Abstract
The Calcium-K Eclipse Background-Oriented Schlieren experiment was performed as a proof of concept test to evaluate the effectiveness of using the solar disk as a background to perform the Background-Oriented Schlieren (BOS) method of flow visualization. A ground-based imaging system was equipped with a Calcium-K line optical etalon filter to enable the use of the chromosphere of the sun as the irregular background to be used for BOS. A US Air Force T-38 aircraft performed three supersonic runs which eclipsed the sun as viewed from the imaging system. The images were successfully post-processed using optical flow methods to qualitatively reveal the density gradients in the flow around the aircraft.
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Acknowledgements
The authors thank the National Aeronautics and Space Administration Commercial Supersonics Technology Project for funding and support, National Aeronautics and Space Administration Armstrong Flight Research Center support personnel for enabling these flights, and Major Jonathan Orso and Colonel Glenn Graham of the US Air Force Test Pilot School for their skillful flying.
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Hill, M.A., Haering, E.A. Ground-to-air flow visualization using Solar Calcium-K line Background-Oriented Schlieren. Exp Fluids 58, 4 (2017). https://doi.org/10.1007/s00348-016-2285-7
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DOI: https://doi.org/10.1007/s00348-016-2285-7