Wave Attenuation Properties of Composite Undulating Submerged Breakwaters

This study investigates the attenuation of composite impermeable sinusoidal breakwater by physical experiment with combination of breakwaters collocated with various widths and heights. The breakwaters are located in different permutations and combinations from one set to three sets on the bottom as various undulating slope, and explore the attenuation effect when waves propagated through the periodic-gradational undulating terrain, the optimizations of a variety of sinusoidal breakwater are preliminary analyzed. This article discusses the properties of wave reflectance K_r, transmittance K_t, energy loss coefficient K_L, and the attenuation of such composite terrain, including optimal combinations of such obstacles. Desperate diversities are found in the K_r, K_t, and K_L, due to varied combination of the breakwater under the circumstances of various wave conditions. The results show that the attenuation of long waves is effective, and is affected by the nonlinearity and dispersion. The transmittance K_t shows that composite of rapidly varied combinations is better than a gradually varying section. Increasing the quantity of composite breakwater also improved the attenuation effect on both the rapidly varied cases and segmented gradually varying cases. The optimal combination to eliminate the energy of long waves is also discussed.