Digital analysis of shadowgraph images for statistical index of refraction (density) turbulent fluctuation properties in high-speed flow
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A non-intrusive method for obtaining index of refraction (density) turbulent fluctuation levels from shadowgraph photographs of high-speed flows is presented. The application of modern image processing techniques to shadowgraphs allowed critical compressible turbulence data to be acquired accurately and easily. The techniques were applied to supersonic free mixing (shear) layers, as an example application. The flow field was designed to represent a near full-scale supersonic combustion chamber. The optically measured density fluctuation levels were compared to those measured by an intrusive cross-wire anemometry method, and excellent agreement was found. 1995.