Design considerations for a three-tethered point absorber wave energy converter with nonlinear coupling between hydrodynamic modes

Tran, N.; Sergiienko, Nataliia Y.; Cazzolato, B.; Ghayesh, Mergen H.; Arjomandi, Maziar

doi:10.1016/j.oceaneng.2022.111351

Cited by 7 publications

(3 citation statements)

References 33 publications

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“…where other modes of motion are included and the model is forced by incident waves. Recent work on submerged wave energy convertors (Tran et al., 2021; Tran, Sergiienko, Cazzolato, Ghayesh, & Arjomandi, 2022) suggests that mode coupling is of high importance in power absorption – there would be great value in extending the weakly nonlinear model used in these works to a hybrid model taking better account of shallow water effects. However, this requires further model development and validation experiments.…”

Section: Discussionmentioning

confidence: 99%

Hybrid axisymmetric model for forced heave of a shallowly submerged cylindrical wave energy converter

McCauley,

Wolgamot,

Draper

et al. 2023

Flow

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Shallowly submerged oscillating structures may be found in wave energy devices or semi-submersible vessels. Predicting the force on such structures is critical for design purposes, but complicated due to nonlinear phenomena which can occur in shallow water, including wave breaking and bore formation. Such effects are particularly important around the first ‘resonance’ frequency of the fluid on top of the device, where linear theory predicts large flows on/off the cylinder and corresponding surface elevations and forces. In an effort to create a reliable and efficient model to predict the hydrodynamic force on a shallowly submerged truncated vertical cylinder, an axisymmetric nonlinear hybrid model is developed for forced heave oscillations. The flow above the cylinder is modelled using the nonlinear shallow water equations, and linear potential flow theory is used in the surrounding fluid. The model is compared with experimental results for forced heave oscillations and performs well for predicting the heave force. It is then used to examine linearised heave force for increasing amplitudes of (prescribed) harmonic heave motion. There is a significant reduction in the peaks of radiation damping and added mass coefficients with increasing amplitude, and associated shifts in the frequencies of the peaks.

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Section: Discussionmentioning

confidence: 99%

Hybrid axisymmetric model for forced heave of a shallowly submerged cylindrical wave energy converter

McCauley,

Wolgamot,

Draper

et al. 2023

Flow

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show abstract

“…The impact of pitch on the power extraction capabilities of a submerged cylindrical WEC with a radius of 12.5 m and a height of 5 m using a weak-scatterer model was studied in [10]. The authors considered linear and nonlinear potential theories for water and submergence depths of 6.5 and 30 m. The results show that using the nonlinear theory improves the WEC performance due to more stable pitch adjustments, resulting in better power absorption.…”

Section: Introductionmentioning

confidence: 99%

A Numerical Study of the Performance of Point Absorber Wave Energy Converters

Rathaur,

Verdin,

Ghosh

2024

Applied Sciences

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Free-floating and submerged wave energy converters (SWECs) are regarded as promising technologies for renewable energy production. These converters rely on a heave-motion buoy to capture the kinetic energy of ocean waves and convert it into electrical energy through power conversion systems. To better understand the impact of various factors on power generation and efficiency, the effects of different buoy shapes (rectangular, circular cylinder, and trapezoidal fin), submergence depths (0, 0.1, and 0.2 m), wave heights (0.04, 0.06, and 0.1 m), and spring stiffness (50 and 100 N/m) were investigated. A 2D numerical wave tank with a buoy was simulated, and the results were validated against experimental data. Information on vorticity, vertical displacement, power absorption, and efficiency are provided. The findings indicate that the buoy shape and wave height significantly affect power absorption and efficiency. Additionally, this study reveals that increasing submergence leads to higher power absorption and lower conversion efficiency.

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“…Regarding the harmonic hydrodynamics of point-absorber wave-energy converters (PA-WECs), previous results have revealed their significant role in wave elevation and motion responses. Tran et al [5] discovered that geometric nonlinearities lead to sub-harmonic excitations that severely compromise device performance. Yang et al [6] observed a significant contribution from the harmonic component of wave elevation and noted that this component increases performance under stationary waves around WECs.…”

Section: Introductionmentioning

confidence: 99%

Experimental and CFD Assessment of Harmonic Characteristics of Point-Absorber Wave-Energy Converters with Nonlinear Power Take-Off System

Yi,

Sun,

Liu

et al. 2023

JMSE

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The wave-energy excitation of point absorbers is highly associated with their resonant movement, and harmonic characteristics are of increasing concern in affecting resonance. However, the commonly used linearized power take-off (PTO) systems underestimate the impact of harmonics. The purpose of this study is to address the knowledge gap in assessing the contribution of hydraulic PTO systems to higher harmonic wave loads and velocities. In the present work, higher harmonics in point-absorber wave-energy converters (PA-WECs) with hydraulic power take-off (PTO) systems are investigated through both experimental and computational fluid dynamics (CFD) methods. The fast Fourier transform is used to decompose the high-order harmonics. To account for the influence of nonlinear wave–wave interaction on harmonics, the isolated PA-WEC is used as a basis for comparison with the paired PA-WECs. The influence of wave steepness is also estimated at two resonance periods. Results indicate that the additional resonance of the paired PA-WECs may be attributed to the harmonic wave loads at longer wave periods. Harmonic wave loads of paired PA-WECs typically have a more substantial impact and increase more rapidly with increasing wave steepness compared to isolated PA-WECs. Furthermore, as the wave steepness increases, there are significant enhancements in both the harmonic wave loads and heaving velocity, which strongly correlate with the instantaneous maximum hydraulic power. Consequently, our study will contribute to enhancing the maximum power output in the design of future point absorber arrays.

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Design considerations for a three-tethered point absorber wave energy converter with nonlinear coupling between hydrodynamic modes

Cited by 7 publications

References 33 publications

Hybrid axisymmetric model for forced heave of a shallowly submerged cylindrical wave energy converter

Hybrid axisymmetric model for forced heave of a shallowly submerged cylindrical wave energy converter

A Numerical Study of the Performance of Point Absorber Wave Energy Converters

Experimental and CFD Assessment of Harmonic Characteristics of Point-Absorber Wave-Energy Converters with Nonlinear Power Take-Off System

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