| The breakwater is an important offshore engineering structure which can be used to attenuate waves and protect the safety of ships and other marine structures in protected areas.The traditional breakwater is bottom-fixed,and it has superior wave attenuating performances.However,its construction cost increases sharply with the increase of water depth.In addition,it has strict requirements on the foundation and easily leads to the silting of mud.Compared with bottom-fixed breakwater,the floating breakwater extends the application range of the breakwater.It has many advantages,including low cost,simple construction,convenient layout and permitting water exchange.Owing to these advantages,more and more scholars and researchers pay attention to the floating breakwater.Thus,the development and study of the new floating breakwater is vital.In this dissertation,cost-effective floating breakwaters which have low costs,convenient assembly and disassembly steps and reusability are designed to protect offshore operations.Numerical investigations on their hydrodynamic performance and wave attenuating performances are carried out.The main contents have shown as follows:1.Based on the configurations of the existing floating breakwaters and aiming at the technical wave attenuating requirements of offshore operations,three cost-effective floating breakwaters with different configurations are designed.They are rectangular type,circular-rectangular type and oval type cost-effective floating breakwaters,respectively.According to the sea conditions,wave attenuating requirements,construction cost and installation efficiency,the main parameters of the cost-effective floating breakwaters are determined.2.Based on the viscous fluid theory,STAR-CCM+ is employed to develop a two-dimensional numerical wave flume.The numerical results are compared with the theoretical results to validate the present numerical wave flume.Based on the above studies,a two-dimensional numerical model of a rectangular floating breakwater is built.The wave transmission coefficients,heave,roll,sway motions of the rectangular floating breakwater are calculated and compared with the experimental results to validate the present numerical model.3.The hydrodynamic and wave attenuating performances of the three cost-effective floating breakwaters with different configurations are studied based on the validation of the numerical wave flume and numerical method of the floating breakwater.The influence of wave height and wavelength on the motion responses and wave transmission coefficients of these three cost-effective floating breakwaters with different configurations are analyzed.In addition,the free surface elevation around the rectangular type cost-effective floating breakwaters is observed and the wave attenuating mechanism is analyzed.4.Based on the existing on-site installation technologies of the floating breakwater and taking the features of cost-effective floating breakwaters into consideration,a fast,safe and efficient on-site installation technology for cost-effective floating breakwaters is proposed.This on-site installation technology deals with a series of technical problems,such as lifting,positioning,anchoring,the installation sequence of single body,the installation sequence of mooring line and so on.The results show that the present numerical method has enough accuracy to simulate the hydrodynamic and wave-attenuating performances of the floating breakwater.It is also found that the rectangular type floating breakwater has superior wave attenuating performance than the circular-rectangular type and oval type floating breakwaters.In addition,the wave attenuating performance of the rectangular type cost-effective floating breakwater meet the wave attenuating requirement of the cost-effective floating breakwater.Thus,the rectangular type is defined as the final configuration of the cost-effective floating breakwater. |
