A Theoretical Study of the Hydrodynamic Performance of an Asymmetric Fixed-Detached OWC Device

The chamber configuration of an asymmetric, fixed-detached Oscillating Water Column (OWC) device was investigated theoretically to analyze its effects on hydrodynamic performance. Two-dimensional linear wave theory was used, and the solutions for the associated radiation and scattering boundary value problems (BVPs) were derived through the matched eigenfunction expansion method (EEM) and the boundary element method (BEM). The results for the hydrodynamic efficiency and other important hydrodynamic properties were computed and analyzed for various cases. Parameters, such as the length of the chamber and the thickness and submergence of the rear and front walls, were varied. The effects on device performance of adding a step under the OWC chamber and reflecting wall in the downstream region were also investigated. A good agreement between the analytical and numerical results was found. Thinner walls and low submergence of the chamber were seen to increase the efficiency bandwidth. The inclusion of a step slightly reduced the frequency at which resonance occurs, and when a downstream reflecting wall is included, the hydrodynamic efficiency is noticeably reduced at low frequencies due to the near trapped waves in the gap between the OWC device and the rigid vertical wall.The current investigation was developed under the framework of the Basque Government (IT1314-19 research group). The authors additionally thank the funding provided by CEMIE-Océano (Mexican Centre for Innovation in Ocean Energy). Project FSE-2014-06-249795 financed by CONACYT-SENER Sustentabilidad Energética

The Influence of the Chamber Configuration on the Hydrodynamic Efficiency of Oscillating Water Column Devices

Based on the two-dimensional linear wave theory, the effects of the front wall thickness and the bottom profile of an Oscillating Water Column (OWC) device on its efficiency were analyzed. Using the potential flow approach, the solution of the associated boundary value problem was obtained via the boundary element method (BEM). Numerical results for several physical parameters and configurations were obtained. The effects of the front wall thickness on the efficiency are discussed in detail, then, various configurations of the chamber bottom are presented. A wider efficiency band was obtained with a thinner front wall. In a real scenario having a thinner front wall means that such a structure could have less capacity to withstand the impact of storm waves. Applying the model for the case of the Mutriku Wave Energy Plant (MWEP), findings showed that the proposed bottom profiles alter the efficiency curve slightly; higher periods of the incoming water waves were found. This could increase the efficiency of the device in the long-wave regime. Finally, the numerical results were compared with those available in the literature, and were found to be in good agreement.The present research has been developed under the framework of CEMIE-Océano (Mexican Centre for Innovation in Ocean Energy). Project FSE-2014-06-249795 financed by CONACYT-SENER- Sustentabilidad Energética. In addition, the authors would like also to express their gratitude for the funding provided by the UPV/EHU [PPGA20/26 research group] and the Basque Government (IT1314-19 research group)

The hydrodynamic performance of a shore-based oscillating water column device under random wave conditions

ABSTRACT: The testing of scale models is crucial if we are to continue the development of wave energy converters. Investigations have examined the interaction of shore-based Oscillating Water Column (OWC) devices with regular water waves that impact the device perpendicularly in flumes or wave basins. However, these simplistic experiments might misrepresent the effectiveness of an OWC system. This study examines the interaction of irregular, oblique, water waves with a shore-based OWC device in terms of its hydrodynamic performance. In a spectral wave basin, a series of experiments were performed on a scale model of a single chamber of the Mutriku Wave Energy Plant. Wave propagation conditions were examined to see their impact on the hydrodynamic performance of a fixed OWC system. The wave amplification factor, hydrodynamic efficiency, non-dimensional air pressure inside the chamber, and non-dimensional water pressures on the chamber walls were evaluated. The results show that when the free surface is close to the front wall lip, the hydrodynamic efficiency increases, while the effect of significant wave height was seen to be more important in the wave amplification. Finally, it was found that the hydrodynamic efficiency under random waves is lower than that in experiments under regular waves reported previously.The current study was conducted within the scope of CEMIE-Océano (Mexican Centre for Innovation in Ocean 392 Energy). Project FSE-2014-06-249795 financed by CONACYT-SENER- Sustentabilidad Energética. Furthermore, 393 the authors would like to express their gratitude to the Basque Government through the research group (IT1514/22) 394 and are grateful for the support of Felipe Ernesto Puc Cutz and Enrique Alejandro Mangas Che in the laboratory

Experimental Investigation of the Hydrodynamic Performance of Land-Fixed Nearshore and Onshore Oscillating Water Column Systems with a Thick Front Wall

Most experimental research on land-fixed Oscillating Water Column (OWC) systems assume that the OWC-water wave interaction happens with waves that propagate normally towards the device. However, the angle of incidence of the waves can determine the performance of the OWC, in particular the wave period at which the device resonates. In this study, an experimental investigation to examine the interaction of regular, oblique, water waves with a land-fixed, thick-front wall OWC device in terms of its hydrodynamic performance is reported. A 1:20 Froude scale was used to replicate a single chamber of the Mutriku Wave Energy Plant (MWEP), and a series of tests were carried out in a spectral wave basin. The goal of this study is to look at how incident wave direction and device location affect the hydrodynamic performance of land-fixed OWC systems in regular wave conditions with varying wave heights. The hydraulic performance includes the assessment of the wave amplification factor, hydrodynamic efficiency, the non-dimensional air pressure inside the chamber and non-dimensional water pressures on the chamber walls. The findings show that, for the nearshore OWC device, the period at which resonance occurs decreases when the incident wave angle increases. For the corresponding wave angles, similar results were found for the onshore and nearshore OWC devices, with a slight frequency shift in the bandwidth of the hydrodynamic efficiency. Furthermore, it was found that when wave height increases, the hydrodynamic efficiency improves for both short and long wave periods, with the exception of the resonance period, where the trend is reversed. Finally, regardless of the location, an OWC device with a thick front wall performs well when interacting with intermediate and long-period waves

Experimental Investigation of the Hydrodynamic Performance of Land-Fixed Nearshore and Onshore Oscillating Water Column Systems with a Thick Front Wall

Most experimental research on land-fixed Oscillating Water Column (OWC) systems assume that the OWC-water wave interaction happens with waves that propagate normally towards the device. However, the angle of incidence of the waves can determine the performance of the OWC, in particular the wave period at which the device resonates. In this study, an experimental investigation to examine the interaction of regular, oblique, water waves with a land-fixed, thick-front wall OWC device in terms of its hydrodynamic performance is reported. A 1:20 Froude scale was used to replicate a single chamber of the Mutriku Wave Energy Plant (MWEP), and a series of tests were carried out in a spectral wave basin. The goal of this study is to look at how incident wave direction and device location affect the hydrodynamic performance of land-fixed OWC systems in regular wave conditions with varying wave heights. The hydraulic performance includes the assessment of the wave amplification factor, hydrodynamic efficiency, the non-dimensional air pressure inside the chamber and non-dimensional water pressures on the chamber walls. The findings show that, for the nearshore OWC device, the period at which resonance occurs decreases when the incident wave angle increases. For the corresponding wave angles, similar results were found for the onshore and nearshore OWC devices, with a slight frequency shift in the bandwidth of the hydrodynamic efficiency. Furthermore, it was found that when wave height increases, the hydrodynamic efficiency improves for both short and long wave periods, with the exception of the resonance period, where the trend is reversed. Finally, regardless of the location, an OWC device with a thick front wall performs well when interacting with intermediate and long-period waves