The Effects of Roughness and Shear on Vortex Shedding Cell Lengths Behind a Circular Cylinder

1982 ◽  
Vol 104 (1) ◽  
pp. 72-80 ◽  
Author(s):  
D. M. Rooney ◽  
R. D. Peltzer
Keyword(s):  
Wind Tunnel ◽  
Vortex Shedding ◽  
Reynolds Numbers ◽  
Cell Length ◽  
Circular Cylinders ◽  
Average Cell ◽  
Wide Range ◽  
Shear Parameter ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

Circular cylinders of aspect ratio L/D=17 were tested in a wind tunnel under a wide range of spanwise upstream velocity shears. The correlation between upstream shear, characterized by a nondimensional shear parameter β, and the spanwise lengths of constant vortex shedding frequency was sought for both smooth and rough cylinders in transitional Reynolds numbers flows. Among the significant conclusions are that the spanwise range in shedding frequencies decreases with increasing roughness, the average constant shedding frequency cell length increases with increasing roughness for constant shear, and the average cell length decreases with increasing upstream shear for constant roughness.

Finite Aspect Ratio Effects on Vortex Shedding Behind Two Cylinders at Angles of Incidence

1995 ◽  
Vol 117 (2) ◽  
pp. 219-226 ◽  
Author(s):  
D. M. Rooney ◽  
J. Rodichok ◽  
K. Dolan
Keyword(s):  
Wind Tunnel ◽  
Aspect Ratio ◽  
Vortex Shedding ◽  
Reynolds Numbers ◽  
Tip Vortex ◽  
Circular Cylinders ◽  
Aspect Ratios ◽  
Present Aspect ◽  
Shedding Frequency ◽  
The Difference

Wind tunnel tests were undertaken at subcritical Reynolds numbers to determine the vortex shedding characteristics behind a pair of finite circular cylinders at distances from one to six diameters apart and at all angles to one another. In addition, individual finite cylinders with aspect ratios 0.67 ≤ L/D ≤ 11.33 were examined to determine the effect of aspect ratio on shedding frequency, and to measure the frequency of the tip vortex when it is present. Aspect ratio was found to be a significant factor in the difference between shedding frequencies of the two cylinders at oblique angles. It was also found that “lock-on” of the two frequencies occurred when longer aspect ratio cylinders were upstream of shorter ones, but not in the reverse case.

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

1988 ◽  
Vol 196 ◽  
pp. 1-26 ◽  
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.

Investigation of Wall Induced Modifications to Vortex Shedding From a Circular Cylinder

1982 ◽  
Vol 104 (4) ◽  
pp. 518-522 ◽  
Author(s):  
F. Angrilli ◽  
S. Bergamaschi ◽  
V. Cossalter
Keyword(s):  
Velocity Field ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Frequency Measurements ◽  
Geometrical Pattern ◽  
Cylinder Diameter ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

In this paper the influence of a wall on vortex shedding frequency, geometrical pattern, and velocity field are investigated. Frequency measurements were carried out with three circular cylinders at Reynolds numbers of 2860, 3820, and 7640. Mean and fluctuating velocities at several traverses were also measured at Re = 3820 both for an isolated cylinder and for an arrangement with a gap from the wall equal to one cylinder diameter. The modifications of the wake pattern are shown in several figures. It is also shown that the proximity of the wall induces a slight increase of vortex shedding frequency.

An Experimental Study on the Vertical Flow Past a Finite-Length Horizontal Cylinder at Low Reynolds Numbers

2014 ◽  
Vol 493 ◽  
pp. 68-73 ◽  
Author(s):  
Willy Stevanus ◽  
Yi Jiun Peter Lin
Keyword(s):  
Finite Length ◽  
Vortex Shedding ◽  
Vortex Formation ◽  
Reynolds Numbers ◽  
Horizontal Cylinder ◽  
Vortex Street ◽  
Vertical Flow ◽  
Low Reynolds Numbers ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

The research studies the characteristics of the vertical flow past a finite-length horizontal cylinder at low Reynolds numbers (ReD) from 250 to 1080. The experiments were performed in a vertical closed-loop water tunnel. Flow fields were observed by the particle tracer approach for flow visualization and measured by the Particle Image Velocimetry (P.I.V.) approach for velocity fields. The characteristics of vortex formation in the wake of the finite-length cylinder change at different regions from the tip to the base of it. Near the tip, a pair of vortices in the wake was observed and the size of the vortex increased as the observed section was away from the tip. Around a distance of 3 diameters of the cylinder from its tip, the vortex street in the wake was observed. The characteristics of vortex formation also change with increasing Reynolds numbers. At X/D = -3, a pair of vortices was observed in the wake for ReD = 250, but as the ReD increases the vortex street was observed at the same section. The vortex shedding frequency is analyzed by Fast Fourier Transform (FFT). Experimental results show that the downwash flow affects the vortex shedding frequency even to 5 diameters of the cylinder from its tip. The interaction between the downwash flow and the Von Kármán vortex street in the wake of the cylinder is presented in this paper.

Wind Tunnel Study of Vortex Shedding behind Cooling Tower Models

2014 ◽  
Vol 617 ◽  
pp. 280-284
Author(s):  
Petr Michálek ◽  
David Zacho
Keyword(s):  
Wind Tunnel ◽  
Vortex Shedding ◽  
Cooling Tower ◽  
Time Signal ◽  
Hot Wire ◽  
Model Surface ◽  
Surface Measurements ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency ◽  
Wind Tunnel Study

Wind tunnel measurements of vortex shedding behind cooling tower models were performed in VZLU. Two variants of cooling tower models were used, i.e. model with smooth wall outer surface and model with rough wall surface. Measurements were conducted using hot-wire anemometer. Time signal from the anemometer was transformed using Fast-Fourier routine into frequency spectrum. Measurements have shown significant differences between smooth and rough variant of model surface and dependency of vortex shedding frequency on Reynolds number.

Computational Determination of the Modified Vortex Shedding Frequency for a Rigid, Truncated, Wall-Mounted Cylinder in Cross Flow

2014 ◽  
Author(s):  
Aimie Faucett ◽  
Todd Harman ◽  
Tim Ameel
Keyword(s):  
Vortex Shedding ◽  
Cross Flow ◽  
Classical Case ◽  
Reynolds Numbers ◽  
Two Dimensional ◽  
End Effects ◽  
Dimensional Solution ◽  
Horseshoe Vortices ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency

Flow around a rigid, truncated, wall-mounted cylinder with an aspect ratio of 5 is examined computationally at various Reynolds numbers Re to determine how the end effects impact the vortex shedding frequency. The existence of the wall and free end cause a dampening of the classical shedding frequency found for a semi-infinite, two-dimensional cylinder, as horseshoe vortices along the wall and flow over the tip entrain into the shedding region. This effect was observed for Reynolds numbers in the range of 50 to 2000, and quantified by comparing the modified Strouhal numbers to the classical (two-dimensional) solution for Strouhal number as a function of Reynolds number. The range of transition was found to be 220 < Re < 300, versus 150 < Re < 300 for the classical case. Vortex shedding started at Re ≈ 100, significantly above Re = 50, where shedding starts for the two-dimensional case.

The Spanwise Dependence of Vortex-Shedding From Yawed Circular Cylinders

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
James D. Hogan ◽  
Joseph W. Hall
Keyword(s):  
Vortex Shedding ◽  
Flow Direction ◽  
Rapid Decrease ◽  
Circular Cylinders ◽  
Mean Flow ◽  
Independence Principle ◽  
Simultaneous Measurements ◽  
Vortex Shedding Frequency ◽  
The Mean ◽  
Shedding Frequency

Simultaneous measurements of the fluctuating wall pressure along the cylinder span were used to examine the spanwise characteristics of the vortex-shedding for yaw angles varying from α=60 deg to α=90 deg. The Reynolds number based on the diameter of the cylinder was 56,100. The results indicate that yawing the cylinder to the mean flow direction causes the vortex-shedding in the wake to become more disorderly. This disorder is initiated at the upstream end of the cylinder and results in a rapid decrease in correlation length, from 3.3D for α=90 deg to 1.1D for α=60 deg. The commonly used independence principle was shown to predict the vortex-shedding frequency reasonably well along the entire cylinder span for α>70 deg, but did not work as well for α=60 deg.

A Study on Vortex Shedding From Spheres in a Uniform Flow

1990 ◽  
Vol 112 (4) ◽  
pp. 386-392 ◽  
Author(s):  
H. Sakamoto ◽  
H. Haniu
Keyword(s):  
Reynolds Number ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Water Channel ◽  
Reynolds Numbers ◽  
Uniform Flow ◽  
Freestream Velocity ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency ◽  
Visualization Experiments

Vortex shedding from spheres at Reynolds numbers from 3 × 102 to 4 × 104 in a uniform flow was investigated experimentally. Standard hot-wire technique were used to measure the vortex shedding frequency from spheres in a low-speed wind tunnel. Flow-visualization experiments were carried out in a water channel. Important results from the investigation were that (i) the variation of the Strouhal number St (=fD/U0, U0: freestream velocity, D: diameter of the sphere, f: vortex shedding frequency) with the Reynolds number (= U0D/v, v: kinematic viscosity) can be classified into four regions, (ii) the Reynolds number at which the hairpinshaped vortices begin to change from laminar to turbulent vortices so that the wake structure behind the sphere is not shown clearly when a Reynolds number of about 800 is reached, and (vi) at Reynolds numbers ranging from 8X102 to 1.5X104, the higher and lower frequency modes of the Strouhal number coexist.

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