Enhancement of flow-induced motion of rigid circular cylinder on springs by localized surface roughness at 3×104≤Re≤1.2×105

Park, Hongrae; Kumar, R. Ajith; Bernitsas, Michael M.

doi:10.1016/j.oceaneng.2013.06.026

Cited by 111 publications

(74 citation statements)

References 29 publications

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“…In Park's [26] research, the SG and HG responses of the circular cylinder combined with PTC were observed at different levels of surface roughness. In Zhang's research [28], two HG (HG1 and HG2) responses of triangular prism were observed due to the difference in system damping.…”

Section: Results Of Oscillation Mode Under Different Parametersmentioning

confidence: 99%

Experimental Investigation on Soft Galloping and Hard Galloping of Triangular Prisms

et al. 2017

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Abstract:The studies currently on soft galloping (SG) and hard galloping (HG) are scarce. In this study, SG and HG of spring-mounted triangular prisms in a water channel are investigated experimentally. A power take-off system (PTO), a spring system, additional weights, and different triangular prisms were used to achieve the variations in damping coefficient c, system stiffness K, oscillation mass m and section aspect ratios α, respectively. The present paper proves that the VIV (vortex-induced vibration) lower branch can be observed in the SG response. In SG response, VIV branches are incomplete while the galloping branch is complete, and galloping can be self-initiated only in the self-excited region. On the contrary, in HG response, VIV branches are complete, the galloping branch is incomplete, and galloping can only be initiated by external excitation at a velocity exceeding the critical velocity. As c and m increase, or K and α decrease, the oscillation mode of a triangular prism gradually transitions from SG to CG (critical galloping), and continues to HG. The amplitude in VIV branch is the main reason causing the onset of galloping in SG response. A critical damping coefficient c c , which is dependent on m, K and α, is proposed to predict the occurrences of SG, CG and HG. When c < c c , SG occurs; when c > c c , HG occurs; when c = c c , CG occurs.

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Section: Results Of Oscillation Mode Under Different Parametersmentioning

confidence: 99%

Experimental Investigation on Soft Galloping and Hard Galloping of Triangular Prisms

et al. 2017

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“…The VIV of the prism is driven by the imposed lift on the body from vortex shedding [1]. In the transition branch from VIV to galloping, f* declines sharply due to the coexistence of the driving mechanisms of oscillatory lift due to vortex shedding and instability inducing oscillatory lift due to shear layer motion in this transition region [6,11,12,21,22], and A*continues to increase with increasing Ur. As the prism response is in galloping branch, f* levels off at low values, and A* still exhibits an increasing trend.…”

Section: Amplitude and Frequency Responsesmentioning

confidence: 99%

“…Besides, the galloping of the prism presents, in turn, the soft galloping (SG), the hard galloping 1 (HG1), and the hard galloping 2 (HG2) with increasing ζ total . Soft galloping is defined as the self-initiated galloping, while hard galloping requires an externally imposed initial threshold amplitude [12]. The amplitude and frequency characteristics of the equilateral triangle prism for each ζ total are summarized as follows:…”

Section: Amplitude and Frequency Responsesmentioning

confidence: 99%

“…Besides, this device satisfies all of the requirements set by the California Energy Commission and the U.S. DOE [9]. In order to convert more hydrokinetic energy to mechanical energy and subsequently to electrical energy over broader velocity range, Chang et al [11], Park et al [12] and Ding [13] tried to enhance the FIV of the circular cylinder by altering the cylinder surface roughness with the help of Passive Turbulence Control (PTC). The maximum energy conversion efficiency was increased from 22% [10] to 28% [13].…”

Section: Introductionmentioning

confidence: 99%

“…The oscillation response of the prism is in the VIV desynchronization branch where f * is more than 1 indicating the response frequency of the prism is higher than the nature frequency of the vibration system in air. When the prism is given a threshold initial displacement of approximately 1.5D at U r = 9.07, the prism enters into HG1 where the oscillation response jumps to the galloping branch from the VIV upper branch [12]. This threshold amplitude is given to the prism by manually pushing the prism.…”

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confidence: 99%

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Flow Induced Vibration and Energy Extraction of an Equilateral Triangle Prism at Different System Damping Ratios

et al. 2016

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Abstract:The flow induced vibration and energy extraction of an equilateral triangle prism elastically mounted in a water channel are investigated experimentally at different system damping ratios ζ total with the constant oscillating mass M osc and system stiffness K. A power take-off system with a variable damping function is developed. The translation-rotation equation of the vibration system deduced in the study indicates that the total oscillating mass includes the material mass, and the equivalent mass due to the rotation of the gears and rotor. Besides, increasing load resistance can result in a decrease in ζ total when K and M osc remain unchanged. The prism experiences, in turn, soft galloping, hard galloping 1 and hard galloping 2 with increasing ζ total . As ζ total increases up to 0.335, only the vortex-induced vibration is observed because the extremely high ζ total prevents the prism from galloping. The response amplitude decreases with the increasing ζ total . In addition, higher ζ total promotes the galloping to start at a higher reduced velocity. The galloping characteristics of the prism, including large amplitude responses in an extremely large range of flow velocities, excellent vibration stationarity, and steady vibration frequencies, are beneficial for improving energy conversion. The prism can extract hydraulic energy for the flow velocity U > 0.610 m/s. The harnessed power P out and the energy conversion efficiency η out increase with increasing ζ total in the galloping zone. The maximum P out and η out reach 53.56 W and 40.44%, respectively. The optimal system damping ratio for extracting energy is the maximum system damping ratio that the prism can overcome to experience stable galloping.

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Hydrokinetic Energy Conversion Using a Single-Cylinder Nonlinear Oscillator in Flow Induced Oscillations

Bernitsas

Sun

2021

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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Enhancement of flow-induced motion of rigid circular cylinder on springs by localized surface roughness at 3×104≤Re≤1.2×105

Cited by 111 publications

References 29 publications

Experimental Investigation on Soft Galloping and Hard Galloping of Triangular Prisms

Experimental Investigation on Soft Galloping and Hard Galloping of Triangular Prisms

Flow Induced Vibration and Energy Extraction of an Equilateral Triangle Prism at Different System Damping Ratios

Hydrokinetic Energy Conversion Using a Single-Cylinder Nonlinear Oscillator in Flow Induced Oscillations

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