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Theory and computations for breakup of unsteady subsonic or supersonic separating flows

Smith, FT; Vickers, IP; (1994) Theory and computations for breakup of unsteady subsonic or supersonic separating flows. Journal of Fluid Mechanics , 268 147 - 173. 10.1017/S0022112094001308. Green open access

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This study of flow just beyond a breakaway-separation point presents a description of planar nonlinear unsteady effects over a fairly wide parameter range, for a subsonic or supersonic boundary layer at large Reynolds numbers. The inviscid model thus produced essentially contains a vortex sheet near the smooth solid surface, with local inner–outer interaction. The governing equations couple the eddy velocity and pressure with the thicknesses of the detached boundary layer and the eddy. The computational method presented here uses a new adaptive gridding technique intended to capture accurately the spiky solution behaviour that develops and to compare with theory. Analysis and computations point to a breakup in the solution, suggesting an explanation for the start of transition and possible turbulent reattachment as found experimentally. The influence of the detached boundary-layer thickness proves crucial. The type of finite-time breakup encountered is studied analytically and the criterion for its occurrence is highlighted. This is guided by a characteristic analysis for a special case. The finite-time breakup is similar in spirit to, although different in detail from, a nonlinear breakup proposed earlier by one of the authors for general unsteady interactive boundary layers and it suggests a wide application of that nonlinear breakup theory and its criterion. Comparisons between computations and theory are found to be supportive.

Type: Article
Title: Theory and computations for breakup of unsteady subsonic or supersonic separating flows
Open access status: An open access version is available from UCL Discovery
DOI: 10.1017/S0022112094001308
Publisher version: http://dx.doi.org/10.1017/S0022112094001308
Language: English
Additional information: © 1994 Cambridge University Press
UCL classification: UCL > School of BEAMS
UCL > School of BEAMS > Faculty of Maths and Physical Sciences
URI: http://discovery.ucl.ac.uk/id/eprint/82786
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