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Abstract This study presents a three-dimensional numerical simulation of a circular bottom-sitting OWC device for wave energy extraction. The numerical model is based on Reynolds-Averaged Navier-Stokes equations with a modified k- ω turbulence model and a Volume-of-Fluid method to track the air-water surface. The numerical model and setup are validated against a set of wave-flume experimental results. The numerical simulation provides detailed flow-field information, which allows for an analysis of the spatial non-uniformity inside the OWC chamber and the measurement error associated with it. New numerical results show that vortex shedding at the sharp edge of the OWC chamber enhances the spatial non-uniformity inside the OWC chamber through a resonant sloshing mechanism. The enhanced spatial non-uniformity can affect the accuracy of the experimentally-determined quantities such as the extraction efficiency of the OWC chamber and the characteristics of the power take-off device; Suggestions are also provided to improve the accuracy of the experimentally-determined quantities that may be affected by the spatial non-uniformity inside the OWC chamber. [ABSTRACT FROM AUTHOR]

Abstract: Brossard et al. ([2009. Coastal Engineering 56, 11–22], hereinafter referred to as BPBD) presented an experimental study of the higher harmonics induced by a submerged horizontal plate and a submerged rectangular step. In this paper we present a numerical study of the wave scattering by a submerged thin plate as described in BPBD. A fully nonlinear numerical wave tank based on a desingularized boundary integral equation method (DBIEM) was developed for the interactions between non-breaking waves and a fixed 2D body. We also present a new set of experimental data on regular waves interacting with a submerged thin plate with different submergences, with the aim of removing the influences of multiple reflections between the wave-maker and submerged structures in a wave flume. We compare our numerical simulations with our experiments as well as the experiments of BPBD. The comparison shows that DBIEM can predict satisfactorily the multiple wave reflections caused by the thin plate as well as the main features of the generation and transmission of higher harmonic waves. [Copyright &y& Elsevier]

Flow characteristics in the vicinity of a bottom-sitting wave energy converter are important for understanding the wave loading on and the local scour around the structure. Based on three-dimensional numerical simulation results, key features of the vortex flow in the vicinity of a circular oscillating water column (OWC) supported by a C-shaped structure are discussed, including vortices shed from the lower tip of the OWC chamber and the two edges of the C-shaped support structure. Numerical results reveal a time-mean flow pattern in the vicinity of the C-shaped structure. There is a strong connection between the near-field flow pattern and the local morphological change at the C-shaped support structure. [ABSTRACT FROM AUTHOR]

Abstract: Water waves induce a slow drift of an object floating on the water surface. In this study, we examined, by a series of laboratory experiments, the drift motion of small rigid floating objects driven by regular waves in deep water. Different shapes of planar objects, including square, circular and elliptical, were investigated for two different submergences, and their drift motions in waves were determined using an infrared motion monitoring system. The corresponding measurements enabled the quantification of the drift characteristics with respect to the wave characteristics and object shapes. Numerical simulations based on an existing theory were presented and comparisons between the experimental data and the predictions by the existing theory were performed. [Copyright &y& Elsevier]