No abstract

Indonesian Navy continues to build 60 Meter Fast Missile Boat (KCR-60) is one of them and acts as a fast patrol boat and high-speed combatant ship in the archipelago warfare. The bow of the ship is an important part in the design of the ship as well as the bow of the KCR-60, because it is the most stressed, stressed from the waves, with the bow design that has a bow profile like an axe, the slender shape of the waterline is able to reduce the impact waves, increase the efficiency of the inflow rate, reduce the resistance of the vessel received so increase a better speed. This study changed the design of the Conventional Bow KCR-60 into the Axe Bow design concept with numerically calculated the total resistance of the Bow Bow design using the Holtrop method and performed a comparative analysis with the computing program MARIN DESPPC 1999 and Maxsurf Resistance V8i software. The results of this study found the total resistance value of KCR-60 Axe Bow type at 28 Knots speed was 364.2 KN and Conventional Bow type was 374.5 KN, the difference was 10.3 kN or 2.75% smaller than the Conventional Bow type in the analysis comparison of Maxsurf Resistance V8i software. For comparative analysis of the MARIN DESPPC 1999 program the total resistance value of the KCR-60 Axe Bow concept at 28 Knots is 283.6 KN and the Conventional Bow type is 288.1 KN, the difference is 4.5 KN 1.56% smaller than the Conventional type.

Experimental uncertainty and measurement, particularly in engineering, have been increasingly emphasized over the last 20 years. Uncertainty analysis of ship model testing in seakeeping experiments based on International Organization for Standardization, Guide for Uncertainty of Measurements (ISO-GUM), report with recommendations published by ITTC (2008). In this paper, the uncertainties for free-running tests were performed for a model scale 1:62 as a benchmark model test at the Indonesian Hydrodynamic Laboratory (IHL). The benchmark model is representative of a full scale of 186 meters. The model has full appendages as well as a rudder and propellers to allow for free-running tests, natural roll period, free roll decay, and swing tests. Factors of basic uncertainty (type A and type B) are estimated using model tests. The standard deviation of the mean value of a repeated measurement is uncertainty type A. However, Type B uncertainty is estimated from manufacturing specifications. The uncertainty components resulting from both types are quantified by standard deviations. The uncertainty value of Type B is approximated by a corresponding variance. This study helps to understand the underlying uncertainty associated with this research, which resulted in a total geometry uncertainty value (Lpp, B, T, H, KG ¯ , and kyy) of 0.17598% and the total uncertainty value of the instrument calibration results (wave height sensor and qualysis motion tracking) is 0.01161%. The results of this study are expected to minimize the impact of sources of uncertainty and allow the potential for underlying uncertainty to be corrected for the next seaworthiness test.

Roll damping sangat berperan penting pada maksimum roll terutama pada daerah resonansi disekitar roll natural period. Dalam prediksi gerak roll, prediksi roll damping dilakukan dengan metode difraksi radiasi yang menambahkan viscous roll damping dari formulasi semi empiris maupun dari uji roll decay. Pada uji roll decay akan didapatkan koefisien komponen roll damping linier dan quadratik yang selanjutnya diperlukan dalam perhitungan nilai roll damping. Nilai koefisien roll damping ini bisa diperoleh dengan melakukan fitting hasil uji roll decay dengan metode Froude maupun Bertin. Pada studi ini dilakukan analisa terhadap perubahan roll damping dan akibatnya terhadap gerak roll pada dua buah model FPU barge yang identik namun berbeda dimensi. Perubahan dimensi model benda apung akan menimbulkan perubahan pula pada karakteristik koefisien linier maupun quadtatik roll dampingnya. Dari hasil pengujian model diketahui bahwa pengurangan dimensi panjang model dengan posisi relatif titik berat dan jarijari girasi roll tetap akan menaikan nilai koefisien roll damping 21% dari desain induknya. Kenaikan nilai koefisien roll damping didominasi oleh komponen linier. Dengan adanya kenaikan koefisien roll damping pada model yang lebih pendek menyebabkan turunnya nilai respon gerak roll melalui uji seakeeping.

Investigation of hydrodynamic interaction between the vessel and the seabed when entering shallow water is considered one of the most critical considerations of inland waterway transport. There are many investigations into the behavior of ships in restricted waters, such as ships traveling in different forms of canal cross-sections. The present study aims to evaluate the hydrodynamic interaction of the 750 DWT Perintis Ship moving through the different canal types to determine the relative effects of limiting the width and depth cross section on the ship's resistance. Two different canals with different cross sections, including canal bank and rectangular canal, were evaluated to investigate the influence of canal width (Wb), depth ratio (hw/T), and blockage ratio function (As/Ac). The Computational Fluid Dynamic (CFD) method with Reynolds-averaged Navier–Stokes (RANS) solver and turbulent model 𝑘−𝜀 were used to predict the total resistance of the ship. The proposed numerical simulation was initially validated with an experimental towing tank test in the error range of 0.11-7.74%. The results indicated similar phenomena were found both in rectangular and canal banks. The case with a shallower (lower hw/T) and a narrower (lower Bc/Bs) canal dimension has a higher resistance value. Backflow and subsidence of free surface became significant around the ship's hull in more restricted water, changing the ship's hydrodynamic characteristics and increasing resistance. It can be found that the higher the blockage ratio (mb), the higher the total resistance value in both canal types, which proved that ships with higher speeds were more sensitive to changes in waterway restrictions.