VORTEX-INDUCED VIBRATIONS MODEL WITH 2 DEGREES OF FREEDOM OF RIGID CYLINDERS NEAR A FIXED WALL BASED ON WAKE OSCILLATOR

2021 ◽  
pp. 56-66
Author(s):  
Rafael Fehér ◽  
Juan Pablo Julca Avila
Keyword(s):  
Degrees Of Freedom ◽  
Wake Oscillator ◽  
Vortex Induced Vibrations

scholarly journals Optimal energy harvesting from vortex-induced vibrations of cables

2016 ◽  
Vol 472 (2195) ◽  
pp. 20160583 ◽  
Author(s):  
G. O. Antoine ◽  
E. de Langre ◽  
S. Michelin
Keyword(s):  
Energy Harvesting ◽  
Flow Velocity ◽  
Passive Control ◽  
Optimal Harvesting ◽  
Control Mechanisms ◽  
Wake Oscillator ◽  
Vortex Induced Vibrations ◽  
Harvesting Systems ◽  
Gradient Based ◽  
Flexible Cables

Vortex-induced vibrations (VIV) of flexible cables are an example of flow-induced vibrations that can act as energy harvesting systems by converting energy associated with the spontaneous cable motion into electricity. This work investigates the optimal positioning of the harvesting devices along the cable, using numerical simulations with a wake oscillator model to describe the unsteady flow forcing. Using classical gradient-based optimization, the optimal harvesting strategy is determined for the generic configuration of a flexible cable fixed at both ends, including the effect of flow forces and gravity on the cable’s geometry. The optimal strategy is found to consist systematically in a concentration of the harvesting devices at one of the cable’s ends, relying on deformation waves along the cable to carry the energy towards this harvesting site. Furthermore, we show that the performance of systems based on VIV of flexible cables is significantly more robust to flow velocity variations, in comparison with a rigid cylinder device. This results from two passive control mechanisms inherent to the cable geometry: (i) the adaptability to the flow velocity of the fundamental frequencies of cables through the flow-induced tension and (ii) the selection of successive vibration modes by the flow velocity for cables with gravity-induced tension.

Three-dimensional vortex-induced vibrations of a circular cylinder predicted using a wake oscillator model

2021 ◽  
Vol 80 ◽  
pp. 103078
Author(s):  
Yun Gao ◽  
Zhuangzhuang Zhang ◽  
Ganghui Pan ◽  
Geng Peng ◽  
Lei Liu ◽  
...  
Keyword(s):  
Circular Cylinder ◽  
Three Dimensional ◽  
Oscillator Model ◽  
Wake Oscillator Model ◽  
Wake Oscillator ◽  
Vortex Induced Vibrations

The Numerical Research of Two-Degrees-of-Freedom Vortex-Induced Vibrations of Circular Cylinders

2012 ◽  
Vol 204-208 ◽  
pp. 4598-4601
Author(s):  
Jie Li Fan ◽  
Wei Ping Huang
Keyword(s):  
Degrees Of Freedom ◽  
Amplitude Ratio ◽  
Flow Direction ◽  
Cross Flow ◽  
Circular Cylinders ◽  
Two Degrees Of Freedom ◽  
Line Frequency ◽  
Ansys Cfx ◽  
Vortex Induced Vibrations ◽  
Lock In

The two-degrees-of-freedom of vortex-induced vibration of circular cylinders is numerically simulated with the software ANSYS/CFX. The VIV characteristic, in the two different conditions (A/D=0.07 and A/D=1.0), is analyzed. When A/D is around 0.07, the amplitude ratio of the cylinder’s VIV between in-line and cross-flow direction in the lock-in is lower than that in the lock-out. The in-line frequency is twice of that in cross-flow direction in the lock-out, but in the lock-in, it is the same as that in cross-flow direction and the same as that of lift force. When A/D is around 1.0, the amplitude ratio of the VIV between in-line and cross-flow in the lock-in is obviously larger than that in the lock-out. Both in the lock-in and in the lock-out, the in-line frequency is twice of that in cross-flow direction.

POD Analysis of the Wake Development of a Pivoted Circular Cylinder Undergoing Vortex Induced Vibrations

2017 ◽  
Author(s):  
E. Marble ◽  
C. Morton ◽  
S. Yarusevych
Keyword(s):  
Circular Cylinder ◽  
Degrees Of Freedom ◽  
Structural Response ◽  
Cylinder Wake ◽  
Time Resolved ◽  
Vortex Induced Vibrations ◽  
Image Velocimetry ◽  
Pod Analysis ◽  
Component Particle ◽  
Proper Orthogonal

Vortex Induced Vibrations (VIV) of a pivoted circular cylinder with two degrees of freedom are investigated experimentally, focusing on quantifying the wake topology. Experiments are performed in a water tunnel for a pivoted cylinder with a fixed mass ratio of 10.8, moment of inertia ratio of 87.0–109.5, and a diameter-based Reynolds number of 3100. The reduced velocity was varied from 4.42 to 9.05 by varying the natural frequency of the structure. Velocity measurements were performed via time-resolved, two-component Particle Image Velocimetry (PIV), synchronized with cylinder displacement measurements. Time and phase-averaging are employed to analyze the wake development and relate it to the structural response. Proper Orthogonal Decomposition (POD) is utilized to gain insight into the development of coherent structures in the cylinder wake. The observed shedding patterns agree well with the Morse & Williamson [1] shedding map except for the cases at the boundary between 2P and non-synchronized shedding. The results show that the cylinder follows an elliptical trajectory with equal frequency of oscillation in streamwise and transverse directions. For the 2P regime, the tilt and direction of trajectory affect the formation and development of vortices in the wake. This results in a distinct asymmetry about the wake centerline in time-averaged statistics.

scholarly journals Optimal Energy Harvesting From Vortex-Induced Vibrations of Cables

2016 ◽  
Author(s):  
Guillaume O. Antoine ◽  
Sébastien Michelin ◽  
Emmanuel de Langre
Keyword(s):  
Energy Harvesting ◽  
Equation Of Motion ◽  
Complex Geometries ◽  
Wake Oscillator ◽  
Flow Fluctuations ◽  
Rigid Rods ◽  
Vortex Induced Vibrations ◽  
Numerical Tools ◽  
Carry Over ◽  
Flexible Cables

We propose to use flexible cables instead of rigid rods in devices extracting energy from Vortex-Induced Vibrations (VIVs). We use a linear equation of motion for the structure coupled with a nonlinear wake oscillator and numerical tools to simulate the VIVs of hanging strings/cables. While extracting energy from the VIVs of a straight cable with a harvester attached to one of its ends is as efficient as extracting energy from the VIVs of rigid structures, we find that the former is much more robust to flow fluctuations than the latter. We finally show that those results carry over to more complex geometries (e.g. catenary).

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