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Evolution of the air/SF6 turbulent mixing zone for different lengths of SF6: shock tube visualizations and 3D simulations

Haas, Jean-François and Griffond, Jérôme and Souffland, Denis and Bouzgarrou, Ghazi and Bury, Yannick and Jamme, Stéphane Evolution of the air/SF6 turbulent mixing zone for different lengths of SF6: shock tube visualizations and 3D simulations. (2015) In: Proceedings of APS-DFD Annual Meeting, 22 November 2015 - 24 November 2015 (Boston, United States).

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A turbulent mixing zone (TMZ) is created in a vertical shock tube (based in ISAE DAEP) when a Mach 1.2 shock wave in air accelerates impulsively to 70 m/s an air/SF6 interface. The gases are initially separated by a thin nitrocellulose membrane maintained at and parallel to the shock by two wire grids. The upper grid (SF6 side) of square mesh spacing hu 1.8 or 12.1 mm is expected to seed perturbation for the Richtmyer-Meshkov instability (RMI) while the lower grid with hl 1 mm is needed to prevent the membrane from bulging prior to the shot. The experiments were carried out for different lengths L of SF6 between the initial interface and the shock tube's end plate : 10, 15, 20, 25 and 30 cm. The time resolved Schlieren image processing based on space and frequency filtering yields similar evolution for the TMZ thickness. Before reshock, the thickness grows initially fast then slows down and reaches different values (10 to 14 mm) according to L. Soon after reshock, the TMZ thickness growths rate is 21 mm/ms independently of L and hu. Numerical Schlieren images gen- erated from 3D numerical simulations (performed at CEA DAM IDF) are analyzed as the experimental ones for L 15 and 25 cm and for hu 1.8 and 12.1 mm. The very weak experimental dependence on hu is not obtained by simulation as expected from dimensional reasoning. This discrepancy remains paradoxical.

Item Type:Conference or Workshop Item (Poster)
Audience (conference):International conference without published proceedings
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Institution:Université de Toulouse > Institut Supérieur de l'Aéronautique et de l'Espace - ISAE-SUPAERO (FRANCE)
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Deposited On:04 Dec 2015 14:00

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