Self-Sustained Oscillations of Impinging Free Shear Layers

Rockwell, D.; Naudascher, Eduard

doi:10.1146/annurev.fl.11.010179.000435

Cited by 561 publications

(242 citation statements)

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“…1,2 Flows in which self-sustained oscillations occur are (amongst others): jets issuing into a thin cavity, [3][4][5][6][7][8][9] the flow over backward facing steps, 10,11 and flows over cavities. [12][13][14][15] The self-sustained oscillations have a much lower frequency than those produced by shear layer instabilities.…”

Section: Introductionmentioning

confidence: 99%

Effects of electromagnetic forcing on self-sustained jet oscillations

et al. 2014

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The influence of electromagnetic forcing on self-sustained oscillations of a jet issuing from a submerged nozzle into a thin vertical cavity (width W much larger than thickness T) has been studied using particle image velocimetry. A permanent Lorentz force is produced by applying an electrical current across the width of the cavity in conjunction with a magnetic field from three permanent magnets across its thickness. As a working fluid a saline solution is used. The magnetic field is in the north-south-north configuration, such that the Lorentz force can be applied in an up-down-up configuration or in a down-up-down configuration by switching the direction of the electrical current. A critical Stuart number Nc was found. For N < Nc, the jet oscillates with a constant Strouhal number St, independent of the Reynolds number Re. For N > Nc and an oscillation enhancing up-down-up configuration of the Lorentz force, St grows with N as St \documentclass[12pt]{minimal}\begin{document}$\propto \sqrt{\mathrm{N}}$\end{document}∝N. In contrast, for N > Nc and an oscillation suppressing down-up-down configuration of the Lorentz force, all jet oscillations are suppressed.

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Section: Introductionmentioning

confidence: 99%

Effects of electromagnetic forcing on self-sustained jet oscillations

et al. 2014

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“…However, for nearly all oscillations in liquids, such as those investigated herein, L b is much smaller than the acoustic wavelength l, and therefore L b /l , , 1 such that the source and upstream perturbation propagation can be treated as purely hydrodynamic (Rockwell and Naudascher 1979).…”

Section: Investigations On Oscillating Cavity Flowmentioning

confidence: 95%

“…Studies of jet-edge, cavity-edge and mixing-layer-edge oscillations indicated that the oscillation frequency can reasonably be predicted for certain geometries (Rockwell and Naudascher 1979). The dimensionless frequency of oscillations is expressed in terms of the…”

Section: Investigations On Oscillating Cavity Flowmentioning

confidence: 99%

Water-surface oscillations in channels with axi-symmetric cavities

Meile

Boillat

Schleiss

2011

Journal of Hydraulic Research

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Transverse or longitudinal movements of a water body are observed for flows along cavities, river embayments, groyne fields or harbours. They are significant for certain flow conditions and geometrical properties. To study the effect of large-scale roughness on banks, 36 geometries of axi-symmetric, rectangular cavities were investigated in a laboratory flume under subcritical, turbulent free surface flow conditions. Significant movements of the water body were detected. The frequency of these periodic movements, identified by level and velocity observations, is in agreement with the natural frequency of the water body in a rectangular basin assuming the first-order mode of sloshing. Major movements of the water body, which lead to significant and periodic oscillations of the water surface, are avoided by excluding Strouhal numbers near 0.42 and 0.84. For low aspect cavity ratios, the periodic water-surface oscillations are insignificant if the flow reattaches to the sidewalls of the widened channel reach.

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“…The shear layer is also present over a rectangular cavity, but its evolution is modified by a presence of a strong feedback [14][15][16] as follows: the shear layer develops large-structures through the inflection velocity profile instability; they convect downstream and impinge on the back wall of the cavity. It creates strong acoustical waves which travel upstream inside the cavity and impose disturbances on the initial region of the shear layer, thus completing the feedback.…”

Section: B Cavity Flowmentioning

confidence: 99%

Simulation of Optical Distortions of Two-Dimensional Shear Layer Using Large Structure Model (LSM)

Gordeyev

Jumper

Trolinger

2006

44th AIAA Aerospace Sciences Meeting and Exhibit

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A simple weakly compressible discrete vortex Large Structure Model (LSM) to predict dynamic evolution of the subsonic compressible two-dimensional shear layer is presented. It was shown that LSM code correctly predicts the shear layer growth rate and structure evolution, as well as spectral content and amplitude of optical distortions imposed by the shear layer on the passing laser beam. Due to small number of vortices required to represent the shear layer dynamics, computational times are very short. Also, the model was successfully extended to predict optical aberrations in flows over rectangular cavities. This model was developed as an engineering tool to quickly estimate dynamical optical distortions from shear layers.

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Self-Sustained Oscillations of Impinging Free Shear Layers

Cited by 561 publications

References 0 publications

Effects of electromagnetic forcing on self-sustained jet oscillations

Effects of electromagnetic forcing on self-sustained jet oscillations

Water-surface oscillations in channels with axi-symmetric cavities

Simulation of Optical Distortions of Two-Dimensional Shear Layer Using Large Structure Model (LSM)

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