Numerical Simulation of Vortex-Induced Vibration of Two Rigidly Connected Cylinders in Side-by-Side and Tandem Arrangements Using RANS Model

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Ming Zhao ◽  
Joshua M. Murphy ◽  
Kenny Kwok
Keyword(s):  
Vortex Shedding ◽  
Flow Direction ◽  
Response Amplitude ◽  
Maximum Response ◽  
Circular Cylinders ◽  
Tandem Arrangement ◽  
Vortex Induced Vibration ◽  
Single Cylinder ◽  
Gap Ratio ◽  
G Ratio

Vortex-induced vibration (VIV) of two rigidly connected circular cylinders in side-by-side and tandem arrangements in the cross-flow direction was investigated using two-dimensional (2D) numerical simulations. The 2D Reynolds-Averaged Navier–Stokes (RANS) equations were solved for the flow, and the equation of the motion was solved for the response of the cylinders. Simulations were conducted for a constant mass ratio of 2.5, gap ratios G (ratio of the gap between the cylinders to the cylinder diameter) in the range of 0.5 to 3, and reduced velocities in the range of 1 to 30. The effects of the gap ratio on the response of the cylinders were analyzed extensively. The maximum response amplitude in the lock-in regime was found to occur at G = 0.5 in the side-by-side arrangement, which is about twice that of a single cylinder. In the side-by-side arrangement, the response regime of the cylinders for gap ratios of 1.5, 2, 2.5, and 3 is much narrower than that of a single cylinder, because the vortex shedding from the two cylinders is in an out-of-phase pattern at large reduced velocities. In the tandem arrangement, the maximum response amplitude of the cylinders is greater than that of a single cylinder for all the calculated gap ratios. For the gap ratio of 0.5 in the tandem arrangement, the vortex shedding frequency from the upstream cylinder was not observed in the vibration at large reduced velocities, and the response is galloping.

Two-dimensional numerical study of vortex shedding regimes of oscillatory flow past two circular cylinders in side-by-side and tandem arrangements at low Reynolds numbers

2014 ◽  
Vol 751 ◽  
pp. 1-37 ◽  
Author(s):  
Ming Zhao ◽  
Liang Cheng
Keyword(s):  
Vortex Shedding ◽  
Oscillatory Flow ◽  
Flow Regimes ◽  
Reynolds Numbers ◽  
The Other ◽  
Circular Cylinders ◽  
Two Dimensional ◽  
Low Reynolds Numbers ◽  
Single Cylinder ◽  
Gap Ratio

AbstractOscillatory flow past two circular cylinders in side-by-side and tandem arrangements at low Reynolds numbers is simulated numerically by solving the two-dimensional Navier–Stokes (NS) equations using a finite-element method (FEM). The aim of this study is to identify the flow regimes of the two-cylinder system at different gap arrangements and Keulegan–Carpenter numbers (KC). Simulations are conducted at seven gap ratios $\def \xmlpi #1{}\def \mathsfbi #1{\boldsymbol {\mathsf {#1}}}\let \le =\leqslant \let \leq =\leqslant \let \ge =\geqslant \let \geq =\geqslant \def \Pr {\mathit {Pr}}\def \Fr {\mathit {Fr}}\def \Rey {\mathit {Re}}G$ ($G=L/D$ where $L$ is the cylinder-to-cylinder gap and $D$ the diameter of a cylinder) of 0.5, 1, 1.5, 2, 3, 4 and 5 and KC ranging from 1 to 12 with an interval of 0.25. The flow regimes that have been identified for oscillatory flow around a single cylinder are also observed in the two-cylinder system but with different flow patterns due to the interactions between the two cylinders. In the side-by-side arrangement, the vortex shedding from the gap between the two cylinders dominates when the gap ratio is small, resulting in the gap vortex shedding (GVS) regime, which is different from any of the flow regimes identified for a single cylinder. For intermediate gap ratios of 1.5 and 2 in the side-by-side arrangement, the vortex shedding mode from one side of each cylinder is not necessarily the same as that from the other side, forming a so-called combined flow regime. When the gap ratio between the two cylinders is sufficiently large, the vortex shedding from each cylinder is similar to that of a single cylinder. In the tandem arrangement, when the gap between the two cylinders is very small, the flow regimes are similar to that of a single cylinder. For large gap ratios in the tandem arrangement, the vortex shedding flows from the gap side of the two cylinders interact and those from the outer sides of the cylinders are less affected by the existence of the other cylinder and similar to that of a single cylinder. Strong interaction between the vortex shedding flows from the two cylinders makes the flow very irregular at large KC values for both side-by-side and tandem arrangements.

