Analisis Wave Resistance Pada Kapal Selam Tanpa Awak (Remotely Operated Vehicle)

Penelitian ini memaparkan perhitungan hambatan gelombang yang dibangkitkan oleh kapal selam tanpa awak yang besarnya dipengaruhi oleh posisi operasi wahana terhadap permukaan air (free surface). Ada empat posisi kapal selam tanpa awak ini terhadap permukaan air yang dievaluasi yaitu terapung, snorkeling, submerged 0.5 m, dan submerged 1 m. Tent Function, Michlet Code dan CFD dikembangkan untuk mengevaluasi besarnya hambatan gelombang dalam empat kondisi operasi dan lima variasi kecepatan. Hasil evaluasi terhadap kapal selam tanpa awak dengan panjang 2 m dan diameter 0.25 m menjelaskan bahwa semakin dalam posisi wahana dari permukaan air maka semakin mengecil nilai hambatan gelombang pada seluruh nilai froude number. