Journal articles: 'Wake Induced Vibration (WIV)'

1

ASSI, G. R. S., P. W. BEARMAN, and J. R. MENEGHINI. "On the wake-induced vibration of tandem circular cylinders: the vortex interaction excitation mechanism." Journal of Fluid Mechanics 661 (August 16, 2010): 365–401. http://dx.doi.org/10.1017/s0022112010003095.

Full text

Abstract:

The mechanism of wake-induced vibrations (WIV) of a pair of cylinders in a tandem arrangement is investigated by experiments. A typical WIV response is characterized by a build-up of amplitude persisting to high reduced velocities; this is different from a typical vortex-induced vibration (VIV) response, which occurs in a limited resonance range. We suggest that WIV of the downstream cylinder is excited by the unsteady vortex–structure interactions between the body and the upstream wake. Coherent vortices interfering with the downstream cylinder induce fluctuations in the fluid force that are not synchronized with the motion. A favourable phase lag between the displacement and the fluid force guarantees that a positive energy transfer from the flow to the structure sustains the oscillations. If the unsteady vortices are removed from the wake of the upstream body then WIV will not be excited. An experiment performed in a steady shear flow turned out to be central to the understanding of the origin of the fluid forces acting on the downstream cylinder.

APA, Harvard, Vancouver, ISO, and other styles

2

Zhang, Min, and Junlei Wang. "Experimental Study on Piezoelectric Energy Harvesting from Vortex-Induced Vibrations and Wake-Induced Vibrations." Journal of Sensors 2016 (2016): 1–7. http://dx.doi.org/10.1155/2016/2673292.

Full text

Abstract:

A rigid circular cylinder with two piezoelectric beams attached on has been tested through vortex-induced vibrations (VIV) and wake-induced vibrations (WIV) by installing a big cylinder fixed upstream, in order to study the influence of the different flow-induced vibrations (FIV) types. The VIV test shows that the output voltage increases with the increases of load resistance; an optimal load resistance exists for the maximum output power. The WIV test shows that the vibration of the small cylinder is controlled by the vortex frequency of the large one. There is an optimal gap of the cylinders that can obtain the maximum output voltage and power. For a same energy harvesting device, WIV has higher power generation capacity; then the piezoelectric output characteristics can be effectively improved.

APA, Harvard, Vancouver, ISO, and other styles

3

Assi, G. R. S., P. W. Bearman, B. S. Carmo, J. R. Meneghini, S. J. Sherwin, and R. H. J. Willden. "The role of wake stiffness on the wake-induced vibration of the downstream cylinder of a tandem pair." Journal of Fluid Mechanics 718 (February 8, 2013): 210–45. http://dx.doi.org/10.1017/jfm.2012.606.

Full text

Abstract:

AbstractWhen a pair of tandem cylinders is immersed in a flow the downstream cylinder can be excited into wake-induced vibrations (WIV) due to the interaction with vortices coming from the upstream cylinder. Assi, Bearman & Meneghini (J. Fluid Mech., vol. 661, 2010, pp. 365–401) concluded that the WIV excitation mechanism has its origin in the unsteady vortex–structure interaction encountered by the cylinder as it oscillates across the wake. In the present paper we investigate how the cylinder responds to that excitation, characterising the amplitude and frequency of response and its dependency on other parameters of the system. We introduce the concept of wake stiffness, a fluid dynamic effect that can be associated, to a first approximation, with a linear spring with stiffness proportional to $\mathit{Re}$ and to the steady lift force occurring for staggered cylinders. By a series of experiments with a cylinder mounted on a base without springs we verify that such wake stiffness is not only strong enough to sustain oscillatory motion, but can also dominate over the structural stiffness of the system. We conclude that while unsteady vortex–structure interactions provide the energy input to sustain the vibrations, it is the wake stiffness phenomenon that defines the character of the WIV response.

APA, Harvard, Vancouver, ISO, and other styles

4

Zhao, Enjin, Xiaoyu Xia, Fengyuan Jiang, Haiwen Tu, and Lin Mu. "Effect of porous media on wake-induced vibration (WIV) in tandem circular cylinder." Ocean Engineering 249 (April 2022): 110900. http://dx.doi.org/10.1016/j.oceaneng.2022.110900.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Cao, Dongxing, Junru Wang, Xiangying Guo, S. K. Lai, and Yongjun Shen. "Recent advancement of flow-induced piezoelectric vibration energy harvesting techniques: principles, structures, and nonlinear designs." Applied Mathematics and Mechanics 43, no. 7 (July 2022): 959–78. http://dx.doi.org/10.1007/s10483-022-2867-7.

Full text

Abstract:

AbstractEnergy harvesting induced from flowing fluids (e.g., air and water flows) is a well-known process, which can be regarded as a sustainable and renewable energy source. In addition to traditional high-efficiency devices (e.g., turbines and watermills), the micro-power extracting technologies based on the flow-induced vibration (FIV) effect have sparked great concerns by virtue of their prospective applications as a self-power source for the microelectronic devices in recent years. This article aims to conduct a comprehensive review for the FIV working principle and their potential applications for energy harvesting. First, various classifications of the FIV effect for energy harvesting are briefly introduced, such as vortex-induced vibration (VIV), galloping, flutter, and wake-induced vibration (WIV). Next, the development of FIV energy harvesting techniques is reviewed to discuss the research works in the past three years. The application of hybrid FIV energy harvesting techniques that can enhance the harvesting performance is also presented. Furthermore, the nonlinear designs of FIV-based energy harvesters are reported in this study, e.g., multi-stability and limit-cycle oscillation (LCO) phenomena. Moreover, advanced FIV-based energy harvesting studies for fluid engineering applications are briefly mentioned. Finally, conclusions and future outlook are summarized.

APA, Harvard, Vancouver, ISO, and other styles

6

Garg, Hemanshul, Atul Kumar Soti, and Rajneesh Bhardwaj. "Thermal buoyancy induced suppression of wake-induced vibration." International Communications in Heat and Mass Transfer 118 (November 2020): 104790. http://dx.doi.org/10.1016/j.icheatmasstransfer.2020.104790.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Zhao, Daoli, Jie Zhou, Ting Tan, Zhimiao Yan, Weipeng Sun, Junlian Yin, and Wenming Zhang. "Hydrokinetic piezoelectric energy harvesting by wake induced vibration." Energy 220 (April 2021): 119722. http://dx.doi.org/10.1016/j.energy.2020.119722.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Lee, H., K. Hourigan, and M. C. Thompson. "Vortex-induced vibration of a neutrally buoyant tethered sphere." Journal of Fluid Mechanics 719 (February 19, 2013): 97–128. http://dx.doi.org/10.1017/jfm.2012.634.

Full text

Abstract:

AbstractA combined numerical and experimental study examining vortex-induced vibration (VIV) of a neutrally buoyant tethered sphere has been undertaken. The study covered the Reynolds-number range $50\leq \mathit{Re}\lesssim 12\hspace{0.167em} 000$, with the numerical ($50\leq \mathit{Re}\leq 800$) and experimental ($370\leqslant \mathit{Re}\lesssim 12\hspace{0.167em} 000$) ranges overlapping. Neutral buoyancy was chosen to eliminate one parameter, i.e. the influence of gravity, on the VIV behaviour, although, of course, the effect of added mass remains. The tether length was also chosen to be sufficiently long so that, to a good approximation, the sphere was constrained to move within a plane. Seven broad but relatively distinct sphere oscillation and wake states could be distinguished. For regime I, the wake is steady and axisymmetric, and it undergoes transition to a steady two-tailed wake in regime II at $\mathit{Re}= 210$. Those regimes are directly analogous to those of a fixed sphere. Once the sphere begins to vibrate at $\mathit{Re}\simeq 270$ in regime III, the wake behaviour is distinct from the fixed-sphere wake. Initially the vibration frequency of the sphere is half the shedding frequency in the wake, with the latter consistent with the fixed-sphere wake frequency. The sphere vibration is not purely periodic but modulated over several base periods. However, at slightly higher Reynolds numbers ($\mathit{Re}\simeq 280$), planar symmetry is broken, and the vibration shifts to the planar normal (or azimuthal) direction, and becomes completely azimuthal at the start of regime IV at $\mathit{Re}= 300$. In comparison, for a fixed sphere, planar symmetry is broken at a much higher Reynolds number of $\mathit{Re}\simeq 375$. Interestingly, planar symmetry returns to the wake for $\mathit{Re}\gt 330$, in regime V, for which the oscillations are again radial, and is maintained until $\mathit{Re}= 450$ or higher. At the same time, the characteristic vortex loops in the wake become symmetrical, i.e. two-sided. For $\mathit{Re}\gt 500$, in regime VI, the trajectory of the sphere becomes irregular, possibly chaotic. That state is maintained over the remaining Reynolds-number range simulated numerically ($\mathit{Re}\leq 800$). Experiments overlapping this Reynolds-number range confirm the amplitude radial oscillations in regime V and the chaotic wandering for regime VI. At still higher Reynolds numbers of $\mathit{Re}\gt 3000$, in regime VII, the trajectories evolve to quasi-circular orbits about the neutral point, with the orbital radius increasing as the Reynolds number is increased. At $\mathit{Re}= 12\hspace{0.167em} 000$, the orbital diameter reaches approximately one sphere diameter. Of interest, this transition sequence is distinct from that for a vertically tethered heavy sphere, which undergoes transition to quasi-circular orbits beyond $\mathit{Re}= 500$.

APA, Harvard, Vancouver, ISO, and other styles

9

Zhu, S., Y. Cai, and S. S. Chen. "Experimental Fluid-Force Coefficients for Wake-Induced Cylinder Vibration." Journal of Engineering Mechanics 121, no. 9 (September 1995): 1003–15. http://dx.doi.org/10.1061/(asce)0733-9399(1995)121:9(1003).

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Assi, Gustavo R. S. "Wake-induced vibration of tandem cylinders of different diameters." Journal of Fluids and Structures 50 (October 2014): 329–39. http://dx.doi.org/10.1016/j.jfluidstructs.2014.07.001.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Zhao, Ming, Zhendong Cui, Kenny Kwok, and Yu Zhang. "Wake-induced vibration of a small cylinder in the wake of a large cylinder." Ocean Engineering 113 (February 2016): 75–89. http://dx.doi.org/10.1016/j.oceaneng.2015.12.032.

Full text

APA, Harvard, Vancouver, ISO, and other styles

12

Meng, Jinpeng, Xingwen Fu, Chongqiu Yang, Leian Zhang, Xianhai Yang, and Rujun Song. "Design and simulation investigation of piezoelectric energy harvester under wake-induced vibration coupling vortex-induced vibration." Ferroelectrics 585, no. 1 (December 10, 2021): 128–38. http://dx.doi.org/10.1080/00150193.2021.1991221.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Hossein Rabiee, Amir, Farzad Rafieian, and Amir Mosavi. "Active vibration control of tandem square cylinders for three different phenomena: Vortex-induced vibration, galloping, and wake-induced vibration." Alexandria Engineering Journal 61, no. 12 (December 2022): 12019–37. http://dx.doi.org/10.1016/j.aej.2022.05.048.

Full text

APA, Harvard, Vancouver, ISO, and other styles

14

Zhou, Chao, and Yibing Liu. "Modeling and Mechanism of Rain-Wind Induced Vibration of Bundled Conductors." Shock and Vibration 2016 (2016): 1–7. http://dx.doi.org/10.1155/2016/1038150.

Full text

Abstract:

Under the certain rain-wind conditions, bundled conductors exhibit a rain-wind induced large-amplitude vibration. This type of vibration can cause the fatigue fractures of conductors and fatigue failures of spacers, which threaten the safety operation and serviceability of high-voltage transmission line. To reveal the mechanism of rain-wind induced vibration of bundled conductors, a series of 2-dimensional CFD models about the twin bundled conductors with rivulets are developed to obtain the curves of aerodynamic coefficients with the upper rivulet angle. The influences of the forward conductor’s aerodynamic shielding and the upper rivulet’s aerodynamic characteristics on the leeward conductor are discussed. Furthermore, a 2-dimensional 3DOF model for the rain-wind induced vibration of the leeward conductor is established. The model is solved by finite element method and Newmark method, and the effects of the wind velocity and the upper rivulet’s motion on vibration amplitude of the leeward conductor are analyzed. By contrast with the wake-induced vibration, it can easily find that the characteristics of rain-wind vibration are obviously different from those of the wake-induced vibration, and the main reason of the rain-induced vibration may be due to the upper rivulet’s motion.

APA, Harvard, Vancouver, ISO, and other styles

15

Muhammad Ridhwaan Hassim, Mohd Azan Mohammed Sapardi, Nur Marissa Kamarul Baharin, Syed Noh Syed Abu Bakar, Muhammad Abdullah, and Khairul Affendy Mohd Nor. "CFD Modelling of Wake-Induced Vibration At Low Reynolds Number." CFD Letters 13, no. 11 (November 11, 2021): 53–64. http://dx.doi.org/10.37934/cfdl.13.11.5364.

Full text

Abstract:

Flow-induced vibration is an enthralling phenomenon in the field of engineering. Numerous studies have been conducted on converting flow kinetic energy to electrical energy using the fundamental. Wake-induced vibration is one of the configurations used to optimise the generation of electricity. The results of the study on the effect of the gap between the multiple bluff bodies will provide insight into optimising the energy harvesting process. This study focuses on fluid behaviour and response behind two circular cylinders arranged in tandem when interacting with a fluid flow at low Reynolds numbers ranging from 200 to 1000. The study has been done on several gap lengths between the two cylinders, between 2D and 5D. The study was carried out numerically by using OpenFOAM. At Re = 1000, it is found that the gap length of 2.5D is optimal in terms of producing the highest lift force coefficient on the downstream circular cylinder.

APA, Harvard, Vancouver, ISO, and other styles

16

Shavnya, R. A., and A. N. Danilin. "Wake-induced vibration of two-phase conductors connected by spacers." IOP Conference Series: Materials Science and Engineering 1129, no. 1 (April 1, 2021): 012040. http://dx.doi.org/10.1088/1757-899x/1129/1/012040.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

Pettigrew, M. J., and C. E. Taylor. "Two-Phase Flow-Induced Vibration: An Overview (Survey Paper)." Journal of Pressure Vessel Technology 116, no. 3 (August 1, 1994): 233–53. http://dx.doi.org/10.1115/1.2929583.

