Stepped sea bottom effects on the efficiency of nearshore oscillating water column device

The present study analyses the role of stepped bottom topography in increasing the efficiency of a nearshore oscillating water column (OWC) device. The mathematical problem is formulated in the two dimensional Cartesian coordinate system under the linear water wave theory. Two different mathematical approaches are adopted to solve the associated boundary value problem (BVP), one is the method of matched eigenfunction expansion and the other is the boundary integral equation method (BIEM). The numerical results show good agreement with the analytical results. Three different horizontal positions of the step are considered. The effect of the distance of the step from the water column barrier and the height of the step on the efficiency of the OWC device are discussed in detail. The results show that inclusion of an artificial step at the sea bottom with proper tuning may lead to a significantly increased capacity of power absorption of the device.