ICMT2014, 7 th -9 th July 2014, Glasgow, UK Numerical Simulation of a Ducted Oscillating Water Column Islam Amin 1* , Saishuai Dai 2 , Qing Xiao 2 1. Department of Naval Architecture and Marine Engineering, Port Said University, Egypt 2. Department of Naval Architecture, Ocean and Marine Engineering, Strathclyde University, UK Abstract: Oscillating Water Column (OWC) wave energy converter system is one of the most successful wave energy extraction technologies. Adaption of a ducted entrance to the OWC chamber is proposed in this study, aiming to improve its hydrodynamic energy extraction performance. A two-dimensional CFD simulation for a traditional onshore OWC device is carried out and the results are validated with available experimental, numerical and analytic results. The flow is considered as incompressible, and the power take-off is simulated using an orifice. The URANS equations are employed to solve the presented numerical model. The effect of duct on converting wave energy to pneumatic power is investigated. Significant increase in the OWC device after adding the proposed duct entrance was observed, in the small wave’s frequency. Keywords: Oscillating Water Column (OWC), duct, Renewable Energy Devices, CFD. Article ID: RE-SU-D 1. Introduction The Oscillating Water Column (OWC) Wave Power Converter is a renewable energy device which is used for extracting power from wave energy. Many countries including the United Kingdom, Japan, China, Norway, and Spain have been at the forefront of the development in this area of technology. However, the challenges with the research are to design a system capable to withstand the extreme weather conditions and increase the efficiency of these systems. There have been many developments in Oscillating Water Column (OWC) technology over the last 50 years. These technologies can be categorized into shoreline; breakwater, near-shoreline, and floating OWC wave energy capture systems. Some examples of shoreline prototypes, as mentioned in the (Falcao, 2010) survey, include Sakata in Japan in 1990, Pico in Portugal in 1999, Islay and LIMPET by Wavegen Ltd. at Isle of Islay in the United Kingdom in 1988, and 2000 respectively. One of the largest fixed OWC structures in size and electricity generation capability was OSPREY, developed by Wavegen in Scotland in 1996. OSPREY was planned to be a completely fixed base, near-shoreline, deep water structure with the capacity to generate up to 2MW of electricity. Unfortunately, it was destroyed by the waves during its installation at Dounreay, Scotland (Falcao, 2010). There have been several experimental, numerical and analytical research work conducted with the hydrodynamic aspects of OWC. Potential theory was used in analytical work by Evan (Evan, D. and Porter, R., 1995)to consider a rectangular OWC in terms of the width of the internal chamber and submergence depth of the front wall, neglecting the viscous effect. Boccotti (Boccotti, 2007)found that an OWC with additional vertical duct (U-OWC) has better performance than that of a conventional OWC. U-shape duct is proposed in this study to develop the OWC performance. Two-dimensional numerical study of geometric optimization of an OWC using commercial code Fluent is presented by Gomes, (Gomes, M., Nascimento, C., Bonafini, B., Santos, E., Isoldi, L. and Rocha, L., 2012). All geometrical parameters were kept constant except the width to height ratio of the chamber. He concluded that the optimum width to height ratio of OWC chamber is 0.84 and the worst is 0.14. The effect of geometry and dimensions of the chamber on the efficiency of OWC is studied by (Bouali, B.and Larbi, S., 2013). They concluded from simulation results that the size of the chamber, the immersion depth of the front wall of the device, and its orientation versus the flow direction all have a significant impact on the performance of the device. Various geometrical designs of an OWC system are experimentally investigated by (Dizadji, N. and Sajadian, S., 2011), in order to maximize energy harness. They observed that, decreasing the front wall angle considerably increased the outflow of air from the chamber. They also found that the parallel arrangement of the front wall plate and the back-end plate of the chamber has the maximum efficiency compared to other arrangements. Experimental investigation on the influence of front wall geometry on the OWC’s performance was conducted by (Morris, M., Irvin, R. and Thiagarajan, K., 2007) also. Front wall draught, thickness and aperture shape of the submerged front wall were studied. The experiment has shown that, increasing front wall submergence or wall thickness leads to reduction in the hydrodynamic efficiency of OWC in short waves. A numerical method based on a two-phase level set with the global mass correction and immersed boundary