A Generalized Approach to Selecting, Designing, and Constructing Conformal, Optical Windows for Wind Tunnels

Conventional wind tunnels are designed to provide test conditions for models while incorporating required diagnostics. As optical diagnostics become more sophisticated, the requirements on optical access become more demanding. Flat windows and their mountings on curved cell walls can adversely affect the flows in these tunnels, not only affecting the test conditions themselves but also complicating optical diagnostics. Problems include aberrations, losses, multiple reflections, window contamination, effects on the flow and boundary layer, and many others. Solutions to these problems vary widely. Conformal opticals can reduce effects on the flow, but curved optics introduce new problems such as high cost and aberrations. This proposal offers a generalized approach to the selection and production of conformal optical elements. The approach will be applicable to a wide variety of requirements imposed by different diagnostic techniques. An optics code will be selected and adapted for this application to provide specifications for the window optical characteristics which can be assessed imediately. A library of aberration correction procedures, materials, and mounting and mechancial options will be provided. Including refractive and diffractive optics. Specific cases of duct/test cell walls include both cylindrical and compound curvature.