Wave Control Performance of Tide-Adapting Low-Crested Structure

Abstract

Low-Crested Structures (LCSs) are aesthetically apt coastal structures with wave and sand drift control functions. However, they are inappropriate in waters where the tidal range is large because the crest width and height must be above certain levels to allow the breakwater to carry out these functions. Forced wave breaking cannot be induced during high tide because the crest depth increases. Therefore, a Tide-Adapting Low-Crested Structure (TA-LCS) is proposed to overcome the problems caused by large tidal ranges. The hydraulic performance of the proposed LCS was evaluated and compared with that of a typical LCS via hydraulic model experiments. The typical LCS showed an excellent wave screening effect with an average transmission coefficient of 0.4 under the conditions of F-b/H-i=0.29-0.67 and B/L-i=0.09-0.15. The wave screening performance of the new type of LCS was 9.5-28.8 % lower than that of the typical LCS. However, the wave screening performance of the new type of LCS decreased only by 9.1-10.4 % under the condition of F-b/H-i <= 1 and only by 24.3 % under the condition of F-b/H-i=4. Therefore, the new type of LCS proposed in this study is expected to exhibit its wave control functions during high tide even when installed in a coastal area with a large tidal range.