Stability of a circular cylinder oscillating in uniform flow or in a wake

1973 ◽  
Vol 61 (4) ◽  
pp. 769-784 ◽  
Author(s):  
Y. Tanida ◽  
A. Okajima ◽  
Y. Watanabe
Keyword(s):  
Circular Cylinder ◽  
Vortex Formation ◽  
Longitudinal Mode ◽  
Longitudinal Direction ◽  
Transverse Mode ◽  
Reynolds Numbers ◽  
Uniform Flow ◽  
Transverse Oscillation ◽  
Circular Cylinders ◽  
Drag Forces

The lift and drag forces were measured on both a single circular cylinder and tandem circular cylinders in uniform flow at Reynolds numbers from 40 to 104, to investigate the stability of an oscillating cylinder. A cylinder (the downstream one in the tandem case) was made to oscillate in either the transverse or longitudinal direction (perpendicular or parallel to the stream). In the case of a single cylinder, its oscillation causes the so-called synchronization in a frequency range around the Strouhal frequency (transverse mode) or double the Strouhal frequency (longitudinal mode). The aerodynamic damping for transverse oscillation becomes negative in the synchronization range. In the case of tandem cylinders, at low Reynolds numbers in the pure Kármán range synchronization was observed to occur only when the downstream cylinder oscillated inside the vortex-formation region of the upstream one, and at high (low subcritical) Reynolds numbers synchronization occurred irrespective of the cylinder spacing in either oscillating mode. In the tandem case, too, the transverse oscillation of the downstream cylinder becomes unstable in the range of synchronization.

A Model for High-Reynolds-Number Flow Past Rough-Walled Circular Cylinders

1977 ◽  
Vol 99 (3) ◽  
pp. 486-493 ◽  
Author(s):  
O. Gu¨ven ◽  
V. C. Patel ◽  
C. Farell
Keyword(s):  
Boundary Layer ◽  
Surface Roughness ◽  
Circular Cylinder ◽  
Turbulent Boundary Layer ◽  
Pressure Coefficient ◽  
Empirical Relation ◽  
Reynolds Numbers ◽  
Boundary Layer Separation ◽  
Circular Cylinders ◽  
Mean Flow

A simple analytical model for two-dimensional mean flow at very large Reynolds numbers around a circular cylinder with distributed roughness is presented and the results of the theory are compared with experiment. The theory uses the wake-source potential-flow model of Parkinson and Jandali together with an extension to the case of rough-walled circular cylinders of the Stratford-Townsend theory for turbulent boundary-layer separation. In addition, a semi-empirical relation between the base-pressure coefficient and the location of separation is used. Calculation of the boundary-layer development, needed as part of the theory, is accomplished using an integral method, taking into account the influence of surface roughness on the laminar boundary layer and transition as well as on the turbulent boundary layer. Good agreement with experiment is shown by the results of the theory. The significant effects of surface roughness on the mean-pressure distribution on a circular cylinder at large Reynolds numbers and the physical mechanisms giving rise to these effects are demonstrated by the model.

Three-dimensional wakes behind cylinders of square and circular cross-section: early and long-time dynamics

2019 ◽  
Vol 870 ◽  
pp. 419-432 ◽  
Author(s):  
G. Agbaglah ◽  
C. Mavriplis
Keyword(s):  
Circular Cylinder ◽  
Three Dimensional ◽  
Circular Cross Section ◽  
Early Time ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Square Cylinder ◽  
Saturation Regime ◽  
Time Dynamics ◽  
Significant Difference

The flow in the near wake of a square cylinder at Reynolds numbers of 205 and 225, corresponding to three-dimensional wake instability modes $A$ and $B$, respectively, and that of the square’s circumscribed circular cylinder are examined by using three-dimensional Navier–Stokes numerical simulations. At small times, prior to the streamwise vortex shedding, a self-similar velocity is observed in the wake and no significant difference is observed in the dynamics of the flows past the square and the circular cylinders. The exponential growth of the three-dimensional instability reaches a saturation regime during this early time for the considered Reynolds numbers. Vortical structures in the wake at long times and shedding frequencies are very close for the square and the circular cylinders. The flow separation on the forward top and bottom corners of the square cylinder have the effect of increasing its effective width, making it comparable with the diameter of the circumscribed circular cylinder. Thus, Floquet multipliers and modes of the associated three-dimensional instabilities are shown to be very close for the two cylinders when using the circumscribed circular cylinder as the basis for a characteristic length scale. Most importantly, the wavenumber with the maximum growth rate, for modes $A$ and $B$, is approximately identical for the two cylinders.

An experimental investigation of the oscillating lift and drag of a circular cylinder shedding turbulent vortices

1961 ◽  
Vol 11 (2) ◽  
pp. 244-256 ◽  
Author(s):  
J. H. Gerrard
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Cylinder Surface ◽  
Fluctuating Pressure ◽  
Order Of Magnitude ◽  
Lift And Drag

The oscillating lift and drag on circular cylinders are determined from measurements of the fluctuating pressure on the cylinder surface in the range of Reynolds number from 4 × 103 to just above 105.The magnitude of the r.m.s. lift coefficient has a maximum of about 0.8 at a Reynolds number of 7 × 104 and falls to about 0.01 at a Reynolds number of 4 × 103. The fluctuating component of the drag was determined for Reynolds numbers greater than 2 × 104 and was found to be an order of magnitude smaller than the lift.

