Abstract
Nonintrusive optical schemes are preferred for quantitative flow diagnostics. Shadow-casting scheme is one of the flow diagnostic techniques in which the projected shadow of a random-dot pattern mask reveals the flow information under the observation of the interrogating beam. Any variation in the flow field is seen as a change in position of the casted shadows of the mask which are calculated by cross-correlation scheme. The main downfall of such data processing schemes is the time requirement to process information, which has been targeted in this manuscript. The random-dot pattern mask is replaced with a 2D cosine grid, and Fourier data processing scheme is introduced to reveal orthogonal gradients of the flow field. A preliminary demonstration of the technique has been performed in hypersonic shock tunnel (HST2) facility using a hemispherically shaped test model placed in the flow field at Mach 8.83. Significant improvement in processing speed is observed while dealing with such data for recovering orthogonal flow gradients. The calculated slopes are further used in tomographic reconstruction for quantitative analysis of the flow around the test model.
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Medhi, B., Khatta, A., Hegde, G.M., Reddy, K.P.J., Roy, D., Vasu, R.M. (2017). Improved Flow Visualization for Fast Recovery of Flow Gradients in Shadow-Casting Technique. In: Ben-Dor, G., Sadot, O., Igra, O. (eds) 30th International Symposium on Shock Waves 2. Springer, Cham. https://doi.org/10.1007/978-3-319-44866-4_119
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DOI: https://doi.org/10.1007/978-3-319-44866-4_119
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