Experimental Study On The Performance Of Submerged Breakwater As Shore Protection Structure

In this study the efficiency of the submerged breakwater as shore protection structure has been investigated experimentally. To investigate the performance of the submerged breakwater, experiments are conducted in a two dimensional wave flume which is 21.3m long, 0.76m wide and 0.74m deep. This whole experimental set-up is carried out at the Hydraulics and River Engineering Laboratory of Bangladesh University of Engineering and Technology. A set of experiments are conducted at a still water depth of 50 cm with a fixed rectangular submerged breakwater of three different heights (30 cm,35 cm and 40 cm) for five different wave periods (1.5 sec,1.6 sec,1.7 sec, 1.8 sec, 2.0 sec) in the wave flume mentioned before. The type of wave breaking and the position of wave breaking are simultaneously recorded with a digital video camera. Effects of breakwater height and length along the wave direction on wave height reduction are analyzed. This analysis is expected to serve to assessment the wave height reduction due to submerged breakwater as a shore protection structure. It is clearly seen from this experiment that a submerged breakwater is very effective in reducing the transmitted waves. For same wave period higher breakwater can reduce the incident wave height more than the smaller breakwater. From the experimental investigations it is found that relative breakwater width, B/L ( B is the breakwater width and L is the wave length) and relative breakwater height, h s /d (h s is the breakwater height and d is the still water depth) are the important parameters for reducing the wave height. As the relative structure height h s /d increases, reduction of incident wave increases due to breaking caused by the breakwater. As the relative breakwater width B/L increases, the reduction of wave height also increases.