الفهرس 
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Abstract
The importance of coastal protection increases with the increase of coastal development. Soft and hard protection measures are the most used techniques. However, hard structures are still preferable. Hard structures are characterized by a long lifetime and high stability in high storms states. Many innovative, environmentally friendly hard coastal protections measured have been proposed and used for specific applications.
Breakwaters, for example, are structures designed to sustain and dissipate the energy produced by waves. They help stabilize the coast and preserving ports, beaches, and other coastal resources and habitats. Due to their aesthetic advantages and high structural efficiency, semi-circular breakwaters have been used in various locations worldwide. Coastal structures are subjected to hydrodynamic forces usually estimated through physical models and experiments, which is still a realizing tool to study and design such systems. However, these models are difficult to implement, requiring high costs and long experimental procedures. Thus, alternative methodologies for analyzing the hydrodynamic efficiency of these structures are extremely beneficial.
The main objective of this research is to develop and check a new coastal structure shape. Corrugated Semi-circular Breakwater (CBW) is proposed. This structure is modified from the Semi-circular Breakwater (SCBW), one of the hard protections used in Japan and China, to increase its efficiency in coastal protection and electricity generation. A comparative study between CBW and SCBW is carried out physically in a two dimensions wide wave flume with dimensions 1.2*1.2*40 m in the Lab. of Coastal Research Institute (CoRI). A computational fluid dynamics tool (Flow-3D) is used to compare the physical models numerically. The numerical model was calibrated and tested using experimental data, considering the effects of water depth and wave characteristics.
The study checked the effect of the structure in emerged, low crest, and submerged conditions under different conditions. The reflection, transmission, and dissipation coefficients are used as the efficiency indicators, in addition to changes in current velocity.
The results showed that the numerical model accurately simulates wave flume and semi-circular breakwater’s interaction with the fluid. Furthermore, CBW has demonstrated its high efficiency in wave dissipation, current velocity reductions, and bed stability than SCBW. CBW shows significant reduction in wave transmission in partially submerged scenario compared to SCBW. It is recommended to use the CBW as a protected structure within the recreational coastal areas.