Full text

Abstract:

Two-phase flow exists in many industrial components. To avoid costly vibration problems, sound technology in the area of two-phase flow-induced vibration is required. This paper is an overview of the principal mechanisms governing vibration in two-phase flow. Dynamic parameters such as hydrodynamic mass and damping are discussed. Vibration excitation mechanisms in axial flow are outlined. These include fluidelastic instability, phase-change noise, and random excitation. Vibration excitation mechanisms in cross-flow, such as fluidelastic instability, periodic wake shedding, and random excitation, are reviewed.

APA, Harvard, Vancouver, ISO, and other styles

18

Maruai, Nurshafinaz Mohd, Mohamed Sukri Mat Ali, Mohamad Hafiz Ismail, and Sheikh Ahmad Zaki Shaikh Salim. "Downstream flat plate as the flow-induced vibration enhancer for energy harvesting." Journal of Vibration and Control 24, no. 16 (May 22, 2017): 3555–68. http://dx.doi.org/10.1177/1077546317707877.

Full text

Abstract:

The prospect of harvesting energy from flow-induced vibration using an elastic square cylinder with a detached flat plate is experimentally investigated. The feasibility of flow-induced vibration to supply an adequate base excitation for micro-scale electrical power generation is assessed through a series of wind tunnel tests. The current test model of a single square cylinder is verified through a comparable pattern of vibration amplitude response with previous experimental study and two-dimensional numerical simulations based on the unsteady Reynolds averaged Navier–Stokes (URANS). In addition, a downstream flat plate is included in the wake of the square cylinder to study the effects of wake interference upon flow-induced vibration. A downstream flat plate is introduced as the passive vibration control to enhance the magnitude of flow-induced vibration and simultaneously increases the prospect of harvesting energy from the airflow. The study is conducted by varying the gap separation between the square cylinder and flat plate for 0.1≤ G/ D ≤3. The highest peak amplitude is observed for the gap G/ D = 1.2 with yrms/ D = 0.46 at UR = 17, which is expected to harvest ten times more energy than the single square cylinder. The high amplitude vibration response is sustained within a relatively broader range of lock-in synchronization. Meanwhile, for G/ D = 2 the vibration is suppressed, which leads to a lower magnitude of harvested energy. Contrarily, the amplitude response pattern for G/ D = 3 is in agreement with the single square cylinder. Hence, the flat plate has no significance to the wake interference of the square cylinder when the gap separation is beyond 3 D.

APA, Harvard, Vancouver, ISO, and other styles

19

Peltzer, R. D., and D. M. Rooney. "Near Wake Properties of a Strumming Marine Cable: An Experimental Study." Journal of Fluids Engineering 107, no. 1 (March 1, 1985): 86–91. http://dx.doi.org/10.1115/1.3242446.

Full text

Abstract:

Resonant flow-induced oscillations of a flexible cable can occur when the damping of the cable system is sufficiently small. The changes in the flow field that occur in the near wake of the cable during these resonant oscillations are closely related to the changes in the fluid forces that accompany these oscillations. The present wind tunnel experiments were undertaken to examine the effects that forced synchronized vibration and the helically-wound cross section of the cable have on near wake vortex shedding-related parameters; specifically the shedding frequency, vortex formation length Lf, reduced velocity Ur, vortex strength and the wake width Lw. The range of flow speeds over which the vortex shedding was locked on to the vibration frequency varied directly with the vibration amplitude. The helical cross section and the synchronized vibration caused significant changes in the near wake development that could be directly related to the increase in hydrodynamic forces associated with unforced synchronized vibration.

APA, Harvard, Vancouver, ISO, and other styles

20

Janocha, Marek Jan, Muk Chen Ong, and Guang Yin. "Large eddy simulations and modal decomposition analysis of flow past a cylinder subject to flow-induced vibration." Physics of Fluids 34, no. 4 (April 2022): 045119. http://dx.doi.org/10.1063/5.0084966.

Full text

Abstract:

Large eddy simulations (LES) are carried out to investigate the flow around a vibrating cylinder in the subcritical Reynolds number regime at Re = 3900. Three reduced velocities, Ur = 3, 5, and 7, are chosen to investigate the wake structures in different branches of a vortex-induced vibration (VIV) lock-in. The instantaneous vortical structures are identified to show different coherent flow structures in the wake behind the vibrating cylinder for various branches of VIV lock-in. The combined effects of the frequency and amplitude of the oscillation on the flow pattern in the wake region, the hydrodynamic quantities of the cylinder, and the spanwise length scale of the energetic wake flow structures are discussed in detail. It is found that the typical spanwise lengths of the flow structures are [Formula: see text] at Ur = 5 and [Formula: see text] at [Formula: see text] in the near-wake region and level out at [Formula: see text] further downstream. Furthermore, multiscale proper orthogonal decomposition (mPOD) is used to analyze the dominant flow features in the wake region. With the increasing Ur, the total kinetic energy contribution of superharmonic modes increases and the contribution of subharmonic modes decreases. The dominant flow characteristics associated with the vortex shedding and their super harmonics, and the low-frequency modulation of the wake flow can be captured by the mPOD modes.

APA, Harvard, Vancouver, ISO, and other styles

21

Yan, Zhimiao, Guangwei Shi, Jie Zhou, Lingzhi Wang, Lei Zuo, and Ting Tan. "Wind piezoelectric energy harvesting enhanced by elastic-interfered wake-induced vibration." Energy Conversion and Management 249 (December 2021): 114820. http://dx.doi.org/10.1016/j.enconman.2021.114820.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

KAWABATA, Yusuke, Naoto KATO, Mizuyasu KOIDE, Tsutomu TAKAHASHI, and Masataka SHIRAKASHI. "113 Influence of a wake body on Karman vortex induced vibration." Proceedings of Conference of Hokuriku-Shinetsu Branch 2010.47 (2010): 25–26. http://dx.doi.org/10.1299/jsmehs.2010.47.25.

Full text

APA, Harvard, Vancouver, ISO, and other styles

23

Kim, Sangil, Md Mahbub Alam, and Dilip Kumar Maiti. "Wake and suppression of flow-induced vibration of a circular cylinder." Ocean Engineering 151 (March 2018): 298–307. http://dx.doi.org/10.1016/j.oceaneng.2018.01.043.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Lau, Y. L., R. M. C. So, and R. C. K. Leung. "Flow-induced vibration of elastic slender structures in a cylinder wake." Journal of Fluids and Structures 19, no. 8 (November 2004): 1061–83. http://dx.doi.org/10.1016/j.jfluidstructs.2004.06.007.

Full text

APA, Harvard, Vancouver, ISO, and other styles

25

Alam, Md Mahbub. "Effects of Mass and Damping on Flow-Induced Vibration of a Cylinder Interacting with the Wake of Another Cylinder at High Reduced Velocities." Energies 14, no. 16 (August 20, 2021): 5148. http://dx.doi.org/10.3390/en14165148.

Full text

Abstract:

Flow-induced vibration is a canonical issue in various engineering fields, leading to fatigue or immediate damage to structures. This paper numerically investigates flow-induced vibrations of a cylinder interacting with the wake of another cylinder at a Reynolds number Re = 150. It sheds light on the effects of mass ratio m*, damping ratio, and mass-damping ratio m*ζ on vibration amplitude ratio A/D at different reduced velocities Ur and cylinder spacing ratios L/D = 1.5 and 3.0. A couple of interesting observations are made. The m* has a greater influence on A/D than ζ although both m* and ζ cause reductions in A/D. The m* effect on A/D is strong for m* = 2–16 but weak for m* > 16. As opposed to a single isolated cylinder case, the mass-damping m*ζ is not found to be a unique parameter for a cylinder oscillating in a wake. The vortices in the wake decay rapidly at small ζ. Alternate reattachment of the gap shear layers on the wake cylinder fuels the vibration of the wake cylinder for L/D = 1.5 while the impingement and switch of the gap vortices do the same for L/D = 3.0.