Effect of Upstream Cylinder’s Oscillation Frequency on Downstream Cylinder’s Vortex Induced Vibration

2016 ◽  
Author(s):  
M. Mobassher Tofa ◽  
Adi Maimun ◽  
Yasser M. Ahmed
Keyword(s):  
Natural Frequency ◽  
Oscillation Frequency ◽  
Flow Direction ◽  
Cross Flow ◽  
Clean Energy ◽  
Mass Ratio ◽  
Flow Induced Vibration ◽  
Tandem Arrangement ◽  
Vortex Induced Vibration ◽  
Single Cylinder

Vortex induced vibration or widely known as VIV, is a very complex hydrodynamic phenomenon. There are relatively very few experimental and numerical references for oscillating pair of cylinders because of the early assumption that the interference between the two cylinders is weak and thus each of the cylinders may have the same behavior as found in the case of a single cylinder, but recent researches showed this assumption was not true. For tandem arrangement, several parameters govern the nature of VIV of downstream cylinders, such as spacing, upstream cylinders VIV amplitude etc. The nature of downstream cylinders response isn’t same as classical VIV or WIV (wake induced vibration). Oscillation frequency of a cylinder subjected to flow induced vibration is one of the important characteristics Oscillation frequency is highly dependent on natural frequency of the cylinder. By changing spring stiffness or mass ratio, natural frequency can be altered. The aim of this study is to investigate the effect of upstream cylinder’s oscillation frequency on the vibration of downstream cylinder. Numerical simulations have been conducted to understand the nature of vortex induced vibration (VIV) of a pair cylinder in tandem arrangement at high Reynolds numbers. Cylinders were subjected to uniform flows in sub-critical flow regime and have been allowed to oscillate in cross flow direction only. The spacing between the upstream and downstream cylinders was four times of the cylinder diameter. The oscillation frequency of the upstream cylinder has been altered by varying the mass ratio of the upstream cylinder. It was found that for same Reynolds number, downstream cylinder’s VIV amplitude is increased quite significantly if the upstream cylinder oscillates relatively slowly. The shear stress transport detached eddy turbulence model has been used for simulating the turbulent flow around the two cylinders. An advanced mesh movement known as “mesh morphing” model was employed to lessen the requirement for re-meshing which help to increase the accuracy of the prediction. Calculation of accurate results due to large domain deformations was achieved by re-positioning existing mesh points. The numerical results of a single cylinder subjected to one degree of freedom (1DOF) vibration have been compared with the available experimental results to validate the present study. The study is important in terms of designing VIVACE (Vortex Induced Vibration for Aquatic Clean Energy) converter for low speed current. In recent past, multiple cylinders have been used for VIVACE converter. So, the study of VIV of two equal-diameter cylinders in tandem arrangement at low current speed is very significant.

Vortex Shedding with Fluid Mechanics from Two Cylinders of Different Diameters in a Tandem Arrangement

2014 ◽  
Vol 886 ◽  
pp. 436-439
Author(s):  
Yong Tao Wang ◽  
Zhong Min Yan ◽  
Hui Min Wang
Keyword(s):  
Reynolds Number ◽  
Fluid Mechanics ◽  
Vortex Shedding ◽  
Diameter Ratio ◽  
Circular Cylinders ◽  
Tandem Arrangement ◽  
Gap Ratio ◽  
Different Diameters ◽  
Upstream Control ◽  
Control Cylinder

The vortex shedding from two circular cylinders of different diameters in a tandem arrangement is numerically investigated at a Reynolds number of 100 and 150. The studied Reynolds number based on the diameter of the downstream main cylinder. The diameter of the downstream main cylinder was kept constant, and the diameter ratio between the upstream control cylinder and the downstream one was varied from 0.1 to 1.0. The gap between the control cylinder and the main cylinder ranged from 0.1 to 4.0 times the diameter of the main cylinder. It is concluded that the gap ratio and the diameter ratio between the two cylinders have important effects on vortex shedding from two cylinders of different diameters in a tandem arrangement.

scholarly journals Experimental investigation on coupled cross-flow and in-line vortex-induced vibration responses of two staggered circular cylinders

2020 ◽  
pp. 147509022090747
Author(s):  
Cheng Zhang ◽  
Zhuang Kang ◽  
Yeping Xiong ◽  
Shangmao Ai ◽  
Gang Ma
Keyword(s):  
Model Test ◽  
Flow Direction ◽  
Cross Flow ◽  
Circular Cylinders ◽  
Amplitude Curve ◽  
Vortex Induced Vibration ◽  
Double Peaks ◽  
Gap Ratio ◽  
Vibration Responses ◽  
The Cross

