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Unsteady shock propagation in a steady flow nozzle expansion

Published online by Cambridge University Press:  26 April 2006

R. J. Stalker  and
N. R. Mudford
R. J. Stalker
Affiliation:
Department of Mechanical Engineering, University of Queensland, Brisbane. Qld 4072. Australia
N. R. Mudford
Affiliation:
Department of Physics and Theoretical Physics, Australian National University, Canberra, ACT 2601, Australia Present address: Department of Mechanical Engineering, University College, University of New South Wales, Australian Defence Force Academy, Northcott Drive, Campbell, ACT 2601, Australia.
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Abstract

The flow field produced when a strong shock wave propagates into a steady flow expansion has been investigated numerically, experimentally and analytically. The experiments were conducted with a shock tube which was modified to allow steady flow to be established in a hypersonic nozzle prior to arrival of the shock. It has been found that the axial density distribution associated with the prior steady flow allows the unsteady flow following the nozzle primary starting shock to accelerate from supersonic to hypersonic speeds, whereas a uniform density distribution causes it to decelerate to subsonic speeds. The prior steady flow also allows the starting shock system to propagate through the nozzle a t nearly the same velocity as the incident primary shock, and therefore provides a convenient method of ensuring rapid steady flow initiation in shock tunnel nozzles. The analysis shows that the flow behaviour can be understood in terms of two approximate models. The first is applicable to a wide range of flow conditions, and allows calculation of the trajectory of the centre of mass of the starting shock system. The second is applicable to cases involving a prior steady flow, and predicts detailed features of the flow structure.

Type
Research Article
Information
Journal of Fluid Mechanics , Volume 241 , August 1992 , pp. 525 - 548
Copyright
© 1992 Cambridge University Press

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