APA, Harvard, Vancouver, ISO, and other styles

26

Tian, Jin, Paul Croaker, Jiasheng Li, and Hongxing Hua. "Experimental and numerical studies on the flow-induced vibration of propeller blades under nonuniform inflow." Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 231, no. 2 (June 17, 2016): 481–95. http://dx.doi.org/10.1177/1475090216654306.

Full text

Abstract:

This article presents the experimental and numerical studies on the flow-induced vibration of propeller blades under periodic inflows. A total of two 7-bladed highly skewed model propellers of identical geometries but different elastic characteristics were operated in four-cycle and six-cycle inflows to study the blade vibratory strain response. A total of two kinds of wire mesh wake screens located 400 mm upstream of the propeller plane were used to generate four-cycle and six-cycle inflows. A laser Doppler velocimetry system located 100 mm downstream of the wake screen plane was used to measure the axial velocity distributions produced by the wake screens. Strain gauges were bonded onto the propeller blades in different positions. Data from strain gauges quantified vibratory strain amplitudes and excitation frequencies induced by the wake screens. The propellers were accelerated through the flexible propeller’s fundamental frequency to investigate the effect of resonance on vibratory strain response. The numerical work was conducted using large eddy simulation and moving mesh technique to predict the unsteady forces acting on the propeller blade when operating in a nonuniform inflow.

APA, Harvard, Vancouver, ISO, and other styles

27

Su, Zhi Bin, and Sheng Nan Sun. "Vortex-Induced Dynamic Response of Submerged Floating Tunnel Tether Based on Wake Oscillator Model." Advanced Materials Research 919-921 (April 2014): 1262–65. http://dx.doi.org/10.4028/www.scientific.net/amr.919-921.1262.

Full text

Abstract:

To study the vibration response of submerged floating tunnel tether under the combined action of vortex-induced vibration and parametric vibration, a non-linear vibration equation based on wake oscillator model is set up taking the geometric nonlinearity of tether into account, in which effect of tube on tether is simplified as axial excitation. An approximate numerical solution of planning submerged floating tunnel tether is obtained by applying Galerkin method and Runge-kutta method. The variation degree of mid-span displacement response and axial force of tether is analyzed when the vortex-induced resonance and parametric resonance occur. The results show that, when vortex-induced resonance and parametric resonance occur simultaneously, the mid-span displacement and axial force of tether increase dramatically; the tether sag effect results in the asymmetry of tether mid-span vibration amplitude.

APA, Harvard, Vancouver, ISO, and other styles

28

Zhao, J., K. Hourigan, and M. C. Thompson. "Flow-induced vibration of D-section cylinders: an afterbody is not essential for vortex-induced vibration." Journal of Fluid Mechanics 851 (July 20, 2018): 317–43. http://dx.doi.org/10.1017/jfm.2018.501.

Full text

Abstract:

While it has been known that an afterbody (i.e. the structural part of a bluff body downstream of the flow separation points) plays an important role affecting the wake characteristics and even may change the nature of the flow-induced vibration (FIV) of a structure, the question of whether an afterbody is essential for the occurrence of one particular common form of FIV, namely vortex-induced vibration (VIV), still remains. This has motivated the present study to experimentally investigate the FIV of an elastically mounted forward- or backward-facing D-section (closed semicircular) cylinder over the reduced velocity range $2.3\leqslant U^{\ast }\leqslant 20$, where $U^{\ast }=U/(f_{nw}D)$. Here, $U$ is the free-stream velocity, $D$ the cylinder diameter and $f_{nw}$ the natural frequency of the system in quiescent fluid (water). The normal orientation with the body’s flat surface facing upstream is known to be subject to another common form of FIV, galloping, while the reverse D-section with the body’s curved surface facing upstream, due to the lack of an afterbody, has previously been reported to be immune to VIV. The fluid–structure system was modelled on a low-friction air-bearing system in conjunction with a recirculating water channel facility to achieve a low mass ratio (defined as the ratio of the total oscillating mass to that of the displaced fluid mass). Interestingly, through a careful overall examination of the dynamic responses, including the vibration amplitude and frequency, fluid forces and phases, our new findings showed that the D-section exhibits a VIV-dominated response for $U^{\ast }<10$, galloping-dominated response for $U^{\ast }>12.5$, and a transition regime with a VIV–galloping interaction in between. Also observed for the first time were interesting wake modes associated with these response regimes. However, in contrast to previous studies at high Reynolds number (defined by $Re=UD/\unicode[STIX]{x1D708}$, with $\unicode[STIX]{x1D708}$ the kinematic viscosity), which have showed that the D-section was subject to ‘hard’ galloping that required a substantial initial amplitude to trigger, it was observed in the present study that the D-section can gallop softly from rest. Surprisingly, on the other hand, it was found that the reverse D-section exhibits pure VIV features. Remarkable similarities were observed in a direct comparison with a circular cylinder of the same mass ratio, in terms of the onset $U^{\ast }$ of significant vibration, the peak amplitude (only approximately 6 % less than that of the circular cylinder), and also the fluid forces and phases. Of most significance, this study shows that an afterbody is not essential for VIV at low mass and damping ratios.

APA, Harvard, Vancouver, ISO, and other styles

29

McCluskey, Connor J., Manton J. Guers, and Stephen C. Conlon. "Extreme value statistics of flow-induced hydrofoil vibration and resonance." Noise Control Engineering Journal 69, no. 1 (January 1, 2021): 18–29. http://dx.doi.org/10.3397/1/37692.

Full text

Abstract:

Flow-induced noise and vibration produce cyclic loading on structures such as wind turbines, propellers, and vehicle control surfaces. This cyclic loading can produce fatigue damage in these structures. Additionally, large outlier loads can potentially exceed maximum design levels. Most other works have focused on the extreme value statistics of random loads, and there is limited work which considers the influence of structural resonances. The goal of this work was to study the influence of low order mode responses on extreme response statistics. To accomplish this, the flow-induced vibration response of cantilever fins forced by the wake of an upstream flow obstruction was measured in a closed-circuit water tunnel. The tunnel flow speed was increased, so the wake would excite the first bending mode. A maxima data set was determined from the measured response using the block maxima method, and the generalized extreme value (GEV) distribution was applied to each flow speed. Data were then filtered into stiffness-controlled and damping-controlled responses, and the extreme value analysis was repeated. Results indicated that the extreme response was influenced more by the damping-controlled response than the stiffness-controlled response. When excited, extreme responses from structural resonances must be considered in maximum load design.

