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Unsteady shock wave dynamics

Published online by Cambridge University Press:  30 April 2008

P. J. K. BRUCE  and
H. BABINSKY
P. J. K. BRUCE
Affiliation:
Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK
H. BABINSKY
Affiliation:
Department of Engineering, University of Cambridge, Trumpington Street, Cambridge CB2 1PZ, UK
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Abstract

An experimental study of an oscillating normal shock wave subject to unsteady periodic forcing in a parallel-walled duct has been conducted. Measurements of the pressure rise across the shock have been taken and the dynamics of unsteady shock motion have been analysed from high-speed schlieren video (available with the online version of the paper). A simple analytical and computational study has also been completed. It was found that the shock motion caused by variations in back pressure can be predicted with a simple theoretical model. A non-dimensional relationship between the amplitude and frequency of shock motion in a diverging duct is outlined, based on the concept of a critical frequency relating the relative importance of geometry and disturbance frequency for shock dynamics. The effects of viscosity on the dynamics of unsteady shock motion were found to be small in the present study, but it is anticipated that the model will be less applicable in geometries where boundary layer separation is more severe. A movie is available with the online version of the paper.

JFM classification

Compressible Flows: Shock waves
Type
Papers
Information
Journal of Fluid Mechanics , Volume 603 , 25 May 2008 , pp. 463 - 473
Copyright
Copyright © Cambridge University Press 2008

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References

REFERENCES

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Bruce and Babinsky supplementary movie

Movie 1. High-speed schlieren video footage of a normal Mach 1.4 shock wave undergoing forced periodic oscillations at a frequency of 43 Hz, see figure 4 in the paper. The video is shown at 1/120th real time (true oscillation period is 23 ms). The amplitude of oscillation is 46 mm. The structure of the interaction between the shock and the tunnel floor boundary layer can be seen to vary through the cycle of motion.

Download Bruce and Babinsky supplementary movie(Video)
Video 7.2 MB