Extraction and Reconstruction of Individual Vortex-Shedding Mode from Bistable Flow

Lei Wang; Li-Hao Feng

doi:10.2514/1.j055306

Effect of Free-Stream Turbulence on Characteristics of Fluctuating Forces Acting on Two Square Prisms in Tandem Arrangement

Journal of Fluids Engineering ◽

10.1115/1.3243526 ◽

1988 ◽

Vol 110 (2) ◽

pp. 140-146 ◽

Cited By ~ 21

Author(s):

H. Sakamoto ◽

H. Haniu

Keyword(s):

Reynolds Number ◽

Strouhal Number ◽

Turbulence Intensity ◽

Vortex Shedding ◽

Free Stream ◽

Switching Frequency ◽

Tandem Arrangement ◽

Free Stream Turbulence ◽

Fluid Forces ◽

Bistable Flow

The effect of the addition of the turbulence intensity to the free stream on the characteristics of the bistable flow which takes place around two square prisms in tandem arrangement was studied experimentally at a Reynolds number of 3.32 × 104. A method of obtaining the fluid forces acting on two prisms in the bistable flow regimes where two flow patterns appear intermittently was introduced, and then the characteristics of the fluid forces, the Strouhal number, and the switching frequency of the switch phenomenon with the variation of the freestream turbulence intensity were investigated. Furthermore, the behavior of the fluid forces and the vortex shedding for other spacings between the two prisms were presented for the variation of the turbulence intensity.

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Phenomena of vortex shedding and flow interference of three cylinders in different equilateral arrangements

Journal of Fluid Mechanics ◽

10.1017/s0022112088002587 ◽

1988 ◽

Vol 196 ◽

pp. 1-26 ◽

Cited By ~ 45

Author(s):

K. Lam ◽

W. C. Cheung

Keyword(s):

Vortex Shedding ◽

Reynolds Numbers ◽

Circular Cylinders ◽

Injection Technique ◽

Spacing Ratio ◽

Vortex Shedding Frequency ◽

Shedding Frequency ◽

Visualization Experiments ◽

Flow Interference ◽

Bistable Flow

This paper describes how the flows around three equal circular cylinders arranged in an equilateral-triangular manner interact at different angles of incidence α and spacing ratios l/d. Some vortex-shedding-frequency data evaluated from flow visualization experiments conducted at Reynolds numbers of 2.1 × 103 and 3.5 × 103, based on the diameter of a single cylinder, using a dye -injection technique, are presented. In order to provide additional insight to the understanding of the flow structure around this particular cylinder array, some photographs indicating the typical flow patterns for various arrangements are also presented. The investigation indicates that the flows interact in a complex fashion for spacing ratios smaller than 2.29 and it also reveals that, at this range of spacing ratios and at α = 0°, bistable flow characteristic exists. Moreover, for l/d approximately smaller than 4.65 there always exists an angle at which the vortex shedding behind an upstream cylinder is suppressed by a nearest downstream cylinder. This angle is found not to remain constant but increases as the spacing ratio increases. For illustration and comparisons, some numerical results obtained from the application of the surface-vorticity method have also been presented.

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SHIFT IN VORTEX SHEDDING MODE FOR FLOWOVER STREAMWISE OSCILLATING CYLINDER UNDER CONSTANT CONDITIONS

10.1615/tfec2020.fnd.032029 ◽

2020 ◽

Author(s):

Ahmad Elhares ◽

Krishna Shah ◽

Yanbao Ma

Keyword(s):

Vortex Shedding ◽

Oscillating Cylinder

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Evolution of unstable system.

JOURNAL OF ADVANCES IN PHYSICS ◽

10.24297/jap.v9i3.1349 ◽

2015 ◽

Vol 9 (3) ◽

pp. 2487-2502 ◽

Cited By ~ 1

Author(s):

Igor V. Lebed

Keyword(s):

Reynolds Number ◽

Vortex Shedding ◽

Stokes Flow ◽

Stable Solution ◽

The State ◽

Unstable System ◽

Unstable Flow ◽

Unstable Solutions ◽

Vortex Shedding Modes ◽

Hydrodynamics Equations

Scenario of appearance and development of instability in problem of a flow around a solidÂ sphere at rest is discussed. The scenario was created by solutions to the multimomentÂ hydrodynamics equations, which were applied to investigate the unstable phenomena. TheseÂ solutions allow interpreting Stokes flow, periodic pulsations of the recirculating zone in the wakeÂ behind the sphere, the phenomenon of vortex shedding observed experimentally. In accordanceÂ with the scenario, system loses its stability when entropy outflow through surface confining theÂ system cannot be compensated by entropy produced within the system. The system does not findÂ a new stable position after losing its stability, that is, the system remains further unstable. AsÂ Reynolds number grows, one unstable flow regime is replaced by another. The replacement isÂ governed tendency of the system to discover fastest path to depart from the state of statisticalÂ equilibrium. This striving, however, does not lead the system to disintegration. Periodically,Â reverse solutions to the multimoment hydrodynamics equations change the nature of evolutionÂ and guide the unstable system in a highly unlikely direction. In case of unstable system, unlikelyÂ path meets the direction of approaching the state of statistical equilibrium. Such behavior of theÂ system contradicts the scenario created by solutions to the classic hydrodynamics equations.Â Unstable solutions to the classic hydrodynamics equations are not fairly prolonged along time toÂ interpret experiment. Stable solutions satisfactorily reproduce all observed stable medium states.Â As Reynolds number grows one stable solution is replaced by another. They are, however,Â incapable of reproducing any of unstable regimes recorded experimentally. In particular, stableÂ solutions to the classic hydrodynamics equations cannot put anything in correspondence to anyÂ of observed vortex shedding modes. In accordance with our interpretation, the reason for this isthe classic hydrodynamics equations themselves.

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