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Dynamical separation of spherical bodies in supersonic flow

Laurence, S. J. and Parziale, N. J. and Deiterding, R. (2012) Dynamical separation of spherical bodies in supersonic flow. Journal of Fluid Mechanics, 713 . pp. 159-182. ISSN 0022-1120. https://resolver.caltech.edu/CaltechAUTHORS:20130103-080706150

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Abstract

An experimental and computational investigation of the unsteady separation behaviour of two spheres in Mach-4 flow is carried out. The spherical bodies, initially contiguous, are released with negligible relative velocity and thereafter fly freely according to the aerodynamic forces experienced. In experiments performed in a supersonic Ludwieg tube, nylon spheres are initially suspended in the test section by weak threads which are detached by the arrival of the flow. The subsequent sphere motions and unsteady flow structures are recorded using high-speed (13 kHz) focused shadowgraphy. The qualitative separation behaviour and the final lateral velocity of the smaller sphere are found to vary strongly with both the radius ratio and the initial alignment angle of the two spheres. More disparate radii and initial configurations in which the smaller sphere centre lies downstream of the larger sphere centre each increases the tendency for the smaller sphere to be entrained within the flow region bounded by the bow shock of the larger body, rather than expelled from this region. At a critical angle for a given radius ratio (or a critical radius ratio for a given angle), transition from entrainment to expulsion occurs; at this critical value, the final lateral velocity is close to maximum due to the same ‘surfing’ effect noted by Laurence & Deiterding (J. Fluid Mech., vol. 676, 2011, pp. 396–431) at hypersonic Mach numbers. A visualization-based tracking algorithm is used to provide quantitative comparisons between the experiments and high-resolution inviscid numerical simulations, with generally favourable agreement.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1017/jfm.2012.453 DOIArticle
ORCID:
AuthorORCID
Parziale, N. J.0000-0001-9880-1727
Additional Information:© 2012 Cambridge University Press. Received 27 January 2012; revised 15 July 2012; accepted 10 September 2012; first published online 26 October 2012. The authors wish to thank J. E. Shepherd, whose financial support made the experiments possible, and H. G. Hornung, with whom we had useful discussions.
Group:GALCIT
Subject Keywords:aerodynamics; flow-structure interactions; shock waves
Record Number:CaltechAUTHORS:20130103-080706150
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20130103-080706150
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:36130
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:10 Jan 2013 19:39
Last Modified:03 Oct 2019 04:35

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