well as offering new optical communications capabilities for high speed air travel."