This paper presents the numerical investigations of an oscillating wave surge converter (OWSC) operating in extreme sea states leading to slamming. We use the open-source computational fluid dynamics (CFD) library OpenFOAM to carry out the two-dimensional numerical simulations. A preliminary study is done to verify the convergence of our results, while scalability tests confirm the high-performance computing capabilities of OpenFOAM and the possibility of extending this study to large three-dimensional configurations. The OWSC device is simulated with both incompressible and compressible solvers, and the results are compared against previous numerical and experimental results. It is shown that an incompressible solver can capture the dynamics and general behavior of the flap device. Nevertheless, the compressibility effects can be reproduced only with the aid of a compressible solver, which takes into account the density changes in the air and water phases. Those effects produce high-frequency, small oscillations on the seaward side of the flap but do not contribute to further increasing the peak pressure values characteristic of slamming.
The use of renewable energies, such as wind and solar, has experienced a noticeable increase in recent years. However, other sources of renewable energies, such as the one extracted from ocean waves nearshore, still remain largely underexploited at present. Therefore, more experiments and accurate numerical simulations need to be carried out in this area with special focus on structure survival as a consequence of harsh ocean conditions.
This paper focuses on the Oyster oscillating wave surge converter (OWSC) (Whittaker and Folley, 2012), which consists of a flap device hinged on the seabed and driven back and forth by the action of waves. The energy taken from the waves is utilized to pump fresh water into a hydraulic plant inshore, where it is finally converted into electricity. OWSCs obtain their maximum efficiency in nearshore locations of shallow water depths, where they acquire larger motions from the waves. One of the current challenges of the OWSCs is their survivability in extreme sea states, e.g., winter sea storms (Kay, 2014), in which large and infrequent extreme waves may compromise their structural integrity and consequently lead to an increase in their maintenance costs. Furthermore, global warming and climate change are likely to increase the frequency as well as the intensity of storms and hurricanes, which may influence the design of future OWSCs.
