Subsea pipeline must be design as stable as possible to prevent failure, considering the external forces from current, wave and soil conditions. Based on these problems, the on-bottom stability ...analysis needs to be considered in the design of the subsea pipeline by referring to the requirements set out in the DNVGL RP F109 2017. The results of the analysis are the value of hydrodynamic force in the horizontal direction which are 99,916 N/m and 204,358 N/m for installation and operating conditions respectively, while the hydrodynamic force in the vertical direction for installation conditions is 46,852 N/m and operating conditions is 192,232. N/m. The result of absolute lateral static stability analysis, the pipe with a concrete coating thickness of 40 mm both in installation and operating conditions is stable, because it has met the criteria. The result of generalized lateral stability analysis, in installation conditions, the displacement of 0,5 and 10 times of pipe diameter have reached the safety factor. Meanwhile, in operating conditions, the displacement of 0,5 times of pipe diameter has not reached the safety factor, while for displacement of 10 times the pipe diameter is alright. Therefore, the concrete ballast thickness needs to be added to become 44 mm. Modeling using ANSYS CFX software was carried out to obtain the value of hydrodynamic forces acting on the pipe. The result of pipe modeling in installation conditions are 83,578 N/m and 57,13 N/m for hydrodynamic forces in the horizontal and vertical directions. The model is verified and categorized as a good numerology and modeling due to the simple data and information as an input in ANSYS CFX.
Exploration of ocean current energy allows for the development of turbines as the primary conversion device. Turbine technologies have been developed in various types, including bio-inspired ...turbines, such as the humpback whale fluke turbine. In this study, the achievement of a humpback whale fluke turbine is investigated by applying various forms of foil, both symmetric and asymmetric, to obtain the appropriate foil profile. Symmetric foils were represented by NACA 0012, NACA 0018, and NACA 0021, while asymmetric foils were represented by NACA 4312, NACA 4512, and NACA 4712 foils. Simulations were performed using QBlade software, which was developed based on the DMST theory. In general, symmetric foils have a more stable performance than asymmetric foils because they produce a better performance at positive and negative angles of attack. This result is also supported by a review of efficiency and self-starting capability where symmetric foils have significantly higher CP values and positive CQ along the azimuth angle than asymmetric foils. Finally, NACA 0021 foil is recommended for a humpback whale fluke turbine based on its efficiency and self-starting capability.
As one of the coastal structures, breakwaters are built to protect the coastal area against waves. The current application of breakwaters is usually conventional breakwaters, such as the rubble mound ...type. Climate change, which causes tidal variations, sea level height, and unsuitable soil conditions that cause large structural loads, can be solved more economically by employing floating breakwater. In this study, numerical simulations will be conducted by exploring the optimum floating breakwater notched shapes from the Christensen experiment. The comparison of three proposed floating breakwater models, such as square notch (SQ), circular notch (CN), and triangular notch (VN), is compared with standard pontoon (RG) to optimize the transmission coefficient value is analyzed. Numerical simulations are conducted using Computational Fluid Dynamics (CFD) based on the VOF method with Flow 3D Software. Compared to the experimental study, the RG model's validation shows a good result with an error rate of 8.5%. The comparative results of the floating breakwater models are found that the smaller the transmission coefficient value, the more optimal the model. The SQ structure has the smallest transmission coefficient of 0.6248. It can be summarized that the SQ model is the most optimal floating breakwater structure.
Perairan barat Provinsi Lampung merupakan salah satu lokasi yang diperkirakan memiliki potensi energi gelombang yang cukup besar. Namun, minimnya informasi tentang titik potensial energi gelombang ...laut yang lebih rinci membuat kawasan ini belum dapat dieksplorasi dengan baik. Penelitian ini bertujuan untuk mendapatkan tinggi gelombang signifikan (Hs) yang merupakan salah satu variabel utama dalam menentukan energi gelombang laut di perairan barat Provinsi Lampung. Studi ini dilakukan melalui pemodelan numerik menggunakan model SWAN pada software Delft3D-WAVE dengan input model gelombang yang bersumber dari data ECMWF-Era 5 di laut lepas. Hasil pemodelan numerik menunjukkan gelombang signifikan terbesar terjadi pada musim barat dengan nilai 1,25-2,975 m. Sedangkan tinggi gelombang signifikan terkecil terjadi pada musim timur dengan nilai 0,941-2,079 m. Verifikasi hasil tersebut terhadap data AVISO menghasilkan nilai MAPE sebesar 16,355%, koefisien korelasi sebesar 0,8691, RMSE berkisar 0,277 m yang menunjukkan validasi yang baik dan memuaskan.
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