A Basic Research on the VIV Response of Rotating Circular Cylinder in Flow

2011 ◽  
Author(s):  
Chang-Kyu Rheem ◽  
Koichiro Kato
Keyword(s):  
Circular Cylinder ◽  
Natural Frequency ◽  
Vortex Shedding ◽  
Oscillation Amplitude ◽  
Water Channel ◽  
Basic Research ◽  
Rotation Frequency ◽  
Circular Cylinders ◽  
Discrete Vortex ◽  
Rotating Circular Cylinder

The characteristics of VIV response of rotating circular cylinders in flow had been investigated by both experiment and numerical simulation. In the experiment, the motions of a flexible circular cylinder pipe installed in a circulation water channel were measured. In simulation, a Discrete Vortex Method had been used to estimate hydrodynamic forces acting on a rigid circular cylinder. When a cylinder rotates in flow, a rotation frequency becomes important added to natural frequency and vortex shedding frequency. The deflection of a flexble pipe peaked when the frequency ratio of rotation frequency to natural frequency was between 1.0 and 1.5. This is similar to increment of oscillation amplitude by a resonance of natural vibration and vortex shedding. The peak oscillation frequency of a rotating circular cylinder in flow decreased with increase in rotation number. The main axis of cylinder oscillation turned in the rotation direction.

A Numerical Study of Vortex Shedding From One and Two Circular Cylinders

1981 ◽  
Vol 32 (1) ◽  
pp. 48-71 ◽  
Author(s):  
P.K. Stansby
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Potential Flow ◽  
Numerical Study ◽  
Circular Cylinders ◽  
Discrete Vortex ◽  
Formation Region ◽  
Flow Features ◽  
The Mean

SummaryA discrete-vortex representation of the wake of a circular cylinder, in which vortices are convected in a potential-flow calculation and maintain their identities unless they approach one another or a surface closely, predicts many of the unsteady flow features and is computationally more efficient than other schemes. The mean rate of shedding of vorticity is adjusted to be compatible with experiments at a high subcritical Reynolds number of 3 × 104 and the model gives reasonable predictions of separation, drag, lift, Strouhal number and vorticity loss in the formation region. The method is extended to accommodate a second cylinder and many of the surprising features which have been observed experimentally with two cylinders in a side-by-side arrangement are reproduced.

Forces on cylinders in viscous oscillatory flow at low Keulegan-Carpenter numbers

1985 ◽  
Vol 154 ◽  
pp. 337-356 ◽  
Author(s):  
P. W. Bearman ◽  
M. J. Downie ◽  
J. M. R. Graham ◽  
E. D. Obasaju
Keyword(s):  
Cross Section ◽  
Vortex Shedding ◽  
Water Channel ◽  
Inertial Force ◽  
Circular Cylinders ◽  
Discrete Vortex ◽  
Laminar Boundary Layers ◽  
Line Force ◽  
Theoretical Results ◽  
Displacement Effects

This paper presents a comparison between theory and experiment for the in-line forces on cylinders of general cross-section in planar oscillatory flows of small amplitude. The theoretical analysis evaluates corrections to the standard inviscid inertial force at low Keulegan-Carpenter numbers which arise from the presence of viscous laminar boundary layers and from the development of vortex shedding. The boundary-layer contribution due to both skin friction and displacement effects is calculated to first order in the Stokes parameter β−½. The contribution to the in-line force from separation and vortex shedding, for which the results presented only apply to sharp-edged bodies, is taken from previous work on vortex shedding from isolated edges using the discrete vortex modelling technique. The resulting force has components both in phase with the fluid acceleration (inertia) and in phase with the velocity (drag).The theoretical results are compared to measurements taken in a [xcup ]-tube water channel on a number of cylinders of different cross-section including circular cylinders and sharp-edged sections. The comparisons suggest that the theory is valid for Keulegan–Carpenter numbers below about 3 and for moderately high values of the β parameter.

Flows past a rotating circular cylinder by the discrete vortex method.

