Shear layer behavior resulting from shock wave diffraction |
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Authors: | Email author" target="_blank">Beric?SkewsEmail author Craig?Law Adam?Muritala Sebastian?Bode |
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Institution: | (1) School of Mechanical, Industrial, and Aeronautical Engineering, University of the Witwatersrand, PO WITS, 2050 Johannesburg, South Africa |
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Abstract: | All previous studies on shock wave diffraction in shock tubes have spatial and temporal limitations due to the size of the
test sections. These limitations result from either the reflection of the expansion wave, generated at the corner, from the
top wall and/or of the reflection of the incident diffracted shock from the bottom wall of the test section passing back through
the region of interest. This has limited the study of the evolution of the shear layer and its associated vortex, which forms
a relatively small region of the flow behind the shock with an extent of only a few centimeters, and yet is a region of significant
interest. A special shock tube is used in the current tests which allow evolution of the flow to be examined at a scale about
an order of magnitude larger than in previously published results, with shear layer lengths of up to 250 mm being achieved
without interference from adjacent walls. Tests are presented for incident shock wave Mach numbers of nominally 1.3–1.5. Studies
have been undertaken with wall angles of 10, 20, 30 and 90°. Significant changes are noted as the spatial and temporal scale
of the experiment increases. For a given wall angle, the flow behind the incident shock is not self-similar as is usually
assumed. Both shear layer instability and the development of turbulent patches become evident, neither of which have been
noted in previous tests. |
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