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A plate‐wave energy converter (pWEC) moored in front of a floating stationary breakwater is considered. The pWEC is composed of a submerged flexible plate with piezoelectric layers bonded to both faces of it. Hence the elastic motion of the plate excited by water waves can be transformed into useful electricity due to the piezoelectric effect. To evaluate the performance of the breakwater‐attached pWEC in terms of wave power absorption and wave attenuation, a hydroelastic model based on linear potential flow theory and the eigenfunction matching method is developed with the electromechanical and the hydrodynamic problems of the pWEC coupled together. The pWEC can be either simply supported or clamped at the edge. A multi‐parameter analysis is carried out with the employment of the present model. Effects of the width, submergence and edge types of the plate, together with the scales of the breakwater, including its width and draft, on wave power absorption and wave attenuation, are examined. As the pWEC moves towards a deeper position, the main peaks of the frequency response of the wave power absorption efficiency become lower and narrower. In contrast, its effect on wave attenuation is limited. [ABSTRACT FROM AUTHOR]

We present an analysis of wave energy devices with air-filled compressible submerged volumes, where variability of volume is achieved by means of a horizontal surface free to move up and down relative to the body. An analysis of bodies without power takeoff (PTO) systems is first presented to demonstrate the positive effects a compressible volume could have on the body response. Subsequently, two compressible device variations are analysed. In the first variation, the compressible volume is connected to a fixed volume via an air turbine for PTO. In the second variation, a water column separates the compressible volume from another volume, which is fitted with an air turbine open to the atmosphere. Both floating and bottom-fixed, axisymmetric, configurations are considered, and linear analysis is employed throughout. Advantages and disadvantages of each device are examined in detail. Some configurations with displaced volumes less than 2000m³ and with constant turbine coefficients are shown to be capable of achieving 80% of the theoretical maximum absorbed power over a wave period range of about 4 s. [ABSTRACT FROM AUTHOR]

Abstract: A numerical method based on a two-phase level set with the global mass correction and immersed boundary method is developed here to simulate wave interaction with a semi-submerged chamber. An oscillating water column, where power is extracted due to a normally incident wave forcing the free surface of the fluid between the front wall and rear wall to oscillate, is studied numerically to examine its hydrodynamic characteristics. The numerical results for an OWC under various wave conditions are compared with published experimental data by Morris-Thomas et al. [Morris-Thomas TM, Irvin RJ, Thiagarajan KP. An investigation into the hydrodynamic efficiency of an oscillating water column. J Offshore Mech Arct Eng 2007;129:273–8] and theory by Evans and Porter [Evans DV, Porter R. Hydrodynamic characteristics of an oscillating water column device. Appl Ocean Res 1995;17:155–64]. The flow field, free surface and pressure distribution are presented at different instants in time to reveal the energy loss clearly. The hydrodynamic efficiency predicted by the numerical results demonstrates a banded efficiency centred about a resonant peak and agrees with the physical experiment more closely than with the inviscid linear theory. The effect of the various wave conditions, immersion depth, thickness of the front wall of the chamber, vortex generation around the front wall in the water and air chamber characteristics on the efficiency of wave energy extraction from the OWC is investigated. [Copyright &y& Elsevier]

Integrating wave energy converters with marine structures such as breakwaters, piles, and offshore wind turbines offers benefits in terms of wave power extraction, construction costs, and survivability. In this paper, the integration of an oscillating water column(OWC) into a vertical tubular structure is considered. The OWC chamber is enclosed by the tubular-structure with its submerged side partially open to the sea. As ocean waves propagate through the device, an air turbine installed at the top of the chamber can be driven to extract wave power. An analytical model based on potential flow theory and the eigen-function matching method is developed to solve the wave scattering and radiation problems of the device in finite water depths. Wave excitation volume flux, hydrodynamic coefficients, optimal turbine damping and power capture factor are evaluated. Upon successful validation, the model is applied to investigate the effect of the radius and finite wall thickness of the tubular-structure, the size and position of the opening on wave power extraction. We find that a thinner chamber wall thickness offers benefits to wave power extraction in terms of a broader primary band of power capture factor response, and that a broader and higher capture factor band can be achieved by increasing the height of the vertical opening. • We develop an analytical model to study an OWC integrated into a tubular structure. • The OWC lateral opening can be applied at any position beneath the mean water level. • The new analytical model eliminates the need for the thin wall assumption. • The small wall thickness of the chamber offers benefits for wave power extraction. • Increasing height of the opening leads to a broader efficiency band. [ABSTRACT FROM AUTHOR]

