Vortex-induced vibrations of a circular cylinder at low Reynolds numbers

2007 ◽  
Vol 594 ◽  
pp. 463-491 ◽  
Author(s):  
T. K. PRASANTH ◽  
S. MITTAL
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Free Vibrations ◽  
Forced Vibrations ◽  
Two Dimensions ◽  
Element Formulation ◽  
Transverse Displacement ◽  
Mean Flow ◽  
Phase Jump ◽  
Vortex Induced Vibrations

Results are presented for a numerical simulation of vortex-induced vibrations of a circular cylinder of low non-dimensional mass (m* = 10) in the laminar flow regime (60 < Re < 200). The natural structural frequency of the oscillator, fN, matches the vortex shedding frequency for a stationary cylinder at Re = 100. This corresponds to fND2/ν = 16.6, where D is the diameter of the cylinder and ν the coefficient of viscosity of the fluid. A stabilized space–time finite element formulation is utilized to solve the incompressible flow equations in primitive variables form in two dimensions. Unlike at high Re, where the cylinder response is known to be associated with three branches, at low Re only two branches are identified: ‘initial’ and ‘lower’. For a blockage of 2.5% and less the onset of synchronization, in the lower Re range, is accompanied by an intermittent switching between two modes with vortex shedding occurring at different frequencies. With higher blockage the jump from the initial to lower branch is hysteretic. Results from free vibrations are compared to the data from experiments for forced vibrations reported earlier. Excellent agreement is observed for the critical amplitude required for the onset of synchronization. The comparison brings out the possibility of hysteresis in forced vibrations. The phase difference between the lift force and transverse displacement shows a jump of almost 180° at, approximately, the middle of the synchronization region. This jump is not hysteretic and it is not associated with any radical change in the vortex shedding pattern. Instead, it is caused by changes in the location and value of the maximum suction on the lower and upper surface of the cylinder. This is observed clearly by comparing the time-averaged flow for a vibrating cylinder for different Re. While the mean flow for Re beyond the phase jump is similar to that for a stationary cylinder, it is associated with a pair of counter-rotating vortices in the near wake for Re prior to the phase jump. The phase jump appears to be one of the mechanisms of the oscillator to self-limit its vibration amplitude.

Vortex-induced vibrations of a long flexible circular cylinder

1993 ◽  
Vol 250 ◽  
pp. 481-508 ◽  
Author(s):  
D. Brika ◽  
A. Laneville
Keyword(s):  
Circular Cylinder ◽  
Flow Velocity ◽  
Vortex Shedding ◽  
Abrupt Change ◽  
Velocity Range ◽  
End Effects ◽  
Synchronization Region ◽  
Vortex Induced Vibrations ◽  
Set Up ◽  
Vortex Shedding Modes

In an experimental study of the vortex-induced oscillations of a long flexible circular cylinder, the observed stationary amplitudes describe an hysteresis loop partially different from earlier studies. Each branch of the loop is associated with a vortex shedding mode and, as a jump from one branch to the other occurs, the phase difference between the cylinder displacement and the vortex shedding undergoes an abrupt change. The critical flow velocities at which the jump occurs concur with the flow visualization observations of Williamson & Roshko (1988) on the vortex shedding modes near the fundamental synchronization region. Impulsive regimes, obtained at a given flow velocity with the cylinder initially at rest or pre-excited, and progressive regimes resulting from a variation of the flow velocity, are examined. The occurrence of bifurcations is detected for a flow velocity range in the case of the impulsive regimes. The coordinates of the bifurcations define a boundary between two vortex shedding modes, a boundary that verifies the critical curve obtained by Williamson & Roshko (1988). The experimental set-up of this study simulates half the wavelength of a vibrating cable, eliminates the end effects present in oscillating rigid cylinder set-up and has one of the lowest damping ratios reported for the study of this phenomenon.

scholarly journals The Effect of Slat Opening on Vortex Shedding Behind a Circular Cylinder