APA, Harvard, Vancouver, ISO, and other styles

30

Mureithi, Njuki W. "Karman Wake Dynamics and Vortex Induced Vibration Control : A Nonlinear Dynamics Perspective." Proceedings of the Dynamics & Design Conference 2008 (2008): _B1–1_—_B1–6_. http://dx.doi.org/10.1299/jsmedmc.2008._b1-1_.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Deng, Yangchen, Shouying Li, and Zhengqing Chen. "Unsteady Theoretical Analysis on the Wake-Induced Vibration of Suspension Bridge Hangers." Journal of Bridge Engineering 24, no. 2 (February 2019): 04018113. http://dx.doi.org/10.1061/(asce)be.1943-5592.0001339.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Law, Yun Zhi, and Rajeev Kumar Jaiman. "Wake stabilization mechanism of low-drag suppression devices for vortex-induced vibration." Journal of Fluids and Structures 70 (April 2017): 428–49. http://dx.doi.org/10.1016/j.jfluidstructs.2017.02.005.

Full text

APA, Harvard, Vancouver, ISO, and other styles

33

Bourguet, Rémi, and David Lo Jacono. "Flow-induced vibrations of a rotating cylinder." Journal of Fluid Mechanics 740 (February 6, 2014): 342–80. http://dx.doi.org/10.1017/jfm.2013.665.

Full text

Abstract:

AbstractThe flow-induced vibrations of a circular cylinder, free to oscillate in the cross-flow direction and subjected to a forced rotation about its axis, are analysed by means of two- and three-dimensional numerical simulations. The impact of the symmetry breaking caused by the forced rotation on the vortex-induced vibration (VIV) mechanisms is investigated for a Reynolds number equal to $100$, based on the cylinder diameter and inflow velocity. The cylinder is found to oscillate freely up to a rotation rate (ratio between the cylinder surface and inflow velocities) close to $4$. Under forced rotation, the vibration amplitude exhibits a bell-shaped evolution as a function of the reduced velocity (inverse of the oscillator natural frequency) and reaches $1.9$ diameters, i.e. three times the maximum amplitude in the non-rotating case. The free vibrations of the rotating cylinder occur under a condition of wake–body synchronization similar to the lock-in condition driving non-rotating cylinder VIV. The largest vibration amplitudes are associated with a novel asymmetric wake pattern composed of a triplet of vortices and a single vortex shed per cycle, the ${\rm T} + {\rm S}$ pattern. In the low-frequency vibration regime, the flow exhibits another new topology, the U pattern, characterized by a transverse undulation of the spanwise vorticity layers without vortex detachment; consequently, free oscillations of the rotating cylinder may also develop in the absence of vortex shedding. The symmetry breaking due to the rotation is shown to directly impact the selection of the higher harmonics appearing in the fluid force spectra. The rotation also influences the mechanism of phasing between the force and the structural response.

APA, Harvard, Vancouver, ISO, and other styles

34

HOVER, F. S., H. TVEDT, and M. S. TRIANTAFYLLOU. "Vortex-induced vibrations of a cylinder with tripping wires." Journal of Fluid Mechanics 448 (November 26, 2001): 175–95. http://dx.doi.org/10.1017/s0022112001005985.

Full text

Abstract:

Thin wires are attached on the outer surface and parallel to the axis of a smooth circular cylinder in a steady cross-stream, modelling the effect of protrusions and attachments. The impact of the wires on wake properties, and vortex-induced loads and vibration are studied at Reynolds numbers up to 4.6 × 104, with 3.0 × 104 as a focus point. For a stationary cylinder, wires cause significant reductions in drag and lift coefficients, as well as an increase in the Strouhal number to a value around 0.25–0.27. For a cylinder forced to oscillate harmonically, the main observed wire effects are: (a) an earlier onset of frequency lock-in, when compared with the smooth cylinder case; (b) at moderate amplitude/cylinder diameter (A/D) ratios (0.2 and 0.5), changes in the phase of wake velocity and of lift with respect to motion are translated to higher forcing frequencies, and (c) at A/D = 1.0, no excitation region exists; the lift force is always dissipative.The flow-induced response of a flexibly mounted cylinder with attached wires is significantly altered as well, even far away from lock-in. Parameterizing the response using nominal reduced velocity Vrn = U/fnD, we found that frequency lock-in occurs and lift phase angles change through 180° at Vrn [thkap ] 4.9; anemometry in the wake confirms that a mode transition accompanies this premature lock-in. A plateau of constant response is established in the range Vrn = 5.1–6.0, reducing the peak amplitude moderately, and then vibrations are drastically reduced or eliminated above Vrn = 6.0. The vortex-induced vibration response of the cylinder with wires is extremely sensitive to angular bias near the critical value of Vrn = 6.0, and moderately so in the regime of suppressed vibration.

APA, Harvard, Vancouver, ISO, and other styles

35

Zhang, Xiulin, Xu Zhang, Shuni Zhou, Wenzha Yang, Liangbin Xu, Lina Yi, Gengqing Tian, Yong Ma, Yuheng Hao, and Wenchi Ni. "A Modified Wake Oscillator Model for the Cross-Flow Vortex-Induced Vibration of Rigid Cylinders with Low Mass and Damping Ratios." Journal of Marine Science and Engineering 11, no. 2 (January 17, 2023): 235. http://dx.doi.org/10.3390/jmse11020235.

Full text

Abstract:

The classical wake oscillator model is capable of predicting the vortex-induced vibration response of a cylinder at high mass-damping ratios, but it fails to perform satisfactorily at low mass-damping ratios. A modified wake oscillator model is presented in this paper. The modification method involves analyzing the variation law of the add mass coefficient of the cylinder versus reduced velocity and expressing the reference lift coefficient CL0 as a function of the add mass coefficient. The modified wake oscillator model has been demonstrated to have better accuracy in capturing maximum amplitudes and flow velocity at low mass-damping ratios. However, the modified model at present form is unable to accurately predict the vortex-induced vibration response at high damping ratios. The purpose of this paper is to propose a new modification idea. In order to achieve better results when applying this modification idea to particular objects, it may be necessary to first understand the response law of these kinds of objects.

APA, Harvard, Vancouver, ISO, and other styles

36

Wu, Chuan, Bo Yan, Guizao Huang, Bo Zhang, Zhongbin Lv, and Qing Li. "Wake-induced oscillation behaviour of twin bundle conductor transmission lines." Royal Society Open Science 5, no. 6 (June 2018): 180011. http://dx.doi.org/10.1098/rsos.180011.

Full text

Abstract:

A numerical method to simulate air flow around a bundle conductor line by means of the FLUENT software is presented and verified by a wind tunnel test for aerodynamic characteristics of a twin bundle conductor line. The lift and drag coefficients of the leeward sub-conductor of a twin bundle conductor varying with its relative position in the wake zone to the windward one under different wind velocities are numerically determined by the presented method. A user-defined subroutine of ABAQUS software is developed to apply the aerodynamic loads on each sub-conductor and the electromagnetic force between sub-conductors. The numerical simulation method for wake-induced oscillation of a bundle conductor line is proposed. By means of the numerical method, wake-induced oscillation processes of twin bundle conductor transmission lines under different parameters, including current intensity, spacer layout, span length and wind velocity, are numerically simulated. Moreover, the effects of those parameters on the oscillation characteristics of the lines, such as vibration mode, frequency, amplitude and motion trace, are discussed. The results obtained provide a fundamental basis for the understanding of wake-induced oscillation behaviour of twin bundle conductor transmission lines and the development of control technique for wake-induced oscillation.

