scholarly journals Research on Flow-Induced Vibration and Energy Harvesting of Three Circular Cylinders with Roughness Strips in Tandem

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2977 ◽  
Author(s):  
Lin Ding ◽  
Qunfeng Zou ◽  
Li Zhang ◽  
Haibo Wang
Keyword(s):  
Reynolds Number ◽  
Energy Harvesting ◽  
Maximum Amplitude ◽  
Energy Conversion Efficiency ◽  
Circular Cylinders ◽  
Flow Induced Vibration ◽  
Number Range ◽  
Vortex Pattern ◽  
Simulation And Experiment ◽  
Vortex Patterns

The flow-induced vibration (FIV) of multiple cylinders is a common phenomenon in industry and nature. The FIV and energy harvesting of three circular cylinders in tandem are numerically studied by 2D-URANS simulations in Reynolds number range of 30,000 < Re < 105,000. Simulation results match well with experiments in the tested cases. Four branches of FIV are clearly captured in the amplitude and frequency ratio curves of the three cylinders with roughness, including initial branch of vortex-induced vibration (VIV), VIV upper branch, transition from VIV to galloping, and galloping. It is shown that the vortices from downstream cylinder are strongly disrupted and modified by vortices of upstream cylinder. The third cylinder is almost suppressed in VIV initial branch. The 2P vortex pattern is observed for the first cylinder in the VIV upper branch. For Re = 90,000 in the transition regime, the vortex patterns of the first and second cylinders are 2P + 4S and 2P + 2S, respectively. In the galloping branch, the shear layer motion is in synchronization with the motion of the cylinder, and the maximum amplitude of 2.8D is reached by the first cylinder. The total converted power of the three cylinders increases with U*water both in the simulation and experiment. For the three cylinders, the maximum power reaches up to 85.26 W with the increase of Reynolds number. The energy conversion efficiency is stable and higher than 35% in the starting region of VIV upper branch, and the maximum value of 40.41% is obtained when Re = 40,000.

scholarly journals Experimental investigation of flow-induced vibration of a rotating circular cylinder

2017 ◽  
Vol 829 ◽  
pp. 486-511 ◽  
Author(s):  
K. W. L. Wong ◽  
J. Zhao ◽  
D. Lo Jacono ◽  
M. C. Thompson ◽  
J. Sheridan
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Rotation Rate ◽  
Rotating Cylinder ◽  
Flow Induced Vibration ◽  
Amplitude Response ◽  
Number Range ◽  
Rotating Circular Cylinder ◽  
Numerical Predictions

While flow-induced vibration of bluff bodies has been extensively studied over the last half-century, only limited attention has been given to flow-induced vibration of elastically mounted rotating cylinders. Since recent low-Reynolds-number numerical work suggests that rotation can enhance or suppress the natural oscillatory response, the former could find applications in energy harvesting and the latter in vibration control. The present experimental investigation characterises the dynamic response and wake structure of a rotating circular cylinder undergoing vortex-induced vibration at a low mass ratio ($m^{\ast }=5.78$) over the reduced velocity range leading to strong oscillations. The experiments were conducted in a free-surface water channel with the cylinder vertically mounted and attached to a motor that provided constant rotation. Springs and an air-bearing system allow the cylinder to undertake low-damped transverse oscillations. Under cylinder rotation, the normalised frequency response was found to be comparable to that of a freely vibrating non-rotating cylinder. At reduced velocities consistent with the upper branch of a non-rotating transversely oscillating cylinder, the maximum oscillation amplitude increased with non-dimensional rotation rate up to $\unicode[STIX]{x1D6FC}\approx 2$. Beyond this, there was a sharp decrease in amplitude. Notably, this critical value corresponds approximately to the rotation rate at which vortex shedding ceases for a non-oscillating rotating cylinder. Remarkably, at $\unicode[STIX]{x1D6FC}=2$ there was approximately an 80 % increase in the peak amplitude response compared to that of a non-rotating cylinder. The observed amplitude response measured over the Reynolds-number range of ($1100\lesssim Re\lesssim 6300$) is significantly different from numerical predictions and other experimental results recorded at significantly lower Reynolds numbers.

scholarly journals The Effects of Reynolds Number on Energy Harvesting from FIV by a Square Cylinder

2020 ◽  
Vol 38 (5) ◽  
pp. 928-936
Author(s):  
Peng Han ◽  
Guang Pan ◽  
Qiaogao Huang ◽  
Yao SHI
Keyword(s):  
Reynolds Number ◽  
Energy Harvesting ◽  
Energy Conversion ◽  
Reynolds Numbers ◽  
Energy Conversion Efficiency ◽  
Published Data ◽  
Square Cylinder ◽  
A Value ◽  
Vibration Responses ◽  
Intense Vibration

