The Effect of Sound on Vortex Shedding From Single and Tandem Cylinders

2002 ◽  
Author(s):  
Joseph W. Hall ◽  
Samir Ziada ◽  
David S. Weaver
Keyword(s):  
Vortex Shedding ◽  
Sound Field ◽  
Open Circuit ◽  
Mean Flow ◽  
Number Range ◽  
Single Cylinder ◽  
Tandem Cylinders ◽  
Vortex Shedding Frequency ◽  
The Mean ◽  
Lock In

A single cylinder and two tandem cylinders configurations with longitudinal pitch ratios L/D = 1.75 and 2.5 were rigidly mounted in an open circuit windtunnel and a sound field was applied so that the acoustic particle velocity was normal to both the cylinder axis and the mean flow velocity. Tests were performed for a Reynolds number range of 5000 < ReD < 24000. The effect of sound on the vortex shedding was investigated by instrumenting the cylinders with pressure taps and hot-wire probes. These tests show that applied sound can entrain and shift the natural vortex shedding frequency to the frequency of excitation and produce nonlinearities in the wake. The lock-in envelope for the tandem cylinders is considerably larger than for the single cylinder. The lock-in range for the smaller tandem cylinder spacing (L/D = 1.75) was broader still than either the single cylinder, or the L/D = 2.5 tandem cylinder 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.

The Unsteady Lift on Bluff Cylindrical Bodies in Unsteady Flow

1982 ◽  
Vol 33 (3) ◽  
pp. 219-236 ◽  
Author(s):  
H. Stapountzis ◽  
J.M.R. Graham
Keyword(s):  
Vortex Shedding ◽  
Elliptic Cylinder ◽  
Reynolds Numbers ◽  
Bluff Bodies ◽  
Mean Flow ◽  
Vortex Shedding Frequency ◽  
The Mean ◽  
Shedding Frequency ◽  
Naca 0015 ◽  
Unsteady Lift

SummaryThe unsteady lift generated on a NACA 0015 aerofoil, a D cylinder (with the flat face down-stream) and an elliptic cylinder was measured when these bodies were exposed to a flow with a two-dimensional sinusoidal upwash at reduced frequencies 0.05 to 0.8. The mean flow Reynolds numbers were in the range 1.2 × 105 to 3 × 105. Unsteady thin aerofoil theory was used in an attempt to predict the unsteady lift on the bluff bodies, as well as the aerofoil section for fequencies in the low range below the vortex shedding frequency. The results were quite accurate for the aerofoil and the D cylinder, but the aerodynamic admittance predicted by this theory for the elliptic cylinder was significantly above that measured experimentally. The movement of the two free separation points was found to play an important role in the characteristic lift behaviour of the elliptic cylinder.

scholarly journals Investigation of passive control of the wake past a thick plate by stability and sensitivity analysis of experimental data

2017 ◽  
Vol 828 ◽  
pp. 753-778 ◽  
Author(s):  
S. Camarri ◽  
R. Trip ◽  
J. H. M. Fransson
Keyword(s):  
Experimental Data ◽  
Sensitivity Analysis ◽  
Vortex Shedding ◽  
Flow Model ◽  
Flow Fields ◽  
Mean Flow ◽  
Vortex Shedding Frequency ◽  
The Mean ◽  
Shedding Frequency ◽  
The Stability

In this paper we propose a strategy, entirely relying on available experimental data, to estimate the effect of a small control rod on the frequency of vortex shedding in the wake past a thick perforated plate. The considered values of the flow Reynolds number range between $Re\simeq 6.6\times 10^{3}$ and $Re=5.3\times 10^{4}$. By means of particle image velocimetry, an experimental database consisting of instantaneous flow fields is collected for different values of suction through the body surface. The strategy proposed here is based on classical stability and sensitivity analysis applied to mean flow fields and on the formulation of an original ad hoc model for the mean flow. The mean flow model is obtained by calibrating the closure of the Reynolds averaged Navier–Stokes equations on the basis of the available experimental data through an optimisation algorithm. As a result, it is shown that the predicted control map agrees reasonably well with the equivalent one measured experimentally. Moreover, it is shown that even when turbulence effects are neglected, the stability analysis applied to the mean flow fields provides a reasonable estimation of the vortex shedding frequency, confirming what is known in the literature and extending it up to $Re=5.3\times 10^{4}$. It is also shown that, when turbulence is taken into account in the stability analysis using the same closure that is calibrated for the corresponding mean flow model, the prediction of the vortex shedding frequency is systematically improved.