In order to better understand the vortex-induced vibration mechanism of multiple cylinders, this article takes a relatively simple case of two staggered circular cylinders as the embarkation point and investigates their vortex-induced vibration characteristics by model test. The experimental Reynolds number ranges from 22,000 to 88,000. The in-line gap L is set as 3.0 D, 3.6 D, 4.2 D and 5.5 D in turn, and the cross-flow gap T is set as 0.7 D, 1.1 D, 1.5 D, 1.9 D, 2.3 D and 2.7 D, respectively. By measuring the vibrating response in model test, the response differences between the two staggered cylinders and the isolated cylinder and the effects of the gaps are discussed. The results indicate that the variation trend of response of the upstream cylinder with reduced velocity is basically similar to that of the isolated cylinder. However, the downstream cylinder shows some great differences. When the in-line gap ratio L/ D is 3.6, the cross-flow amplitude curve of downstream cylinder changes from “single peak” to “double peaks” with the increase in cross-flow gap ratio T/ D, and in-line amplitude curve even shows four different kinds of forms. When L/ D is increasing, maximum amplitudes of the downstream cylinder in two directions also show an increasing trend, and the wake galloping phenomenon even appears in some conditions. Generally, the case of staggered cylinders is a generalized combination of two circular cylinders in tandem and side-by-side arrangements, and this article has extended the research scope of the double-cylinder vortex-induced vibration to arbitrary flow direction.

In-Flow Oscillation of Circular Cylinders in Cross-Flow

2007 ◽  
Author(s):  
Tomomichi Nakamura ◽  
Hiroshi Haruguchi ◽  
Hiroyuki Nakajima ◽  
Toyohiro Sawada ◽  
Kozo Sugiyama
Keyword(s):  
High Speed ◽  
Flow Direction ◽  
Vortex Motion ◽  
Cross Flow ◽  
Video Camera ◽  
Circular Cylinders ◽  
Flow Oscillation ◽  
Single Cylinder ◽  
Digital Video Camera ◽  
Flow Oscillations

The importance of the in-flow oscillation of a single cylinder in cross-flow has been highlighted since an accident in a FBR-type reactor. In-flow oscillations have also been observed in tube arrays. This report is an experimental study on this phenomenon using totally nine cylinders in a water tunnel. Six cases, one single cylinder, two & three cylinders in parallel & in tandem, and a nine cylinder bundle, are examined. Every cylinder can move only in in-flow direction. The motion of cylinders is measured by the strain gages and by a high-speed digital video camera. The results are compared with the visualized vortex motion.

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.

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.

Vortex-Induced Vibration of Two Side-by-Side Cylinders With a Small Gap in Uniform Flow

2017 ◽  
Author(s):  
Adnan Munir ◽  
Ming Zhao ◽  
Helen Wu
Keyword(s):  
Stokes Equations ◽  
Flow Direction ◽  
Three Dimensional ◽  
Cross Flow ◽  
Circular Cylinders ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Gap Ratio ◽  
Vortex Induced Vibrations ◽  
Lock In

Vortex-induced vibrations of two elastically mounted and rigidly coupled circular cylinders in side-by-side arrangement in steady flow are investigated numerically. The vibration of the cylinders is limited to the cross-flow direction only. The three-dimensional Navier-Stokes equations are solved using the Petrov-Galerkin Finite element method and the equation of motion is solved using the fourth order Runge Kutta method. It is well known that when the gap between two stationary side-by-side cylinders is very small, the flow between the two cylinders is biased towards one cylinder and the lift force on each cylinder is significantly smaller than that of an isolated single cylinder. The aim of this study is to investigate the effect of a small gap ratio of 0.5 between the two cylinders on the lock-in regime and the amplitude of the vibration of two side-by-side cylinders in a fluid flow. Simulations are carried out for a constant mass ratio of 2, a constant Reynolds number of 1000 and a range of reduced velocities. It is found that in the lock-in range of the reduced velocity, the two cylinders vibrate about their balance position with high amplitudes. Outside the lock-in regime the flow from the gap becomes biased towards one cylinder, which is similar to that from the gap between stationary cylinders.

Vortex-Induced Vibration Experiment Research of Two Cylinders in Tandem Arrangement

2013 ◽  
Author(s):  
Zhuang Kang ◽  
Weixing Liu ◽  
Wei Qin
Keyword(s):  
Degrees Of Freedom ◽  
Flow Direction ◽  
Cross Flow ◽  
Near Wake ◽  
Tandem Arrangement ◽  
Vortex Induced Vibration ◽  
Wake Interference ◽  
Vibration Experiment ◽  
Low Mass ◽  
Far Wake

The vortex-induced vibration of tandem arrangement of two cylinders compared with the single cylinder is more complicated, The double cylinder arranged in tandem, which is free to move in two degrees of freedom respectively, and which has low mass and damping. The present study shows that a critical centre-to-centre spacing can be used to distinguish the far and near wake interference. The streams in this test were uniform flow, ranging from 0.2m/s to 0.8m/s with the interval of 0.1m/s. The Re numbers are ranging from 22000 to 88000. The mass ratio of cylinder is low. For far wake interference, the downstream cylinder shows large amplitudes of response, therefore the wake induced vibration (WIV) is found. For near wake interference, both the upstream cylinder and downstream cylinder are exposed to an evident phenomenon of VIV, but the amplitude of upstream and downstream are less than that of single cylinders in cross-flow direction and in-line direction. We found the critical spacing to be 3.4 to 4.9.

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