APA, Harvard, Vancouver, ISO, and other styles

37

Cheng, Zhi, Fue-Sang Lien, Eugene Yee, and Ji Hao Zhang. "Mode transformation and interaction in vortex-induced vibration of laminar flow past a circular cylinder." Physics of Fluids 34, no. 3 (March 2022): 033607. http://dx.doi.org/10.1063/5.0080722.

Full text

Abstract:

An investigation of the mode transformation and interaction underlying the behavior of vortex-induced vibration (VIV) of a flow past a circular cylinder elastically mounted on a linear spring is conducted using a high-fidelity full-order model (FOM) based on computational fluid dynamics (CFD), a reduced-order model (ROM), and a dynamic mode decomposition (DMD) of the velocity. A reduced-order model for the fluid dynamics is obtained using the eigensystem realization algorithm (ERA), which is subsequently coupled to a linear structural equation to provide a state space model for the coupled VIV system, in order to provide a simplified computationally inexpensive mathematical representation of the system. This methodology is used to study the dynamics of laminar flows past an elastically mounted circular cylinder with Reynolds number Re ranging from 20 to 180, inclusive. The results of the simulations conducted using FOM/CFD and ROM/ERA, in conjunction with the power spectral analysis and DMD, are used to identify the characteristic natural frequencies and the growth/decay of various modes (including the complex interactions between the myriad wake modes and the structural mode) of the VIV system as a function of the Reynolds number and the reduced natural frequency Fs (or, equivalently, the reduced velocity Ur). A detailed analysis of the distribution of the eigenvalues of the transfer (or, system) matrix of the reduced VIV system shows that the frequency range of the lock-in can be partitioned into resonance and flutter lock-in regimes. The resonance lock-in (lower branch of the VIV response) dominates the fluid-structure interaction. Furthermore, it is shown that when the structural natural frequency is close to one of the eigenfrequencies associated with the wake modes, resonance lock-in (rather than flutter lock-in) will be the primary mechanism governing the VIV response even though the real part of the eigenvalues associated with structural mode is positive. With increasing Reynolds number, the instability of each wake mode is enhanced resulting in a transformation of the wake modes interacting with the structural mode. It is suggested herein that the weakened interaction between the wake modes and the structural mode at Re = 180 (associated with the greater separation between the root loci of the modes) results in the premature termination of the resonance lock-in at [Formula: see text] with increasing Ur. The DMD and power spectral analysis of the time series of the transverse displacement and lift coefficient are used to support the results obtained from ROM/ERA and, more specifically, to provide a clear demonstration of the balanced interaction between the wake modes and the structural mode. This result is used to explain the beating phenomenon, which occurs in the initial branch and the significant lag time that arises between the initial branch and the occurrence of a fully developed response in the lower branch.

APA, Harvard, Vancouver, ISO, and other styles

38

Li, Shouying, Chunyun Xiao, Teng Wu, and Zhengqing Chen. "Aerodynamic interference between the cables of the suspension bridge hanger." Advances in Structural Engineering 22, no. 7 (January 14, 2019): 1657–71. http://dx.doi.org/10.1177/1369433218820623.

Full text

Abstract:

The hangers of long-span suspension bridges are significantly prone to wind-induced vibrations due to their light mass, low frequency, and small structural damping. However, the underlying mechanism of the hanger vibration is not clearly clarified yet. To study the aerodynamic interference between the cables of the hanger, which is a possible mechanism for the hanger vibration, a series of wind tunnel tests were carried out to measure the mean aerodynamic drag and lift coefficients of a leeward cylinder. Then, the motion equations governing the vibration of leeward cable were derived based on the quasi-steady assumption. The numerical results show that large-amplitude vibrations of the leeward cable will occur in the region of 1 ≤ | Y| ≤ 3, where Y is a non-dimensional vertical coordinate normalized with the diameter of the cylinder. It appears that the stable trajectory of the leeward cable is ellipse, and trajectory is clockwise above the center line of the wake, whereas anti-clockwise below the center line of the wake. An important finding is that the frequency of the stable vibration of the leeward cable is slightly smaller than its natural frequency, which implies that a negative aerodynamic stiffness might arise. The time histories of the aerodynamic stiffness and damping forces on the leeward cable were identified from the numerical results. It seems that there is always a positive work done within a period by the aerodynamic stiffness force, whereas a negative work by the aerodynamic damping force. The response characteristics of the leeward cable of the hanger of suspension bridge obtained in this study are identical with those of the wake-induced flutter widely discussed for the power transmission line. This implies that wake-induced flutter theory could well illustrate the underlying mechanism of the aerodynamic interference effects on the hangers of a suspension bridge.

APA, Harvard, Vancouver, ISO, and other styles

39

A. Ferreira, L. G., C. C. Pagani Júnior, E. M. Gennaro, and C. De Marqui Junior. "A Numerical Study of a Rotor Induced Flow Based on a Finite-State Dynamic Wake Model." Trends in Computational and Applied Mathematics 22, no. 2 (June 28, 2021): 307–24. http://dx.doi.org/10.5540/tcam.2021.022.02.00307.

Full text

Abstract:

A Helicopter rotor undergoes unsteady aerodynamic loads ruled by the aeroelastic coupling between the elastic blades and the dynamic wake induced by rotary wings. Modeling the dynamic interaction between the structural and aerodynamic fields is a key point to understand aeroelastic phenomena associated with rotor stability, flow induced vibration and noise generation, among others. In this study, we address the Generalized Dynamic Wake Model, which describes the inflow velocity field at the rotor disk as a superposition of a finite number of induced flow states. It is a mature model that has been validated based on experimental data and numerically investigated from an eigenvalue problem formulation, whose eigenvalues and eigenvectors provide a deeper insight on the dynamic wake behavior. The paper extends the results presented in the literature to date in order to support physical interpretation of inflow states drawn from the finite-state wake model for flight conditions varying from hover to edgewise flight. The discussion of the wake model mathematical formulation is also oriented towards practical engineering applications to fill a gap in the literature.

APA, Harvard, Vancouver, ISO, and other styles

40

Fang, Chen, Zewen Wang, Haojun Tang, Yongle Li, and Zhouquan Deng. "Vortex-Induced Vibration of a Tall Bridge Tower with Four Columns and the Wake Effects on the Nearby Suspenders." International Journal of Structural Stability and Dynamics 20, no. 09 (August 2020): 2050105. http://dx.doi.org/10.1142/s0219455420501059.

Full text

Abstract:

With the increasing span of suspension bridges, the towers have higher heights and have become more flexible, and so do the nearby suspenders. Not only are the towers easy to be affected by winds, but also the nearby suspenders by the wake flow of the towers. To enhance the structural stiffness, a bridge tower may be designed with more columns, but this design may lead to strong aerodynamic interference among the columns, complicating the wind-induced behaviors of the tower and nearby suspenders. In this paper, wind tunnel tests and numerical simulations were carried out to investigate the vortex-induced vibration of a tall bridge tower with four columns, and the wake effects on nearby suspenders. The results show that the displacement response at the tower top increases with the increasing wind speed. No obvious lock-in region is observed, as different cross-sections of the tower show different vortex shedding characteristics. The vortex shedding characteristics are determined mainly by the aerodynamic forces acting on the leeward columns. In the wake of the tower, the aerodynamic forces of the suspenders have the same dominant frequencies as the shedding frequencies of the vortices from the tower. The frequencies may approach the natural frequencies of the suspenders, causing possible wake-induced vibration that should be avoided for a good design.

