Transmission Performance of Submerged Semicircular Breakwaters for Different Radii and Submergence Ratios

Abstract

The paper presents the results of a series of laboratory experiments that were conducted in a 2D monochromatic wave flume of the department to evaluate the transmission characteristics of scaled down semicircular breakwater (SBW) physical models of different radii (R) for different submergence ratios (d/hc), where d is the depth of water and hc is the height of the breakwater crest from the sea bed. The radii of the breakwater models studied were 20 cm, 22.5 cm, 25 cm, and 27.5 cm and d/hc values used varied from 1.067 to 1.667. The wave climate along the Mangalore coast of India was used for arriving at the various wave parameters. Incident wave heights (Hi) used varied from 3 to 18 cm, wave periods (T) ranged from 1.2 s to 2.2 s with water depths (d) of 40 cm, 45 cm and 50 cm. The data collected was analyzed by plotting the non-dimensional graphs depicting the variation of transmission coefficient Kt (Kt = Ht/Hi, where Ht = transmitted wave height) with wave steepness Hi/gT2 for different R/Hi and d/hc values. It was found that transmission coefficient decreased as the incident wave steepness increased for different submergence ratios. Also as d/hc increased, it was found that Kt increased initially and then decreased.