Analisa Tegangan Mooring pada Floating breakwater Tipe Gergaji dengan Pemodelan Fisik

Floating breakwater merupakan solusi alternatif dari penggunaan fixed breakwater karena dapat digunakan secara efektif di daerah pesisir dengan kondisi tertentu, desain yang fleksibel untuk dikembangkan, dan instalasinya lebih mudah. Salah satu aspek dasar dalam desain floating breakwater adalah sistem mooring, karena digunakan untuk menjaga struktur tersebut tetap pada posisinya dan selain itu juga akan mempengaruhi kinerjanya. Penelitian ini bertujuan untuk mengetahui besarnya tegangan mooring maksimum pada tali mooring melalui model fisik. Penelitian dilakukan pada floating breakwater tipe gergaji dan pontoon sebagai pembanding. Model floating breakwater dibuat dari bahan Polylactid Acid dan model tali mooring digunakan jenis polyethylene. Pengujian fisik dilakukan di laboraturium wave flume dengan gelombang irregular dan variasi tinggi gelombang (Hs), periode gelombang (T), elevasi muka air (d), dan sudut mooring (q). Hasil penelitian ini diperoleh nilai tegangan mooring maksimum pada floating breakwater tipe gergaji dan tipe pontoon pada sudut mooring 30⁰ dan elevasi muka air 45 cm secara berturut turut yaitu 5,278 N dan 4,913 N, sedangkan tegangan terkecil terjadi pada sudut mooring 60⁰ dan elevasi muka air 41 cm secara berturut turut yaitu 1,030 N dan 1,273 N. Pada perbandingan nilai tegangan mooring antara floating breakwater tipe gergaji pada sudut mooring (30o, 45o, 60o) adalah lebih besar 10.82%-19.71%, 24.00-40.94%, dan 22.2%-39.42% terhadap tipe pontoon pada elevasi muka air 41cm, 43cm dan 45cm secara berturut-turut

Research on Wave Attenuation Performance of Floating Breakwater

In this study, a new type of double-pontoon floating breakwater was designed to improve the wave attenuation performance through the addition of suspended Savonius propeller-blade. Its hydrodynamic characteristics were studied through numerical simulations and performance-testing experiment. The following investigations were performed in this study: Firstly, wave theory and hydrodynamic theory were combined to calculate the wave attenuation performance and motion response of double-pontoon floating breakwater under linear wave conditions. The numerical results showed that the wave attenuation performance was better under a specific wave period and height, the transmission coefficient reached a relatively small value, and the mooring line tension responded periodically and satisfied the condition of maximum breaking force. Secondly, three key geometric parameters of breakwater were researched, including the relative spacing of pontoons, the relative spacing between pontoons and blades, and the height–diameter ratio of Savonius blades. The calculation results showed that the pontoon spacing was closer to the wavelength and the breakwater wave attenuation performance was better. Lastly, experimental tests were also performed on the new double-pontoon floating breakwater and the results showed that the wave attenuation performance and numerical projections were basically the same, which verified the validity and effectiveness of the design method.

Hydrodynamic Performance of a Multi-Module Three-Cylinder Floating Breakwater System under the Influence of Reefs: A 3D Experimental Study

As the technical and theoretical research of floating breakwaters is becoming increasingly mature, the floating breakwaters are now being utilized, especially in offshore reefs. Therefore, it is of practical significance to study the hydrodynamic performance of a multi-module floating breakwater system under the influence of reefs. In this study, a 3D model experiment was carried out on a system consisting of eight three-cylinder floating breakwater modules under the influence of reefs. A wave attenuation mesh cage was incorporated at the bottom of the model. The floating breakwater system was slack-moored in its equilibrium position, and each module was connected by elastic connectors. The reefs were modeled on a bathymetric map of existing reefs in the East China Sea. In this experiment, the wave transmission coefficients, motion responses, and mooring forces of the floating breakwater system were measured. The results showed that the three-cylinder floating breakwater in the beam waves (β = 90°) has excellent wave attenuating performance under the influence of reefs, especially for short-period waves. However, under the influence of the reef reflection wave and the shallow water effect, the motion responses in the three main stress directions of the floating breakwater were large, and there was some surge and pitch motion. Under the influence of the aggregation and superposition of reflected waves on both sides of the reefs, the peak mooring forces in the middle position of the floating breakwater system were the largest at large wave height. The three-cylinder floating breakwater exhibited satisfactory hydrodynamic performance under the influence of reefs. It has broad application prospects in offshore reefs.