2019 ◽  
Vol 8 (4) ◽  
pp. 6879-6885
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Governing Equation ◽  
Vortex Shedding ◽  
Vortex Formation ◽  
Bluff Bodies ◽  
Vortex Induced Vibrations ◽  
Better Than ◽  
Laminar Model

Add-on devices are widely used as one of the means of suppressing vortex induced vibrations from bluff bodies. The present study numerically investigates flow over a circular cylinder attached by an axial slat. The axial slat were of uniform and non-uniform openings of 67% and 44% porosity. The governing equation was solved using viscous-laminar model at Reynolds number, Re=300. It was found that the presence of the axial slats significantly suppressed vortex shedding behind the circular cylinder. The non-uniform slats showed longer vortex formation length with lower drag, in comparison to that of the uniform slats. In addition, the slats with 67% porosity of both uniform and non-uniform openings suppressed vortex better than that of 44% porosity slats, indicated by the longer vortex formation length and weaker intensity of vortices.

Vortex-Shedding From Various Yawed Tandem Circular Cylinder Arrangements

2012 ◽  
Author(s):  
Stephen J. Wilkins ◽  
Joseph W. Hall
Keyword(s):  
Experimental Investigation ◽  
Circular Cylinder ◽  
Flow Field ◽  
Vortex Shedding ◽  
Flow Direction ◽  
Pressure Fluctuations ◽  
Cylinder Wall ◽  
Pressure Measurements ◽  
Mean Flow ◽  
The Mean

The struts of a landing gear can be modeled as a tandem cylinder system where one cylinder is yawed to the mean flow direction. The current experimental investigation will examine the effect that yawing either the front or rear cylinder will have on the pressure fluctuations and associated unsteady flow field. This will be accomplished using 24 simultaneous unsteady wall pressure measurements on the cylinder wall. Two yaw angles will be examined here, α = 80° and α = 60°, for both the yawed upstream and yawed downstream cases.

Numerical simulation of the effect of wave form and sudden transverse displacement on vortex shedding from a circular cylinder

1997 ◽  
Author(s):  
J. Meneghini ◽  
Cesareo Siqueira ◽  
P. Bearman ◽  
J. Meneghini ◽  
Cesareo Siqueira ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Wave Form ◽  
Transverse Displacement

Response Analysis of a Circular Cylinder Undergoing Vortex Induced Vibrations Along Two Degrees of Freedom in the Presence of Noise

2017 ◽  
Author(s):  
M. S. Aswathy ◽  
Sunetra Sarkar
Keyword(s):  
Circular Cylinder ◽  
Degrees Of Freedom ◽  
Nonlinear Dynamical System ◽  
Real Life ◽  
Stochastic Modelling ◽  
Response Analysis ◽  
Mean Flow ◽  
Time Step ◽  
Two Degrees Of Freedom ◽  
Vortex Induced Vibrations

In this study, we perform uncertainty quantification of a nonlinear dynamical system consisting of a circular cylinder undergoing free vibrations with two degrees-of-freedom in the presence of a fluctuating flow-field. Most of the studies in Vortex Induced Vibrations till now are conducted in a deterministic environment. Real life situations involving VIV are subjected to high amount of uncertainties, with the main culprit being the randomness in the incoming flow. Studies involving modelling of the flow with a prescribed set of parameters, represents only an idealistic situation and hence is not sufficient for a complete understanding of the associated dynamics. In this context, we make an attempt to characterise the flow by doing a stochastic modelling on the same. In the current study, we have mathematically modelled the noise through a uniform distribution. These fluctuations are superimposed on a mean flow at every time step. We use a Duffing Van der Pol combined system to model the structure and flow oscillators. It is observed that stochastic modelling brings noticeable changes in the structural responses both quantitatively and qualitatively. The influence of the fluctuations on both the transverse and inline oscillations have been studied. One of the most important changes in the response of the structure is in its amplitude. Noise amplifies the maximum amplitude attained both for transverse and inline oscillations. Further, additional qualitative types of responses are visible in the presence of noise which were absent in the deterministic environment. One such behaviour the ‘intermittent’ response which occurs during the transition from higher to lower amplitudes in the lock-in region. Intermittency is observed both for transverse and inline oscillations. It has been seen that the system undergoes stochastic Phenomenological bifurcations, which have been characterised by the probability density functions of both the transverse and inline responses.

