Hydrodynamic assessment of artificial shell blocks for coastal protection

Abstract

As a novel type of composite breakwater, hollow artificial shells based on rubble mound bases are proposed. The main concept is using shapes from nature to overcome a nature phenomenon (waves). This type of shells is distinguished from other species. Its length and width are almost twice the height, which increases the stability of every individual shell. Additionally, the out-layer grooves and the semicircular shape smoothly dissipate incident waves. The new composite breakwater was investigated physically in a wide wave flume under the effect of regular waves. The breakwater performance was introduced through wave reflection, wave transmission, and wave dissipation coefficients. Several varying wave actions (wave height, wave period) were applied to the breakwater in four states: emergent, partially submerged, submerged and fully submerged. The partially submerged case showed the best efficiency compared with other states. The reflection coefficient ranges from 0.16 to 0.46, the transmission coefficient ranges from 0.3 to 0.48, and the dissipation coefficient ranges from 0.75 to 0.92. The Partially submerged breakwaters have been compared with some of the most commonly used types of breakwaters, and have shown to have better efficiency, particularly in areas with short coastal waves. Also, the crest width of a submerged breakwater can be reduced dramatically to less than half, by deploying artificial shell blocks on the crest.