01 Jan 2007
TL;DR: In this article, the authors numerically analyzed the flushing effects and the likelihood of a vertical breakwater consisting of immersed water channel and water chamber, originally proposed by Nakamura (1999, 2003, 2005) for the alleviation of reflected waves, as a wave energy extraction measure.
Abstract: We numerically analyze the flushing effects and the likelihood of a vertical breakwater consisting of immersed water channel and water chamber, originally proposed by Nakamura (1999, 2003, 2005) for the alleviation of reflected waves, as a wave energy extraction measure. As a wave driver, we use the Nervier-Stokes equations and mass balance equation, and the numerical integration of which is carried out based on the smooth particle hydrodynamics with a Gaussian Kernel function. As a water level in front of curtain wall, where an anti-node of standing wave due to partial reflection is located, approaches its lowest level, a unidirectional flow in the water chamber formed by a preceding wave starts to move offshore. Once it exits a water chamber, this energetic flow feeds necessary energy for the vortex in front of the water chamber to sustain enough time until next wave comes. Considering the facts that an intensity of the flow absorbed through the immersed water channel is strongly proportional with an extent and strength of the vortex formed on offshore side of front curtain wall and a curved path line of sucked water particles, we can deduce that aforementioned vortex is responsible for the flushing effects of the vertical breakwater consist of immersed water channel and water chamber. It is also shown that net flux through the immersed water channel increases as the mass inflow into a water chamber is getting larger (T=1.4sec, Le=6 cm), which also confirm our conclusion.
TL;DR: In this article, a wave-induced swirl water chamber (SWC) for breakwater and wave power generation is introduced and its applicability to wave power generating in the coastal waters of Korea is investigated.
Abstract: In this paper, a wave-induced swirl water chamber (SWC) for breakwater and wave power generation is introduced and its applicability to wave power generation in the coastal waters of Korea is investigated. The SWC type of wave power generation is a way to drive a turbine using the unidirectional swirl flow that is induced in the back of a curtain wall of a breakwater due to incident waves. The typical wave characteristics are obtained by analyzing the annual statistical wave data from KHOA (Korea Hydrographic and Oceanographic Administration). A numerical analysis is carried out on the variations in the SWC entrance height, wave height, and different installation conditions. For the numerical analysis, a commercial code, Fluent based on FVM, is used. As the entrance height decreases, the mass flow rate through the entrance is rarely changed, whereas the magnitude of the flow velocity of the smaller entrance height is greater than the other ones, which is better for the formation of an SWC swirl flow inside and the flow kinetic energy at the entrance. In cases of installation conditions where a wall is place behind and under SWC, it has been shown that the mass flow rate through the entrance is greater than that in the open condition, and sufficient flow kinetic energy is generated in the entrance for wave power generation. However, the swirl flow kinetic energy is relatively small. Thus, in the future, it is necessary to study the swirl flow generation, which is affected by the SWC shape.