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Shock-induced mixing of a light-gas cylinder

Jacobs, J. W. (1992) Shock-induced mixing of a light-gas cylinder. Journal of Fluid Mechanics, 234 . pp. 629-649. ISSN 0022-1120. doi:10.1017/S0022112092000946.

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Experiments have been carried out to quantify the mixing induced by the interaction of a weak shock wave with a cylindrical volume of a gas (helium) that is lighter than its surroundings (air). In these experiments a round laminar jet was used to produce the light-gas cylinder, and planar laser-induced fluorescence (PLIF), utilizing a fluorescent tracer (biacetyl) mixed with the helium, was used to visualize the flow. These techniques provide a higher quality of flow visualization than that obtained in previous investigations. In addition, the PLIF technique could be used for the measurement of species concentration. The distortion of the helium cylinder produced by the passing shock wave was found to be similar to that displayed by images from previous experimental and computational investigations. The downstream displacement of several points on the boundary of the light-gas cylinder are measured and agree reasonably well with the results of earlier experimental and theoretical studies as well. Because the mixing process causes the helium originally contained within the cylinder to be dispersed into the surrounding air, the PLIF image area inside the contour at one half the maximum concentration of the fluorescent tracer decreases as the two gases mixed. The change in this area is used as a measure of the mixing rate, and it is found that the time rate of change of this area divided by the area of the initial jet is approximately -0.7 × 10^3 s^-1.

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Additional Information:Copyright © 1992 Cambridge University Press. Reprinted with permission. (Received 14 September 1990 and in revised form 18 June 1991) The author would like to acknowledge Professors F. E. Marble and E. E. Zukoski for initiating the study of shock-enhanced mixing, and the subsequent shock tube experiments to study the mixing of helium inhomogeneities, of which this research was a part. The author is indebted to Professors Marble and Zukoski as well as Professor B. Sturtevant for their help, guidance and support with this research. Credit is due to Dr. R. Miake-Lye for his help with the laser-induced fluorescence system, and to Dr L. Hill, and Professors A. Glezer and C. H. K. Williamson their helpful comments and suggestions during the preparation of this paper. This work was supported by the Air Force Office of Scientific Research contract F49620-C-0113, monitored by Dr J. Tishkoff. In addition, during 1987 and 1988 the author was supported by a Weizmann Fellowship.
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Deposited On:26 Sep 2006
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