Journal ArticleDOI
Absolute instability of the Gaussian wake profile
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TLDR
In this paper, the authors investigated the effect of viscosity on the local absolute instability of a family of wake profiles with a Gaussian velocity distribution and found that the effects of visco-viscosity were weak for values of the wake Reynolds number, based on the center-line velocity defect and the wake halfwidth.Abstract:
Linear 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, ie, 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 38read more
Citations
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Journal ArticleDOI
Local and global instabilities in spatially developing flows
TL;DR: In this article, a review of recent developments in the hydro- dynamic stability theory of spatially developing flows pertaining to absolute/convective and local/global instability concepts is presented.
Journal ArticleDOI
The absolute and convective nature of instability in two-dimensional wakes at low Reynolds numbers
TL;DR: The linear parallel and incompressible stability of a family of bluff-body wake profiles is studied at Reynolds numbers close to the onset of Karman vortex shedding as discussed by the authors, which confirms the qualitative model prediction of Chomaz, Huerre, and Redekopp.
Journal ArticleDOI
On management and control of turbulent shear flows
H. E. Fiedler,H. H. Fernholz +1 more
TL;DR: In this article, a major body of the available knowledge on flow control in separated and wall bounded turbulent flows is compiled and a brief introduction of the basics of control theory and of the major flow structures and their stability characteristics are discussed.
Journal ArticleDOI
The vibrating ribbon problem revisited
David E. Ashpis,Eli Reshotko +1 more
TL;DR: In this article, a revised formal solution of the vibrating ribbon problem of hydrodynamic stability is presented, which is modified by application of the Briggs method and a careful treatment of the complex double Fourier transform inversions.
Journal ArticleDOI
Absolute and convective instability of a cylinder wake
X. Yang,Abdelfattah Zebib +1 more
TL;DR: In this article, the stability behavior of a circular cross-section cylinder's wake at Reynolds number values of up to 45 is investigated by means of local linear stability theory, and the steady-wake profiles computed are Navier-Stokes solutions of a uniform, incompressible viscous flow around a cylinder obtained by a spectral method.
References
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Journal ArticleDOI
Absolute and convective instabilities in free shear layers
TL;DR: The absolute or convective character of inviscid instabilities in parallel shear flows can be determined by examining the branch-point singularities of the dispersion relation for complex frequencies and wavenumbers.
Journal ArticleDOI
Local instability characteristics and frequency determination of self-excited wake flows
TL;DR: In this article, it was shown that the shedding frequency of the self-excited vortex shedding process is governed by a resonance-like mechanism, which leads to a bifurcation condition (direct resonance condition) of the local instability eigenvalue.
Journal ArticleDOI
The generation of capillary instabilities on a liquid jet
S. J. Leib,Marvin E. Goldstein +1 more
TL;DR: In this paper, the coupling between imposed disturbances and capillary instabilities on a liquid jet is examined, and it is shown that in most physical situations the forcing produces neutral waves, which can then turn into growing waves as the profile relaxes or may be amplified nonlinearly by a mechanism of the type considered by Akylas and Benney (1980).