APA, Harvard, Vancouver, ISO, and other styles

41

Tsui, Y. T. "On wake-induced vibration of a conductor in the wake of another via a 3-D finite element method." Journal of Sound and Vibration 107, no. 1 (May 1986): 39–58. http://dx.doi.org/10.1016/0022-460x(86)90281-6.

Full text

APA, Harvard, Vancouver, ISO, and other styles

42

Lou, Min, Wu-gang Wu, and Peng Chen. "Experimental study on vortex induced vibration of risers with fairing considering wake interference." International Journal of Naval Architecture and Ocean Engineering 9, no. 2 (March 2017): 127–34. http://dx.doi.org/10.1016/j.ijnaoe.2016.08.006.

Full text

APA, Harvard, Vancouver, ISO, and other styles

43

Yao, W., and R. K. Jaiman. "Stability analysis of the wake-induced vibration of tandem circular and square cylinders." Nonlinear Dynamics 95, no. 1 (September 18, 2018): 13–28. http://dx.doi.org/10.1007/s11071-018-4547-9.

Full text

APA, Harvard, Vancouver, ISO, and other styles

44

Assi, Gustavo R. S. "Wake-induced vibration of tandem and staggered cylinders with two degrees of freedom." Journal of Fluids and Structures 50 (October 2014): 340–57. http://dx.doi.org/10.1016/j.jfluidstructs.2014.07.002.

Full text

APA, Harvard, Vancouver, ISO, and other styles

45

Farshidianfar, A., and N. Dolatabadi. "Modified higher-order wake oscillator model for vortex-induced vibration of circular cylinders." Acta Mechanica 224, no. 7 (February 12, 2013): 1441–56. http://dx.doi.org/10.1007/s00707-013-0819-0.

Full text

APA, Harvard, Vancouver, ISO, and other styles

46

Rajamuni, Methma M., Mark C. Thompson, and Kerry Hourigan. "Transverse flow-induced vibrations of a sphere." Journal of Fluid Mechanics 837 (January 5, 2018): 931–66. http://dx.doi.org/10.1017/jfm.2017.881.

Full text

Abstract:

Flow-induced vibration of an elastically mounted sphere was investigated computationally for the classic case where the sphere motion was constrained to move in a direction transverse to the free stream. This study, therefore, provides additional insight into, and comparison with, corresponding experimental studies of transverse motion, and distinction from numerical and experimental studies with specific constraints such as tethering (Williamson & Govardhan, J. Fluids Struct., vol. 11, 1997, pp. 293–305) or motion in all three directions (Behara et al., J. Fluid Mech., vol. 686, 2011, pp. 426–450). Two sets of simulations were conducted by fixing the Reynolds number at $Re=300$ or 800 over the reduced velocity ranges $3.5\leqslant U^{\ast }\leqslant 100$ and $3\leqslant U^{\ast }\leqslant 50$ respectively. The reduced mass of the sphere was kept constant at $m_{r}=1.5$ for both sets. The flow satisfied the incompressible Navier–Stokes equations, while the coupled sphere motion was modelled by a spring–mass–damper system, with damping set to zero. The sphere showed a highly periodic large-amplitude vortex-induced vibration response over a lower reduced velocity range at both Reynolds numbers considered. This response was designated as branch A, rather than the initial/upper or mode I/II branch, in order to allow it to be discussed independently from the observed experimental response at higher Reynolds numbers which shows both similarities and differences. At $Re=300$, it occurred over the range $5.5\leqslant U^{\ast }\leqslant 10$, with a maximum oscillation amplitude of ${\approx}0.4D$. On increasing the Reynolds number to 800, this branch widened to cover the range $4.5\leqslant U^{\ast }\leqslant 13$ and the oscillation amplitude increased (maximum amplitude ${\approx}0.6D$). In terms of wake dynamics, within this response branch, two streets of interlaced hairpin-type vortex loops were formed behind the sphere. The upper and lower sets of vortex loops were disconnected, as were their accompanying tails. The wake maintained symmetry relative to the plane defined by the streamwise and sphere motion directions. The topology of this wake structure was analogous to that seen experimentally at higher Reynolds numbers by Govardhan & Williamson (J. Fluid Mech., vol. 531, 2005, pp. 11–47). At even higher reduced velocities, the sphere showed distinct oscillatory behaviour at both Reynolds numbers examined. At $Re=300$, small but non-negligible oscillations were found to occur (amplitude of ${\approx}0.05D$) within the reduced velocity ranges $13\leqslant U^{\ast }\leqslant 16$ and $26\leqslant U^{\ast }\leqslant 100$, named branch B and branch C respectively. Moreover, within these reduced velocity ranges, the centre of motion of the sphere shifted from its static position. In contrast, at $Re=800$, the sphere showed an aperiodic intermittent mode IV vibration state immediately beyond branch A, for $U^{\ast }\geqslant 14$. This vibration state was designated as the intermittent branch. Interestingly, the dominant frequency of the sphere vibration was close to the natural frequency of the system, as observed by Jauvtis et al. (J. Fluids Struct., vol. 15(3), 2001, pp. 555–563) in higher-mass-ratio higher-Reynolds-number experiments. The oscillation amplitude increased as the reduced velocity increased and reached a value of ${\approx}0.9D$ at $U^{\ast }=50$. The wake was irregular, with multiple vortex shedding cycles during each cycle of sphere oscillation.

APA, Harvard, Vancouver, ISO, and other styles

47

Rasani, Mohammad Rasidi, Hazim Moria, Michael Beer, and Ahmad Kamal Ariffin. "Vibration Performance of a Flow Energy Converter behind Two Side-by-Side Cylinders." Journal of Marine Science and Engineering 7, no. 12 (November 29, 2019): 435. http://dx.doi.org/10.3390/jmse7120435.

Full text

Abstract:

Flow-induced vibrations of a flexible cantilever plate, placed in various positions behind two side-by-side cylinders, were computationally investigated to determine optimal location for wake-excited energy harvesters. In the present study, the cylinders of equal diameter D were fixed at center-to-center gap ratio of T / D = 1 . 7 and immersed in sub-critical flow of Reynold number R e D = 10 , 000 . A three-dimensional Navier–Stokes flow solver in an Arbitrary Lagrangian–Eulerian (ALE) description was closely coupled to a non-linear finite element structural solver that was used to model the dynamics of a composite piezoelectric plate. The cantilever plate was fixed at several positions between 0 . 5 < x / D < 1 . 5 and - 0 . 85 < y / D < 0 . 85 measured from the center gap between cylinders, and their flow-induced oscillations were compiled and analyzed. The results indicate that flexible plates located at the centerline between the cylinder pairs experience the lowest mean amplitude of oscillation. Maximum overall amplitude in oscillation is predicted when flexible plates are located in the intermediate off-center region downstream of both cylinders. Present findings indicate potential to further maximize wake-induced energy harvesting plates by exploiting their favorable positioning in the wake region behind two side-by-side cylinders.

APA, Harvard, Vancouver, ISO, and other styles

48

Bourguet, Rémi, and Michael S. Triantafyllou. "The onset of vortex-induced vibrations of a flexible cylinder at large inclination angle." Journal of Fluid Mechanics 809 (November 9, 2016): 111–34. http://dx.doi.org/10.1017/jfm.2016.657.

