Accession Number : ADA263698

Title :   Methods for Reducing Turbulent Flow Aero-Optical Distortion.

Descriptive Note : Final rept. 1 Jun 92-30 Jun 93,

Corporate Author : NIELSEN ENGINEERING AND RESEARCH INC MOUNTAIN VIEW CA

Personal Author(s) : Childs, Robert E.

Report Date : 31 MAR 1993

Pagination or Media Count : 47

Abstract : 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.

Descriptors :   *INTERCEPTORS, *WINDOWS, *TURBULENT FLOW, *OPTICAL DETECTION, CONTROL, CURVATURE, DENSITY, DISTORTION, OPTICAL PROPERTIES, OPTICS, RAY TRACING, REDUCTION, SURFACES, TURBULENCE, VELOCITY, SHEAR STRESSES, EDDIES(FLUID MECHANICS), COOLING, TARGET DETECTION, COMPUTERIZED SIMULATION, VORTICES.

Subject Categories : Aerodynamics
      Optical Detection and Detectors
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE