Experimental and Numerical Investigation on Wave Interaction with Submerged Breakwater

Abstract

Experimental studies are carried out in a two-dimensional wave flume (21.3 m long, 0.76 m wide and 0.74 m deep) to investigate the performance of rectangular type submerged breakwater. A set of experiments are carried out at 50 cm still water depth with fixed submerged breakwaters 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 and 2.0 sec) in the same wave flume. For fifteen run conditions, water surface elevations are collected at six different locations both in front of and behind the breakwater. Also the type of wave breaking and 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. It is found that both the relative structure height (hs/h) and relative breakwater width (B/L) have strong influence in reducing transmitted wave height. Experimental analysis prevails that the reduction of transmitted wave height are 50%, 58% and 68% for relative structure height (hs/h) of 0.6, 0.7 and 0.8 respectively, for a particular value of relative breakwater width (B/L =0.35). Also, the reduction of transmitted wave height is 32% and 50% for relative breakwater width (B/L) of 0.25 and 0.4 respectively, for a particular value of relative structure height (hs/h =0.6). A two-dimensional numerical model based on the SOLA-VOF method has been developed in this study to investigate the wave interaction with fixed submerged breakwater. The developed model can simulate time series water surface profiles, water particle velocity field, VOF function F, pressure around a breakwater. The water surface profiles and wave breaking positions in various wave conditions simulated by the developed numerical model show good agreement with the experimentally measured values. The numerical model developed in this study is expected to serve as tool to analyze wave deformation due to submerged breakwater and will be important for designing submerged breakwater as a coastal protection measure.