Full text

Abstract:

The onset of the vortex-induced vibration (VIV) regime of a flexible cylinder inclined at$80^{\circ }$within a uniform current is studied by means of direct numerical simulations, at Reynolds number$500$based on the body diameter and inflow velocity magnitude. A range of values of the reduced velocity, defined as the inverse of the fundamental natural frequency, is examined in order to capture the emergence of the body responses and explore the concomitant reorganization of the flow and fluid forcing. Additional simulations at normal incidence confirm that the independence principle, which states that the system behaviour is determined by the normal inflow component, does not apply at such large inclination angle. Contrary to the normal incidence case, the free vibrations of the inclined cylinder arise far from the Strouhal frequency, i.e. the vortex shedding frequency downstream of a fixed rigid cylinder. The trace of the stationary body wake is found to persist beyond the vibration onset: the flow may still exhibit an oblique component that relates to the slanted vortex shedding pattern observed in the absence of vibration. This flow component which occurs close to the Strouhal frequency, at a high and incommensurable frequency compared to the vibration frequency, is referred to as Strouhal component; it induces a high-frequency component in fluid forcing. The vibration onset is accompanied by the appearance of novel, low-frequency components of the flow and fluid forcing which are synchronized with body motion. This second dominant flow component, referred to as lock-in component, is characterized by a parallel spatial pattern. The Strouhal and lock-in components of the flow coexist over a range of reduced velocities, with variable contributions, which results in a variety of mixed wake patterns. The transition from oblique to parallel vortex shedding that occurs during the amplification of the structural responses, is driven by the opposite trends of these two component contributions: the decrease of the Strouhal component magnitude associated with the progressive disappearance of the high-frequency force component, and simultaneously, the increase of the lock-in component magnitude, which dominates once the fully developed VIV regime is reached and the flow dynamics is entirely governed by wake–body synchronization.

APA, Harvard, Vancouver, ISO, and other styles

49

Rajamuni, Methma M., Mark C. Thompson, and Kerry Hourigan. "Vortex-induced vibration of a transversely rotating sphere." Journal of Fluid Mechanics 847 (May 29, 2018): 786–820. http://dx.doi.org/10.1017/jfm.2018.309.

Full text

Abstract:

The effects of transverse rotation on the vortex-induced vibration (VIV) of a sphere in a uniform flow are investigated numerically. The one degree-of-freedom sphere motion is constrained to the cross-stream direction, with the rotation axis orthogonal to flow and vibration directions. For the current simulations, the Reynolds number of the flow, $Re=UD/\unicode[STIX]{x1D708}$, and the mass ratio of the sphere, $m^{\ast }=\unicode[STIX]{x1D70C}_{s}/\unicode[STIX]{x1D70C}_{f}$, were fixed at 300 and 2.865, respectively, while the reduced velocity of the flow was varied over the range $3.5\leqslant U^{\ast }~(\equiv U/(f_{n}D))\leqslant 11$, where, $U$ is the upstream velocity of the flow, $D$ is the sphere diameter, $\unicode[STIX]{x1D708}$ is the fluid viscosity, $f_{n}$ is the system natural frequency and $\unicode[STIX]{x1D70C}_{s}$ and $\unicode[STIX]{x1D70C}_{f}$ are solid and fluid densities, respectively. The effect of sphere rotation on VIV was studied over a wide range of non-dimensional rotation rates: $0\leqslant \unicode[STIX]{x1D6FC}~(\equiv \unicode[STIX]{x1D714}D/(2U))\leqslant 2.5$, with $\unicode[STIX]{x1D714}$ the angular velocity. The flow satisfied the incompressible Navier–Stokes equations while the coupled sphere motion was modelled by a spring–mass–damper system, under zero damping. For zero rotation, the sphere oscillated symmetrically through its initial position with a maximum amplitude of approximately 0.4 diameters. Under forced rotation, it oscillated about a new time-mean position. Rotation also resulted in a decreased oscillation amplitude and a narrowed synchronisation range. VIV was suppressed completely for $\unicode[STIX]{x1D6FC}>1.3$. Within the $U^{\ast }$ synchronisation range for each rotation rate, the drag force coefficient increased while the lift force coefficient decreased from their respective pre-oscillatory values. The increment of the drag force coefficient and the decrement of the lift force coefficient reduced with increasing reduced velocity as well as with increasing rotation rate. In terms of wake dynamics, in the synchronisation range at zero rotation, two equal-strength trails of interlaced hairpin-type vortex loops were formed behind the sphere. Under rotation, the streamwise vorticity trail on the advancing side of the sphere became stronger than the trail in the retreating side, consistent with wake deflection due to the Magnus effect. This symmetry breaking appears to be associated with the reduction in the observed amplitude response and the narrowing of the synchronisation range. In terms of variation with Reynolds number, the sphere oscillation amplitude was found to increase over the range $Re\in [300,1200]$ at $U^{\ast }=6$ for each of $\unicode[STIX]{x1D6FC}=0.15$, 0.75 and 1.5. The VIV response depends strongly on Reynolds number, with predictions indicating that VIV will persist for higher rotation rates at higher Reynolds numbers.

APA, Harvard, Vancouver, ISO, and other styles

50

Bourguet, Rémi, and David Lo Jacono. "In-line flow-induced vibrations of a rotating cylinder." Journal of Fluid Mechanics 781 (September 16, 2015): 127–65. http://dx.doi.org/10.1017/jfm.2015.477.

Full text

Abstract:

The flow-induced vibrations of an elastically mounted circular cylinder, free to oscillate in the direction parallel to the current and subjected to a forced rotation about its axis, are investigated by means of two- and three-dimensional numerical simulations, at a Reynolds number equal to 100 based on the cylinder diameter and inflow velocity. The cylinder is found to oscillate up to a rotation rate (ratio between the cylinder surface and inflow velocities) close to 2 (first vibration region), then the body and the flow are steady until a rotation rate close to 2.7 where a second vibration region begins. Each vibration region is characterized by a specific regime of response. In the first region, the vibration amplitude follows a bell-shaped evolution as a function of the reduced velocity (inverse of the oscillator natural frequency). The maximum vibration amplitudes, even though considerably augmented by the rotation relative to the non-rotating body case, remain lower than 0.1 cylinder diameters. Due to their trends as functions of the reduced velocity and to the fact that they develop under a condition of wake-body synchronization or lock-in, the responses of the rotating cylinder in this region are comparable to the vortex-induced vibrations previously described in the absence of rotation. The symmetry breaking due to the rotation is shown to directly impact the structure displacement and fluid force frequency contents. In the second region, the vibration amplitude tends to increase unboundedly with the reduced velocity. It may become very large, higher than 2.5 diameters in the parameter space under study. Such structural oscillations resemble the galloping responses reported for non-axisymmetric bodies. They are accompanied by a dramatic amplification of the fluid forces compared to the non-vibrating cylinder case. It is shown that body oscillation and flow unsteadiness remain synchronized and that a variety of wake topologies may be encountered in this vibration region. The low-frequency, large-amplitude responses are associated with novel asymmetric multi-vortex patterns, combining a pair and a triplet or a quartet of vortices per cycle. The flow is found to undergo three-dimensional transition in the second vibration region, with a limited influence on the system behaviour. It appears that the transition occurs for a substantially lower rotation rate than for a rigidly mounted cylinder.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Wake Induced Vibration (WIV)'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles