20 February 2017 Shock wave strengthening through area reduction
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Proceedings Volume 10328, Selected Papers from the 31st International Congress on High-Speed Imaging and Photonics; 103281F (2017) https://doi.org/10.1117/12.2268868
Event: 31st International Congress on High-Speed Imaging and Photonics, 2016, Osaka, Japan
Abstract
Experiments were conducted in a shock tube in order to determine the increases in shock wave strength due to reductions in area. Previous work has shown that if the reduction is too sudden significant wave reflections occur and gains are limited. A variety of curved symmetrical contractions are used, made up of parabolic surfaces with different points of inflection. High-speed Schlieren imaging was used to characterize the wave patterns with particular emphasis on wave reflections. Greatest wave amplification is present when Mach reflection of the wave is not reached at all, and this was found to occur with parabolic profiles with inflection point at 60% of the profile length. Clear Mach reflection is evident with the inflection point at 40% and the post shock flow shows significant reflected waves with their associated losses. With an area reduction of 80% and a inflection point at 60% of the contraction, a typical result gives an increase in Mach number from 1.6 to 2.0, corresponding to a 61% increase in post-shock pressure. It is found that profiles with later inflection points provide a more gradual initial area change and allow weaker compression waves to develop which can significantly reduce or even avoid transition to Mach reflection.
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B. W. Skews, S. D. Subiah, R. T. Paton, "Shock wave strengthening through area reduction", Proc. SPIE 10328, Selected Papers from the 31st International Congress on High-Speed Imaging and Photonics, 103281F (20 February 2017); doi: 10.1117/12.2268868; https://doi.org/10.1117/12.2268868
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