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Interaction of weak shock waves with cylindrical and spherical gas inhomogeneities

Haas, J.-F. and Sturtevant, B. (1987) Interaction of weak shock waves with cylindrical and spherical gas inhomogeneities. Journal of Fluid Mechanics, 181 . pp. 41-76. ISSN 0022-1120. http://resolver.caltech.edu/CaltechAUTHORS:20120626-083750257

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Abstract

The interaction of a plane weak shock wave with a single discrete gaseous inhomogeneity is studied as a model of the mechanisms by which finite-amplitude waves in random media generate turbulence and intensify mixing. The experiments are treated as an example of the shock-induced Rayleigh-Taylor instability. or Richtmyer-Meshkov instability, with large initial distortions of the gas interfaces. The inhomogeneities are made by filling large soap bubbles and cylindrical refraction cells (5 cm diameter) whose walls are thin plastic membranes with gases both lighter and heavier than the ambient air in a square (8.9 cm side shock-tube text section. The wavefront geometry and the deformation of the gas volume are visualized by shadowgraph photography. Wave configurations predicted by geometrical acoustics, including the effects of refraction, reflection and diffraction, are compared to the observations. Departures from the predictions of acoustic theory are discussed in terms of gasdynamic nonlinearity. The pressure field on the axis of symmetry downstream of the inhomogeneity is measured by piezoelectric pressure transducers. In the case of a cylindrical or spherical volume filled with heavy low-sound-speed gas the wave which passes through the interior focuses just behind the cylinder. On the other hand, the wave which passes through the light high-sound-speed volume strongly diverges. Visualization of the wavefronts reflected from and diffracted around the inhomogeneities exhibit many features known in optical and acoustic scattering. Rayleigh-Taylor instability induced by shock acceleration deforms the initially circular cross-section of the volume. In the case of the high-sound-speed sphere, a strong vortex ring forms and separates from the main volume of gas. Measurements of the wave and gas-interface velocities are compared to values calculated for one-dimensional interactions and for a simple model of shock-induced Rayleigh-Taylor instability. The circulation and Reynolds number of the vortical structures are calculated from the measured velocities by modeling a piston vortex generator. The results of the flow visualization are also compared with contemporary numerical simulations.


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http://dx.doi.org/10.1017/S0022112087002003 DOIUNSPECIFIED
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=393375PublisherUNSPECIFIED
Additional Information:© 1987 Cambridge University Press. Received 26 February 1986 and in revised form 10 December 1986. Published Online April 21 2006. This work was supported by the National Science Foundation under Grant Number MEA 81-20092.
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Record Number:CaltechAUTHORS:20120626-083750257
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20120626-083750257
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:32076
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:27 Jun 2012 20:13
Last Modified:26 Dec 2012 15:23

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