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The bifurcation of a hot round jet to limit-cycle oscillations
Surya Raghu,Peter A. Monkewitz +1 more
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In this article, the onset of self-excited or limit cycle oscillations in an axisymmetric hot jet is studied experimentally as the jet density is systematically decreased below the value at which absolute instability first appears in the potential core region.Abstract:
The onset of self‐excited or limit‐cycle oscillations in an axisymmetric hot jet is studied experimentally as the jet density is systematically decreased below the value at which absolute instability first appears in the potential core region By transient measurements at different supercritical jet densities, this bifurcation is demonstrated to be of the Hopf type That is, close to the critical density, the oscillation amplitude at a fixed point in space is shown to be described by a Landau equation All coefficients of the equation, ie, linear temporal growth rate, linear frequency, and the Landau constant, are determinedread more
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Self-excited oscillations in the wake of two-dimensional bluff bodies and their control
TL;DR: In this article, the onset of Karman-vortex shedding is studied experimentally in the wake of different two-dimensional bluff bodies, namely an oblong cylinder, circular cylinders and plates of rectangular cross-section.
Journal ArticleDOI
A numerical and theoretical study of the first Hopf bifurcation in a cylinder wake
TL;DR: In this paper, the first Hopf bifurcation of the infinite cylinder wake is analyzed theoretically and by direct simulation, and it is shown that a decomposition into a series of harmonics is a convenient theoretical and practical tool for this investigation.
Journal ArticleDOI
The instability and breakdown of a round variable-density jet
TL;DR: In this paper, the authors studied the instability and the subsequent breakdown of axisymmetric jets of helium/air mixtures emerging into ambient air, and found that the overall structure of the oscillating mode repeats itself with extreme regularity, and that the high degree of repeatability, in association with a strong pairing process, leads to abnormally large centreline velocity fluctuation.
Journal ArticleDOI
A Century of Turbulence
John L. Lumley,Akiva M. Yaglom +1 more
TL;DR: A brief, superficial survey of some very personal nominations for high points of the last hundred years in turbulence can be found in this paper, where some conclusions can be dimly seen: turbulence does not appear to have a pyramidal structure, like the best of physics.
Journal ArticleDOI
Forcing of self-excited round jet diffusion flames
TL;DR: In this article, two types of round jet are examined under acoustic forcing and the authors focus on the heat release of the jet diffusion flame, which oscillates at the same natural frequency as the bulging mode.
References
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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
Bénard-von Kármán instability: transient and forced regimes
M. Provansal,C. Mathis,L. Boyer +2 more
TL;DR: In this article, the wake of a circular cylinder near the oscillation threshold is investigated by means of a laser probe, and the Stuart-Landau law is used to explain free-oscillating regimes.
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Self-excited oscillations and mixing in a heated round jet
TL;DR: In this article, an axisymmetric hot-air jet discharging into cold ambient air is investigated experimentally and it is demonstrated by several different experiments that, for sufficiently low Reynolds number and a ratio of jet exit to ambient density below approximately 0.7, global oscillations of the "jet column" become self-excited, a behaviour which is related to local absolute instability in the potential core region.
Journal ArticleDOI
Absolute instability in hot jets
Peter A. Monkewitz,Kiho D. Sohn +1 more
TL;DR: In this paper, a linear inviscid stability of heated compressible axisymmetric jets is examined, focusing on the impulse response of the flow, and the results suggest that a self-excited global resonance may dominate the heated jet response in situations of practical interest.
Journal ArticleDOI
Absolute instability in variable density round jets
TL;DR: In this paper, the properties of round jets of different densities issuing into the ambient air were investigated and it was shown that these jets have two types of behaviour depending on the density ratio between the jet and the ambient fluids.