Methods for Reducing Turbulent Flow Aero-Optical Distortion.

Methods for reducing the aero-optical distortion which affects jet-cooled seeker windows on high-speed, endo-atmospheric interceptors were studied. Reductions in turbulence were achieved by curving the shear layer in the streamwise direction. This type of curvature corresponds to a window whose outer surface is convex in the axial direction. For a case with moderate curvature, the peak shear stress and density fluctuations were reduced by 85 compared to an otherwise similar flat shear layer. The optical properties of the shear layers were evaluated using a simple ray-tracing method, and the aero-optical distortion was significantly reduced by the stabilizing curvature. Another control concept that was tested involved lateral convergence imposed upon the shear layer. This concept was unsuccessful from an aero-optics view point because the turbulent shear stress roughly doubled relative to the unmodifled shear layer.... Turbulence, optical distortion, Turbulence control, Large eddy simulation.