Hydrodynamic Analysis Of Horizontal And Vertical Plate Type Breakwater

Horizontal and vertical plate can be considered as a new type breakwater.It can be installed before large offshore marine structures to prevent wave from directly acting.It can also be set in zone of wave erosion or marine culture to reduce wave force.In this paper boundary element method is utilized to investigate wave-plate interaction.The transmitted and reflected wave coefficients,added mass,damping,wave exciting force,motion response, flow field analysis are systematically studied and their relations with plate thickness, submergence and length are obtained.It is found that:(1) The mechanism of wave elimination of this type breakwater is due to the return flow caused by water field above plate.The return flow interacts with incident wave and the whole flow field is drastically disturbed and the velocity of water particle is decreased.(2) Both surface horizontal plate and vertical plate are efficient for short wave elimination,but the vertical plate is more effective.The submerged horizontal plate works more effectively than the vertical plate in intermediate wave range.When the plate is infinitely near to the free surface,the frequency range of wave elimination is expanding and zero transmitted wave coefficient will occur.(3) Adding mass turns out to be negative when the horizontal plate and the vertical plate are infinitely near to the free surface.Added mass of surface horizontal or vertical plate is singular when wave number is zero.(4) For same submergence,heave is the control force for the horizontal plate and sway is the control force for vertical plate.Roll force of vertical plate is much larger than the horizontal plate's.