Abstract
To evaluate the trapped wave energy and energy loss, the problem of wave scattering by twin fixed vertical surfacepiercing plates over a stepped bottom is numerically simulated using the open source package OpenFOAM and the associated toolbox waves2Foam. The volume of fluid (VOF) method was employed to capture the free surface in the time domain. The validation of the present numerical model was performed by comparing with both the analytical and experimental results. The effects of the spacing between two plates and the configuration of stepped bottom on the hydrodynamic characteristics, such as reflection and transmission coefficients, viscous dissipation ratio, and relative wave height between the plates (termed as trapped wave energy), were examined. Moreover, the nonlinear effects of the incident wave height on the hydrodynamic characteristics were addressed as well. The results show that the step configuration can be tuned for efficient-performance of wave damping, and the optimum configurations of the step length B, the step height h1 and the spacing b, separately equaling λ/4, 3h/4, and 0.05h (λ and h are the wavelength and the water depth, respectively), are recommended for the trapping of wave energy.
Highlights
The oil crisis of the 1970s opens up a new era of renewable energy exploitation (Vicinanza et al, 2014) and the most concerned areas include solar, wind and ocean energies (López et al, 2013)
To investigate the complex hydrodynamic behaviors and further enhance the amount of wave energy coming into the column, basically, the oscillating water column (OWC) device can be regarded as two truncated surface-piercing plates with an open top, which is served as a breakwater system
Rezanejad et al (2013) examined the role of stepped bottom topography in increasing the efficiency of an onshore OWC device, and the results showed that a proper configuration of sea bottom step significantly improved the capacity of power absorption
Summary
The oil crisis of the 1970s opens up a new era of renewable energy exploitation (Vicinanza et al, 2014) and the most concerned areas include solar, wind and ocean energies (López et al, 2013). As an important renewable resource, wave energy has the basic characteristics of wide distribution, large energy density, simple collection structure and so on (Ning et al, 2014). The oscillating water column (OWC) wave energy converter (WEC) is widely used for wave energy extraction because of its simple structure, easy maintenance and installation. Due to the wave reflection from the front-wall and the vortex shedding in the vicinity of the lower tip of the frontwall, most incident wave energy is reflected and dissipated, which is one of the key reasons for the low conversion efficiency of the WECs. To investigate the complex hydrodynamic behaviors and further enhance the amount of wave energy coming into the column, basically, the OWC device can be regarded as two truncated surface-piercing plates with an open top, which is served as a breakwater system. In the full-scale sea test, the bathymetry is arbitrary, which has a significant impact on the fluid dynamics
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