The Spanwise Dependence of Vortex-Shedding From Yawed Circular Cylinders

2009 ◽  
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° to α = 90°. The Reynolds number based upon 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° to 1.1D for α = 60°. The commonly used independence principle was shown to predict the vortex-shedding frequency reasonably well along the entire cylinder span for α > 70°, but did not work as well for α = 60°.

Sidewall finite-conductivity effects in confined turbulent thermal convection

2002 ◽  
Vol 473 ◽  
pp. 201-210 ◽  
Author(s):  
ROBERTO VERZICCO
Keyword(s):  
Boundary Conditions ◽  
Thermal Convection ◽  
Lateral Wall ◽  
Finite Conductivity ◽  
Mean Flow ◽  
Number Range ◽  
Additional Heat ◽  
Low Aspect Ratio ◽  
Temperature Boundary ◽  
The Mean

The effects of a sidewall with finite thermal conductivity on confined turbulent thermal convection has been investigated using direct numerical simulation. The study is motivated by the observation that the heat flowing through the lateral wall is not always negligible in the low-aspect-ratio cells of several recent experiments. The extra heat flux modifies the temperature boundary conditions of the flow and therefore the convective heat transfer. It has been found that, for usual sidewall thicknesses, the heat travelling from the hot to the cold plates directly through the sidewall is negligible owing to the additional heat exchanged at the lateral fluid/wall interface. In contrast, the modified temperature boundary conditions alter the mean flow yielding significant Nusselt number corrections which, in the low Rayleigh number range, can change the exponent of the Nu vs. Ra power law by 10%.

Scaling laws for pipe-flow turbulence

1975 ◽  
Vol 67 (2) ◽  
pp. 257-271 ◽  
Author(s):  
A. E. Perry ◽  
C. J. Abell
Keyword(s):  
Pipe Flow ◽  
Scaling Laws ◽  
Dynamic Calibration ◽  
Turbulence Structure ◽  
Mean Flow ◽  
Number Range ◽  
Static Calibration ◽  
Calibration Methods ◽  
The Mean ◽  
Flow Turbulence

Using hot-wire-anemometer dynamic-calibration methods, fully developed pipe-flow turbulence measurements have been taken in the Reynolds-number range 80 × 103 to 260 × 103. Comparisons are made with the results of previous workers, obtained using static-calibration methods. From the dynamic-calibration results, a consistent and systematic correlation for the distribution of turbulence quantities becomes evident, the resulting correlation scheme being similar to that which has previously been established for the mean flow. The correlations reported have been partly conjectured in the past by many workers but convincing experimental evidence has always been masked by the scatter in the results, no doubt caused by the difficulties associated with static-calibration methods, particularly the earlier ones. As for the mean flow, the turbulence intensity measurements appear to collapse to an inner and outer law with a region of overlap, from which deductions can be made using dimensional arguments. The long-suspected similarity of the turbulence structure and its consistency with the established mean-flow similarity appears to be confirmed by the measurements reported here.

Vortex Shedding Induced Dynamic Response of Marine Risers

1984 ◽  
Vol 106 (2) ◽  
pp. 214-221 ◽  
Author(s):  
F. Rajabi ◽  
M. F. Zedan ◽  
A. Mangiavacchi
Keyword(s):  
Dynamic Response ◽  
Vortex Shedding ◽  
Equation Of Motion ◽  
Continuous Beam ◽  
Regular Waves ◽  
Empirical Correlations ◽  
Fluid Resistance ◽  
Vortex Shedding Frequency ◽  
Shedding Frequency ◽  
Lock In

An analytical model to predict the dynamic response of a riser in regular waves or in current to vortex shedding-induced lift forces is described. The riser is treated as a continuous beam under tension. A modal superposition scheme is used to solve the linearized equation of motion in the frequency domain. The excitation lift force is represented by a harmonic function with a frequency equal to the dominant vortex shedding frequency. Empirical correlations are used to determine the lift coefficients and shedding frequencies along the riser. Lift amplification is considered at or near the “lock-in” conditions. The fluid resistance to riser oscillations is represented by a Morison’s equation-type expression.