Experimental Studies on Loads Acting on Two Piles of Side-by-Side Arrangements in the Uniform Flow

2012 ◽  
Vol 226-228 ◽  
pp. 1785-1788
Author(s):  
Zhao Qing Zhu ◽  
Guo Liang Dai
Keyword(s):  
Drag Coefficient ◽  
Flow Velocity ◽  
Experimental Studies ◽  
Reynolds Numbers ◽  
Uniform Flow ◽  
Drag Forces ◽  
Pile Diameter ◽  
Two Component ◽  
Balance Analysis ◽  
Different Diameters

Indoor model experiments were made to study drag loads on two piles of side-by-side arrangements in the uniform flow. Take three different velocities of the flow, three different diameters of piles and five different distances of two piles in the experiments to get the variations of loads. Drag forces were measured by a two-component balance. Analysis on experiment results shows that drag forces increase with the increase of the pile diameter, the increase of the flow velocity and the decrease of the distance of two piles. The drag coefficient CDunder different Reynolds numbers shows the same change law. The drag coefficient CDdecreases with the increase of the distance of two piles and has good coherence to the ratio of the distance of two piles to the pile diameter.

scholarly journals The Lift and Drag Forces on Tandem Circular Cylinders Oscillating in Uniform Flow

1974 ◽  
Vol 40 (331) ◽  
pp. 765-773
Author(s):  
Yasuyuki WATANABE ◽  
Atsushi OKAJIMA ◽  
Yosimiti TANIDA
Keyword(s):  
Uniform Flow ◽  
Circular Cylinders ◽  
Drag Forces ◽  
Lift And Drag

scholarly journals Rotary oscillation control of a cylinder wake

1991 ◽  
Vol 224 ◽  
pp. 77-90 ◽  
Author(s):  
P. T. Tokumaru ◽  
P. E. Dimotakis
Keyword(s):  
Flow Visualization ◽  
Free Stream ◽  
Reynolds Numbers ◽  
Uniform Flow ◽  
Circular Cylinders ◽  
Cylinder Wake ◽  
Oscillation Control ◽  
Displacement Thickness ◽  
Cylinder Drag

Exploratory experiments have been performed on circular cylinders executing forced rotary oscillations in a steady uniform flow. Flow visualization and wake profile measurements at moderate Reynolds numbers have shown that a considerable amount of control can be exerted over the structure of the wake by such means. In particular, a large increase, or decrease, in the resulting displacement thickness, estimated cylinder drag, and associated mixing with the free stream can be achieved, depending on the frequency and amplitude of oscillation.

Numerical Prediction of Flow Fields Around Circular Cylinders: Forced Motion and Dynamic Response Cases

2000 ◽  
Vol 122 (4) ◽  
pp. 703-714 ◽  
Author(s):  
S. Lu ◽  
O¨. F. Turan
Keyword(s):  
Circular Cylinder ◽  
Dynamic Response ◽  
Relative Phase ◽  
Stokes Equations ◽  
Cross Flow ◽  
Structural Equations ◽  
Transverse Oscillation ◽  
Circular Cylinders ◽  
Navier Stokes ◽  
Navier Stokes Equations

At Re=2000, the predicted flow field around a circular cylinder in forced transverse oscillation is verified with experimental results. For coupled torsional and transverse oscillation cases, the numerical results indicate that lock-in depends on the relative phase between torsional and translational oscillations. The dynamic response of an elastically mounted circular cylinder in cross flow, obtained by solving the structural equations simultaneously with the Navier-Stokes equations, is in reasonable agreement with experimental data. The dynamic response results indicate that the change of wake pattern from 2S to 2P with increased frequency ratio, is not always simultaneous with the change in the relative phase between lift force and cylinder displacement. [S0098-2202(00)02003-4]

Experiments on the flow past a circular cylinder at low Reynolds numbers

1959 ◽  
Vol 6 (4) ◽  
pp. 547-567 ◽  
Author(s):  
D. J. Tritton
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Experimental Evidence ◽  
Theoretical Calculations ◽  
Reynolds Numbers ◽  
Vortex Street ◽  
Circular Cylinders ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
Experimental Values

Part I describes measurements of the drag on circular cylinders, made by observing the bending of quartz fibres, in a stream with the Reynolds number range 0·5-100. Comparisons are made with other experimental values (which cover only the upper part of this range) and with the various theoretical calculations.Part II advances experimental evidence for there being a transition in the mode of the vortex street in the wake of a cylinder at a Reynolds number around 90. Investigations of the nature of this transition and the differences between the flows on either side of it are described. The interpretation that the change is between a vortex street originating in the wake and one originating in the immediate vicinity of the cylinder is suggested.

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