1989 ◽  
Vol 9 (34) ◽  
pp. 273-276
Author(s):  
Takeyoshi Kimura ◽  
Michihisa Tsutahara ◽  
Zhong-yi Wang ◽  
Hiroshi Ishii
Keyword(s):  
Circular Cylinder ◽  
Vortex Method ◽  
Discrete Vortex ◽  
Discrete Vortex Method ◽  
Rotating Circular Cylinder

Influence of slip on the flow past superhydrophobic circular cylinders

2011 ◽  
Vol 680 ◽  
pp. 459-476 ◽  
Author(s):  
PRANESH MURALIDHAR ◽  
NANGELIE FERRER ◽  
ROBERT DANIELLO ◽  
JONATHAN P. ROTHSTEIN
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Flow Direction ◽  
Superhydrophobic Surfaces ◽  
Separation Point ◽  
Circular Cylinders ◽  
Recirculation Region ◽  
Small Scale ◽  
Flow Past ◽  
Shedding Frequency

Superhydrophobic surfaces have been shown to produce significant drag reduction for both laminar and turbulent flows of water through large- and small-scale channels. In this paper, a series of experiments were performed which investigated the effect of superhydrophobic-induced slip on the flow past a circular cylinder. In these experiments, circular cylinders were coated with a series of superhydrophobic surfaces fabricated from polydimethylsiloxane with well-defined micron-sized patterns of surface roughness. The presence of the superhydrophobic surface was found to have a significant effect on the vortex shedding dynamics in the wake of the circular cylinder. When compared to a smooth, no-slip cylinder, cylinders coated with superhydrophobic surfaces were found to delay the onset of vortex shedding and increase the length of the recirculation region in the wake of the cylinder. For superhydrophobic surfaces with ridges aligned in the flow direction, the separation point was found to move further upstream towards the front stagnation point of the cylinder and the vortex shedding frequency was found to increase. For superhydrophobic surfaces with ridges running normal to the flow direction, the separation point and shedding frequency trends were reversed. Thus, in this paper we demonstrate that vortex shedding dynamics is very sensitive to changes of feature spacing, size and orientation along superhydrophobic surfaces.

Numerical investigation of wake flow regimes behind a high-speed rotating circular cylinder in steady flow

2019 ◽  
Vol 878 ◽  
pp. 875-906
Author(s):  
Adnan Munir ◽  
Ming Zhao ◽  
Helen Wu ◽  
Lin Lu
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
Vortex Shedding ◽  
Rotation Rate ◽  
High Speed ◽  
Three Dimensional ◽  
Flow Regimes ◽  
Reynolds Numbers ◽  
Wake Flow ◽  
Rotating Circular Cylinder

Flow around a high-speed rotating circular cylinder for $Re\leqslant 500$ is investigated numerically. The Reynolds number is defined as $UD/\unicode[STIX]{x1D708}$ with $U$, $D$ and $\unicode[STIX]{x1D708}$ being the free-stream flow velocity, the diameter of the cylinder and the kinematic viscosity of the fluid, respectively. The aim of this study is to investigate the effect of a high rotation rate on the wake flow for a range of Reynolds numbers. Simulations are performed for Reynolds numbers of 100, 150, 200, 250 and 500 and a wide range of rotation rates from 1.6 to 6 with an increment of 0.2. Rotation rate is the ratio of the rotational speed of the cylinder surface to the incoming fluid velocity. A systematic study is performed to investigate the effect of rotation rate on the flow transition to different flow regimes. It is found that there is a transition from a two-dimensional vortex shedding mode to no vortex shedding mode when the rotation rate is increased beyond a critical value for Reynolds numbers between 100 and 200. Further increase in rotation rate results in a transition to three-dimensional flow which is characterized by the presence of finger-shaped (FV) vortices that elongate in the wake of the cylinder and very weak ring-shaped vortices (RV) that wrap the surface of the cylinder. The no vortex shedding mode is not observed at Reynolds numbers greater than or equal to 250 since the flow remains three-dimensional. As the rotation rate is increased further, the occurrence frequency and size of the ring-shaped vortices increases and the flow is dominated by RVs. The RVs become bigger in size and the flow becomes chaotic with increasing rotation rate. A detailed analysis of the flow structures shows that the vortices always exist in pairs and the strength of separated shear layers increases with the increase of rotation rate. A map of flow regimes on a plane of Reynolds number and rotation rate is presented.