Under the action of incoming flow, the square cylinder can generate more intense vibration responses than the circular cylinder, which is beneficial for energy harvesting. Numerical simulations for FIV of the square-cylinder energy conversion system are carried out. URANS equations are used in conjunction with the shear stress transport k-ω turbulence model to predict the flow, and the equations for vibrations are solved by the Newmark-β algorithm. The present numerical method is validated against the published data with good consistency. The Reduced velocity Ur is varied from 1-20, with corresponding Reynolds numbers of 24 000-160 000. The numerical results indicate that the Reynolds number significantly affects the frequency response, amplitude response, vortex shedding mode, and energy conversion efficiency. The highest efficiency point locates at Re=88 000, with a value of 7.156%. When Re>120 000, the system transits from vortex-induced vibration into galloping, and its vibration responses as well as energy harvesting characteristics change sharply. Fully developed galloping motion occurs when Re>144 000.

Effect of Reynolds Number on Local Scour Around a Monopile in Steady Current

2019 ◽  
Author(s):  
Xiaofan Lou ◽  
Kaibing Zhang ◽  
Zhenhong Chen
Keyword(s):  
Reynolds Number ◽  
Time Scale ◽  
Time History ◽  
Local Scour ◽  
Circular Cylinders ◽  
Scour Depth ◽  
Clear Water ◽  
Number Range ◽  
Steady Current ◽  
Equilibrium Scour Depth

Abstract The effect of Reynolds number (Re) on the local scour around a monopile encountering steady current was investigated experimentally in a water flume. The experiment was performed using circular cylinders with different diameters under two different freestream velocities, covering both clear-water and live-bed scours and a Reynolds number range of approximately 9,000–60,000. The time-series of the scour depth was recorded during the whole scour process and the scour pit was scanned after the scour process reached equilibrium. Results are presented in terms of the equilibrium scour depth, the time-scale of the scour process and the three-dimensional scour profile at different Reynolds numbers. For both clear-water and live-bed scours, the time history of the scour process indicate that the time-scale becomes larger as Re increases. It is also found that the normalized equilibrium scour depth, as well as the normalized scour radius, decrease with the increasing Re. An empirical equation of the equilibrium scour depth is derived as a function of Reynolds number based on the experimental results so as to better account for Re effect in the scour design.

The effects of surface roughness on the flow past circular cylinders at high Reynolds numbers

1982 ◽  
Vol 123 ◽  
pp. 363-378 ◽  
Author(s):  
Y. Nakamura ◽  
Y. Tomonari
Keyword(s):  
Reynolds Number ◽  
Circular Cylinder ◽  
High Reynolds Number ◽  
Circular Cylinders ◽  
Similarity Parameter ◽  
Number Range ◽  
Pressure Distributions ◽  
Mean Pressure ◽  
Supercritical Range ◽  
High Reynolds

Measurements of’ the mean-pressure distribution and the Strouhal number on a smooth circular cylinder, circular cylinders with distributed roughness, and circular cylinders with narrow roughness strips were made over a Reynolds-number range 4.0 × l04 to 1.7 × l06 in a uniform flow. A successful high-Reynolds-number (trans- critical) simulation for a smooth circular cylinder is obtained using a smooth circular cylinder with roughness strips. High-Reynolds-number simulation can only be obtained by roughness strips and not by distributed roughness. A similarity parameter correlating the pressure distributions on circular cylinders with distributed roughness in the supercritical range is presented. The same parameter can also be applicable to the drag coefficients of spheres with distributed roughness.

Vortex Excited Oscillations of Yawed Circular Cylinders

1977 ◽  
Vol 99 (3) ◽  
pp. 495-501 ◽  
Author(s):  
R. King
Keyword(s):  
Reynolds Number ◽  
Theoretical Work ◽  
Circular Cylinders ◽  
Stability Criteria ◽  
Local Flow ◽  
Braced Frame ◽  
Flowing Fluid ◽  
Number Range ◽  
Drag Forces ◽  
The Stability

Yawed cylinders are cylinders inclined forward or backwards in the plane of the flowing fluid. They are used in many practical situations such as braced frame members and raked marine piles. This paper describes an examination of three aspects of the yawed cylinder-fluid interactions over a range of yaw angles ±45° from the vertical for the Reynolds number range 2,000 < Re < 20,000. viz. 1. Establishment of the stability criteria of vortex-excited oscillations. 2. Measurement of ‘steady’ drag forces and equivalent drag coefficients. 3. Visualization of the local flow over stationary and oscillating cylinder. After a brief review of previous experimental and theoretical work, the results of the three items listed above are presented and discussed. Vortex-excited oscillations were recorded in the in-line and crossflow directions throughout the range of yaw angles and the results of items 2, 3 were used to justify the forms of the stability criteria proposed for these oscillations.

