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Absolute instability of the Gaussian wake profileLinear parallel-flow stability theory has been used to investigate the effect of viscosity on the local absolute instability of a family of wake profiles with a Gaussian velocity distribution. The type of local instability, i.e., convective or absolute, is determined by the location of a branch-point singularity with zero group velocity of the complex dispersion relation for the instability waves. The effects of viscosity were found to be weak for values of the wake Reynolds number, based on the center-line velocity defect and the wake half-width, larger than about 400. Absolute instability occurs only for sufficiently large values of the center-line wake defect. The critical value of this parameter increases with decreasing wake Reynolds number, thereby indicating a shrinking region of absolute instability with decreasing wake Reynolds number. If backflow is not allowed, absolute instability does not occur for wake Reynolds numbers smaller than about 38.
Document ID
19880033615
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Hultgren, Lennart S.
(NASA Lewis Research Center Cleveland, OH, United States)
Aggarwal, Arun K.
(Illinois Institute of Technology Chicago, United States)
Date Acquired
August 13, 2013
Publication Date
November 1, 1987
Publication Information
Publication: Physics of Fluids
Volume: 30
ISSN: 0031-9171
Subject Category
Fluid Mechanics And Heat Transfer
Accession Number
88A20842
Distribution Limits
Public
Copyright
Other

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