scholarly journals Control and Suppression of Vortex Shedding from a Slightly Rough Circular Cylinder by a Discrete Vortex Method

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4481 ◽  
Author(s):  
Marcos André de Oliveira ◽  
Paulo Guimarães de Moraes ◽  
Crystianne Lilian de Andrade ◽  
Alex Mendonça Bimbato ◽  
Luiz Antonio Alcântara Pereira
Keyword(s):  
Circular Cylinder ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Vortex Method ◽  
Control Technique ◽  
Saturation State ◽  
Discrete Vortex ◽  
Discrete Vortex Method ◽  
Moving Wall ◽  
History Of

A discrete vortex method is implemented with a hybrid control technique of vortex shedding to solve the problem of the two-dimensional flow past a slightly rough circular cylinder in the vicinity of a moving wall. In the present approach, the passive control technique is inspired on the fundamental principle of surface roughness, promoting modifications on the cylinder geometry to affect the vortex shedding formation. A relative roughness size of ε*/d* = 0.001 (ε* is the average roughness and d* is the outer cylinder diameter) is chosen for the test cases. On the other hand, the active control technique uses a wall plane, which runs at the same speed as the free stream velocity to contribute with external energy affecting the fluid flow. The gap-to-diameter varies in the range from h*/d* = 0.05 to 0.80 (h* is the gap between the moving wall and the cylinder bottom). A detailed account of the time history of pressure distributions, simultaneously investigated with the time evolution of forces, Strouhal number behavior, and boundary layer separation are reported at upper-subcritical Reynolds number flows of Re = 1.0 × 105. The saturation state of the numerical simulations is demonstrated through the analysis of the Strouhal number behavior obtained from temporal history of the aerodynamic loads. The present work provides an improvement in the prediction of Strouhal number than other studies no using roughness model. The aerodynamic characteristics of the cylinder, as well as the control of intermittence and complete interruption of von Kármán-type vortex shedding have been better clarified.

The Passive Control of Unsteady Flow Structure Downstream of a Circular Cylinder in Shallow Water

2013 ◽  
Author(s):  
Tahir Durhasan ◽  
Engin Pınar ◽  
Muhammed M. Aksoy ◽  
Göktürk M. Özkan ◽  
Hüseyin Akıllı ◽  
...  
Keyword(s):  
Circular Cylinder ◽  
Shallow Water ◽  
Flow Structure ◽  
Vortex Shedding ◽  
Passive Control ◽  
Outer Cylinder ◽  
Water Channel ◽  
Stream Velocity ◽  
Image Velocimetry ◽  
Perforated Cylinder

In the present study, it was aimed to suppress the vortex shedding occurred in the near wake of a circular cylinder (inner cylinder) by perforated cylinder (outer cylinder) in shallow water flow. The inner cylinder (Di) and outer cylinder (Do) have fixed diameters, such as Di = 50 mm and Do = 100 mm, respectively. The effect of porosity, β, was examined using four different porosity ratios, 0.3, 0.5, 0.6 and 0.8. In order to investigate the effect of arc angle of outer cylinder, α, four different arc angles, α = 360°, 180°, 150° and 120° were used. The experiments were implemented in a recirculating water channel using the particle image velocimetry, PIV technique. The depth-averaged free-stream velocity was kept constant as U∞ = 100 mm/s which corresponded to a Reynolds number of Re = 5000 based on the inner cylinder diameter. The results demonstrated that the suppression of vortex shedding is substantially achieved by perforated outer cylinder for arc angle of α = 360° at β = 0.6. Turbulence Kinetic Energy statistics show that porosity, β, is highly effective on the flow structure. In comparison with the values obtained from the case of the bare cylinder, at porosity β = 0.6, turbulence characteristics are reduced by %80. Also, the point, which the values of maximum TKE, shift to a farther downstream compared to the case of bare cylinder.