A note on vortex streets behind circular cylinders at low Reynolds numbers

1971 ◽  
Vol 45 (1) ◽  
pp. 203-208 ◽  
Author(s):  
D. J. Tritton
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Circular Cylinders ◽  
Number Range ◽  
Low Reynolds Numbers ◽  
Current State ◽  
Reynolds Number Range ◽  
Vortex Streets ◽  
Low Reynolds

A discussion is given of the current state of knowledge of vortex streets behind circular cylinders in the Reynolds number range 50 to 160. This was prompted by Gaster's (1969) report that he could not find the transition at a Reynolds number of about 90 observed by Tritton (1959) and Berger (1964a). A further brief experiment confirming the existence of the transition is described Reasons for rejecting Gaster's interpretation are advanced. Possible (mutually alternative) explanations of the discrepant observations are suggested.

Global frequency selection in the observed time-mean wakes of circular cylinders

2008 ◽  
Vol 601 ◽  
pp. 425-441 ◽  
Author(s):  
MOSES KHOR ◽  
JOHN SHERIDAN ◽  
MARK C. THOMPSON ◽  
KERRY HOURIGAN
Keyword(s):  
Reynolds Number ◽  
Three Dimensional ◽  
Reynolds Numbers ◽  
Linear Instability ◽  
Circular Cylinders ◽  
Near Wake ◽  
Mean Velocity ◽  
Number Range ◽  
Wake Instability ◽  
Karman Vortex

Observations have been made of the time-mean velocity profile at midspan in the near-wake of circular cylinders at moderate Reynolds numbers between 600 and 4600, well beyond the Reynolds number of approximately 200 at which the wake becomes three-dimensional. The measured profiles are found to be represented quite accurately by a family of function profiles with known linear instability characteristics. The complex instability frequency is then determined as a function of wake position, using the function profiles. In general, the near wake undergoes a transition from convective to absolute instability; the distance downstream to the point of transition is found to increase over the Reynolds number range investigated. The emergence of a significant region of convective instability is consistent with the known appearance of Bloor–Gerrard vortices. The selected frequency of the wake instability is determined by the saddle-point criterion; the Strouhal numbers for Bénard–von Kármán vortex shedding are found to compare well with the values in the literature.

Vortex-Induced Vibrations and Wake Structures of Isolated Plain and Straked Cylinders Mounted on a 2DOF Elastic Base

2010 ◽  
Author(s):  
Ivan Korkischko ◽  
Cesar M. Freire ◽  
Julio R. Meneghini ◽  
Ricardo Franciss
Keyword(s):  
Reynolds Number ◽  
Degrees Of Freedom ◽  
Particle Image ◽  
Maximum Amplitude ◽  
Elastic Base ◽  
Digital Particle Image Velocimetry ◽  
Circular Cylinders ◽  
Amplitude Response ◽  
Vortex Induced Vibrations ◽  
Image Velocimetry

This paper presents experimental results concerning the response of plain and straked circular cylinders. The isolated cylinders are mounted in a two degrees of freedom elastic base. Two straked cylinders are tested and they have the same pitch p = 10d and two different heights h = 0.1d and h = 0.2d. The longitudinal and transverse amplitude responses and wake structures of plain and helically straked cylinders are compared. The wake visualization uses the stereoscopic digital particle image velocimetry (SDPIV) technique. Comparing to the plain cylinder response, the p = 10d and h = 0.1d strakes moderately reduce the maximum amplitude response, while the p = 10d and h = 0.2d strakes suppress the vortex-induced vibrations. The strake effectiveness is directly related to the strake height. The Reynolds number varies from 1000 up to 7500 in the experiments.

Flow induced vibration of two rigidly connected circular cylinders in different arrangements at a low Reynolds number

2020 ◽  
Vol 217 ◽  
pp. 107741
Author(s):  
Yun Gao ◽  
Bin Yang ◽  
Hongjun Zhu ◽  
Geng Peng ◽  
Zhuangzhuang Zhang ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Circular Cylinders ◽  
Flow Induced Vibration ◽  
Low Reynolds
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