Experimental Study On Hydrodynamic Characteristics Of A Multi-Purpose Oscillating Water Column Device With A Horizontal Bottom Plate

The ocean not only gives birth to life on the earth,but also provides inexhaustible energy resource,known as the "granary of the future." With the concern of depletion of fossil energy and global warming,how to effectively exploit marine energy has become the main theme of current research on sustainable alternatives.For the extraction of wave energy,the OWC(Oscillating-Water-Column)wave energy conversion device is favorite to researchers all over the world due to its simple and reliable operation principle,but the high construction and maintenance cost and low economic benefits block the development of commercialization.Therefore,how to improve its power generation efficiency while reducing related costs in the mean time,and put it into large-scale production as soon as possible has become a hot subject for many scholars to study.In this paper,an oscillating water column wave energy conversion device with a horizontal bottom plate is proposed,which can also serve as a breakwater structure.Firstly,under different wave conditions,the hydrodynamic performance of oscillating water column breakwaters with five different horizontal bottom-plates was experimentally studied.And both the wave-damping ability and the energy dissipation of the novel breakwater structures was examined.Consequently,based on the well-studied OWC breakwater structure,a multi-purpose OWC device was proposed by deploying a roof-plate with a circular orifice.The absorption efficiency of the OWC multi-purpose device under different incident wave climates was investigated through changing both the aperture ratio and the horizontal plate width.The hydrodynamic characteristics of the OWC device was explored as well.The experimental results show that for the OWC breakwater,the horizontal bottom-plate width has a significant influence on the hydrodynamic performance of the breakwater.When the horizontal bottom-plate width D=2.0B(B is the horizontal distance between two vertical sheets),the reflection and transmission coefficients of the breakwater are relatively small,while the dissipation coefficient is large.Reducing the reflection coefficient,but effectively blocking the wave and dissipating more wave energy,which have good effects on protecting buildings and coastal structures in the port.For the multi-purpose OWC device,the wave protection and dissipation of the model is better than the breakwater structure due to the existence of the horizontal top-plate and the opening ratio setting.And the energy conversion efficiency of the OWC device is significantly improved over a wider highly-effective wave frequency band by mounting a relatively wider bottom-plate.In addition,based on both the wave-damping ability and the absorption efficiency,the horizontal bottom plate width of D=2.0B and the opening ratio of ?=0.68%are recommended to be the optimal structural parameter of the proposed OWC device in this paper.Of course,a longer horizontal bottom-plate width conducive to further dissipate energy and block waves,but from the perspective of practical construction application,D=2,0B is the maximum width selected in this paper.