Beating of a circular cylinder mounted as an inverted pendulum

2008 ◽  
Vol 610 ◽  
pp. 217-247 ◽  
Author(s):  
A. VOORHEES ◽  
P. DONG ◽  
P. ATSAVAPRANEE ◽  
H. BENAROYA ◽  
T. WEI
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Inverted Pendulum ◽  
Three Dimensional ◽  
Detailed Examination ◽  
Circular Cylinders ◽  
Response Analysis ◽  
Amplitude Response ◽  
Number Range ◽  
Spatially Resolved

This paper contains temporally and spatially resolved flow visualization and DPIV measurements characterizing the frequency–amplitude response and three-dimensional vortex structure of a circular cylinder mounted like an inverted pendulum. Two circular cylinders were examined in this investigation. Both were 2.54 cm in diameter and ~140 cm long with low mass ratios, m* = 0.65 and 1.90, and mass–damping ratios, m*ζ = 0.038 and 0.103, respectively. Frequency–amplitude response analysis was done with the lighter cylinder while detailed wake structure visualization and measurements were done using the slightly higher-mass-ratio cylinder. Experiments were conducted over the Reynolds number range 1900≤Re≤6800 corresponding to a reduced velocity range of 3.7 ≤ U* ≤ 9.6. Detailed examination of the upper branch of the synchronization regime permitted, for the first time, the identification of short-time deviations in cylinder oscillation and vortex-shedding frequencies that give rise to beating behaviour. That is, while long-time averages of cylinder oscillation and vortex-shedding frequencies are identical, i.e. synchronized, it is shown that there is a slight mismatch between these frequencies over much shorter periods when the cylinder exhibits quasi-periodic beating. Data are also presented which show that vortex strength is also modulated from one cylinder oscillation to the next. Physical arguments are presented to explain both the origins of beating as well as why the quasi-periodicity of the beating envelopes becomes irregular; it is believed that this result may be generalized to a broader class of fluid–structure interactions. In addition, observations of strong vertical flows associated with the Kármán vortices developing 2–3 diameters downstream of the cylinder are presented. It is hypothesized that these three-dimensionalities result from both the inverted pendulum motion as well as free-surface effects.

Influence of Thermal Buoyancy on Vortex Shedding Behind a Rotating Circular Cylinder in Cross Flow at Subcritical Reynolds Numbers

2014 ◽  
Vol 136 (5) ◽  
Author(s):  
Dipankar Chatterjee ◽  
Chiranjit Sinha
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Thermal Instability ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
Forced Flow ◽  
Thermal Buoyancy ◽  
Thermal Fields ◽  
Rotating Circular Cylinder ◽  
Unbounded Medium

The vortex shedding (VS) behind stationary bluff obstacles in cross-flow can be initiated by imposing thermal instability at subcritical Reynolds numbers (Re). We demonstrate here that additional thermal instability is required to be imparted in the form of heating for destabilizing the flow around a rotating bluff obstacle. A two-dimensional numerical simulation is performed in this regard to investigate the influences of cross buoyancy on the VS process behind a heated and rotating circular cylinder at subcritical Re. The flow is considered in an unbounded medium. The range of Re is chosen to be 5–45 with a dimensionless rotational speed (Ω) ranging between 0 and 4. At this subcritical range of Reynolds number the flow and thermal fields are found to be steady without the superimposed thermal buoyancy (i.e., for pure forced flow). However, as the buoyancy parameter (Richardson number, Ri) increases flow becomes unstable and subsequently, at some critical value of Ri, periodic VS is observed to characterize the flow and thermal fields. The rotation of the cylinder is found to have a stabilizing effect and as Ω increases more heating is observed to be required to destabilize the flow.

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