Oscillating Water Columns (OWCs) are some of the most-studied wave energy converters (WECs). Previous work showed that the geometric characteristics of the OWC can play a significant role in the efficiency of the device. In this study, we investigate the behaviour of different designs of OWC making geometric modifications to the classic design of OWC and the U-OWC, initially suggested by Boccotti [1] . The multi-chamber OWCs examined here are fixed on the seabed and have a slit opening at the seaward side. The physical modelling was undertaken in the flume of the COAST laboratory of the University of Plymouth. The devices were tested in uni-directional regular and irregular wave conditions, with and without power take-off (PTO) mechanism, essentially also testing absorbing seawalls. The aim of the study is to present a preliminary comparison related to the geometry of OWCs under some typical wave conditions and suggest potential shape improvements towards an overall optimization of the devices that takes into account both the hydrodynamic efficiency of the OWC and other design aspects, such as the wave run-up. The present study also endeavours to highlight potential benefits from incorporating OWCs in coastal defence as absorbing seawalls. [ABSTRACT FROM AUTHOR]

Various studies investigated the behaviour and the performance of Oscillating Water Columns (OWCs) suggesting many alternative design concepts to improve the efficiency of the device. The OWCs examined here are fixed on the seabed and have a slit opening at the seaward side. The present study investigates the applicability of a multiphase Reynolds Averaged Navier-Stokes (RANS) numerical model for simulating the interaction between an OWC and regular and irregular waves. An initial validation of the open-source computational fluid dynamics (CFD) software package OpenFOAM with the wave generation and absorption toolbox waves2Foam is performed against experimental results obtained at the COAST laboratory of the University of Plymouth. The main aim of the study is to complement to the validation of RANS CFD models and later employ the broadly used numerical tool for further studies for better understanding the behaviour of the OWCs. A method based on mechanical damped oscillations for calculating the eigen frequency of the device from a decay test is presented and compared with the performance curve. The strength of CFD modelling for obtaining better insight to the hydrodynamics of OWCs is also demonstrated. [ABSTRACT FROM AUTHOR]

The present study aims at providing more data and insights for the hinged type WEC, especially focusing on the two-body hinged raft WECs. Two WECs are considered: a well-studied generic hinged raft WEC (G-HRWEC) and a 1:25 scale designed hinged raft WEC (D-HRWEC). The open-source tool WEC-Sim is employed in numerical studies. Referring to the published numerical data for G-HRWEC, corrections are proposed to the WEC-Sim model which are shown to realise the ability of WEC-Sim to model the two-body hinged WEC. For the 1:25 scale D-HRWEC, the physical results show that the relative hinge motion between the rafts is predominately linear under small waves, but significant nonlinearities like viscosity, submergence and overtopping exist under large oscillations. The updated WEC-Sim model is used to simulate this D-HRWEC and is validated with experiment data, showing good representation of the nonlinear behaviour observed in physical experiments with low computation expense. Annual average power of ∼83 kW is predicted for the D-HRWEC in full scale at EMEC site, using the validated WEC-Sim model. The power performance of D-HRWEC is shown to be dependent on the wave steepness. The updated WEC-Sim is provided and can be directly used to model any two-body hinged WECs dominated by linear hydrodynamics. For realistic devices, representative nonlinear terms need to be carefully identified via physical data or computational fluid dynamic simulations and then added into the updated WEC-Sim to improve the modelling accuracy. Following the theory and method given in this work, the updated WEC-Sim for two body hinged raft WEC can be re-developed to extend the WEC-Sim application for WECs or platforms with numbers of hinge connections. • Physical and numerical tests of a designed hinged raft WEC are presented. • Corrections in open-source tool WEC-Sim are proposed to model hinged raft WEC. • Performance of the updated WEC-Sim model is validated by the physical data. • Effects of viscosity, submergence, overtopping, and wave steepness are discussed. • Annual average power of ∼83 kW by this WEC for the EMEC site is predicted. [ABSTRACT FROM AUTHOR]