scholarly journals Vortex Shedding from a Circular Cylinder with Spiral Fin

2008 ◽  
Vol 3 (6) ◽  
pp. 787-795 ◽  
Author(s):  
Hiromitsu HAMAKAWA ◽  
Keisuke NAKASHIMA ◽  
Tomohiro KUDO ◽  
Eiichi NISHIDA ◽  
Tohru FUKANO
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding

Nonlinear Free and Forced Vibrations of Symmetric Laminated Panels

2011 ◽  
Vol 471-472 ◽  
pp. 616-621 ◽  
Author(s):  
Alireza Shooshtari ◽  
Soheil Razavi ◽  
Hadi Ghashochi Bargh ◽  
Mohammad Homayoun Sadr-Lahidjani
Keyword(s):  
Perturbation Method ◽  
External Force ◽  
Laminated Composite ◽  
Composite Plates ◽  
Forced Vibrations ◽  
Numerical Results ◽  
Transverse Displacement ◽  
Laminated Composite Plates ◽  
Free And Forced Vibrations ◽  
Laminated Panels

In this paper, free and forced vibrations of symmetric laminated composite plates are studied analytically by using a perturbation method where the analytical results for transverse displacement are compared with the numerical results. The external force is taken to be harmonic in time and having uniform amplitude.

Vortex shedding from a circular cylinder in moderate-Reynolds-number shear flow

1980 ◽  
Vol 101 (4) ◽  
pp. 721-735 ◽  
Author(s):  
Masaru Kiya ◽  
Hisataka Tamura ◽  
Mikio Arie
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Shear Flow ◽  
Vortex Shedding ◽  
Transverse Velocity ◽  
Number Range ◽  
Uniform Shear ◽  
Reynolds Number Range ◽  
Moderate Reynolds Number ◽  
Shear Parameter

The frequency of vortex shedding from a circular cylinder in a uniform shear flow and the flow patterns around it were experimentally investigated. The Reynolds number Re, which was defined in terms of the cylinder diameter and the approaching velocity at its centre, ranged from 35 to 1500. The shear parameter, which is the transverse velocity gradient of the shear flow non-dimensionalized by the above two quantities, was varied from 0 to 0·25. The critical Reynolds number beyond which vortex shedding from the cylinder occurred was found to be higher than that for a uniform stream and increased approximately linearly with increasing shear parameter when it was larger than about 0·06. In the Reynolds-number range 43 < Re < 220, the vortex shedding disappeared for sufficiently large shear parameters. Moreover, in the Reynolds-number range 100 < Re < 1000, the Strouhal number increased as the shear parameter increased beyond about 0·1.

scholarly journals Interaction between mean flow and turbulence in two dimensions

2016 ◽  
Vol 472 (2191) ◽  
pp. 20160287 ◽  
Author(s):  
Gregory Falkovich
Keyword(s):  
Short Note ◽  
Two Dimensions ◽  
Three Dimensions ◽  
Mean Flow ◽  
Turbulence Statistics ◽  
Planar Domains ◽  
Developed Turbulence ◽  
Aspect Ratios ◽  
Simple Geometry ◽  
Turbulent Cascade

This short note is written to call attention to an analytic approach to the interaction of developed turbulence with mean flows of simple geometry (jets and vortices). It is instructive to compare cases in two and three dimensions and see why the former are solvable and the latter are not (yet). We present the analytical solutions for two-dimensional mean flows generated by an inverse turbulent cascade on a sphere and in planar domains of different aspect ratios. These solutions are obtained in the limit of small friction when the flow is strong while turbulence can be considered weak and treated perturbatively. I then discuss when these simple solutions can be realized and when more complicated flows may appear instead. The next step of describing turbulence statistics inside a flow and directions of possible future progress are briefly discussed at the end.

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