Hydrodynamic performance of an offshore Oscillating Water Column device mounted over an immersed horizontal plate: A numerical study

Abstract

The hydrodynamic characteristics of an OWC device coupled with an immersed horizontal plate was explored numerically by utilizing the CFD toolbox OpenFOAM. The influences from the variation of immersed depth (i) and the plate length (l) on related parameters of plate-integrated system, including energy absorption efficiency (ξ), reflection and transmission coefficient (Cr and Ct) and energy dissipation coefficient (Kd), were examined for an optimal structure configuration. In addition, the novel WEC-plate integrated system was compared with an OWC device mounted over a submerged breakwater at the same immersed depth in terms of hydrodynamic parameters and vorticity field. The results show that the integration with an immersed horizontal plate can greatly improve the performance of OWC device and generally a smaller immersed depth is much likely to obtain a reasonable transmission coefficient and more beneficial for the energy extraction. There exists a relatively optimal length of plate, which is conducive to the wave energy utilization especially subjected to short waves, but a larger length behaves better in the aspect of coastal protection. Moreover, the comparison implemented between OWC-breakwater and -plate demonstrates that although the integration of OWC and breakwater is more competitive in coastal protection, the plate-integrated system is more recommended as an effective tool and medium for extracting and absorbing wave power.