Experimental Investigation of a Tandem Cylinder System With a Yawed Upstream Cylinder

2011 ◽  
Author(s):  
Stephen J. Wilkins ◽  
Joseph W. Hall
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Unsteady Flow ◽  
Surface Pressure ◽  
Vortex Shedding ◽  
Flow Direction ◽  
Pressure Fluctuations ◽  
Mean Flow ◽  
The Mean ◽  
Velocity Spectra

The unsteady flow field produced by a tandem cylinder system with the upstream cylinder yawed to the mean flow direction is investigated for upstream cylinder yaw angles from α = 60° to α = 90°. Multi-point fluctuating surface pressure and hotwire measurements were conducted at various spanwise positions on both the upstream and downstream cylinders. The results indicate that yawing the front cylinder to the mean flow direction causes the pressure and velocity spectra on the upstream and downstream cylinders to become more broadband than for a regular tandem cylinder system, and reduces the magnitude of the peak associated with the vortex-shedding. However, span-wise correlation and coherence measurements indicate that the vortex-shedding is still present and was being obscured by the enhanced three-dimensionality that the upstream yawed cylinder caused and was still present and correlated from front to back, at least for the larger yaw angles investigated. When the cylinder was yawed to α = 60°, the pressure fluctuations became extremely broadband and exhibited shorter spanwise correlation.

A Continuous Prediction Method for Fully Developed Laminar, Transitional, and Turbulent Flows in Pipes

1975 ◽  
Vol 42 (1) ◽  
pp. 51-54 ◽  
Author(s):  
N. W. Wilson ◽  
R. S. Azad
Keyword(s):  
Turbulent Flows ◽  
Flow Characteristics ◽  
Prediction Method ◽  
Reynolds Numbers ◽  
Mean Flow ◽  
Number Range ◽  
Circular Pipes ◽  
The Mean ◽  
Single Set ◽  
Good Agreement

A single set of equations is developed to predict the mean flow characteristics in long circular pipes operating at laminar, transitional, and turbulent Reynolds numbers. Generally good agreement is obtained with available data in the Reynolds number range 100 < Re < 500,000.

Wake-Induced Vibration (WIV) of Two Tandem Pre-Tensioned Flexible Cylinders

2013 ◽  
Author(s):  
Bijan Sanaati ◽  
Naomi Kato
Keyword(s):  
Amplitude Ratio ◽  
Cross Flow ◽  
Dynamic Responses ◽  
Flexible Cylinder ◽  
Number Range ◽  
Frequency Responses ◽  
Aspect Ratios ◽  
Tandem Cylinders ◽  
Low Mass ◽  
Lock In

It is believed that investigations on flow around pairs of cylinders can provide a better understanding of the interference effects than the cases involving larger numbers of cylinders. Studies that deal with the dynamic responses of multiple flexible cylinders with low mass ratios and high aspect ratios are few because of the complexities in the responses. In this paper, the effects of wake interference on the dynamic responses of two pre-tensioned flexible cylinders in tandem arrangement subjected to uniform cross-flow are investigated. The analysis results of the tandem cylinders are presented and compared with an isolated flexible cylinder. Two flexible cylinders of the same size, properties, and pretensions were tested at four different centre-to-centre separation distances, namely, 2.75, 5.5, 8.25 and 11 diameters. Reynolds number range is from 1400 to 20000 (subcritical regime). The aspect ratio of the cylinders is 162 (length over diameter). Mass ratio (cylinders mass over displaced water) is 1.17. The amplitude ratio of the CF vibration of the downstream cylinder, IL deflections of both cylinders, frequency responses in both CF and inline (IL) directions were analyzed. For all the examined separation distances, the downstream cylinder does not show build-up of upper branch (within the lock-in region of the classical VIV of the isolated cylinder). The initial distance between the tandem cylinders cannot remain constant. The distance decreases with reduced velocity because of the unequal IL deflection of tandem cylinders. From the CF frequency response of the lift (transverse) force of downstream cylinder, the highest vibration amplitude at all the separation distances occurs whenever their frequencies transitioned into second modal value. The frequency responses of the upstream cylinder cannot be greatly affected by the downstream cylinder even for small separations in contrast to the downstream cylinder.

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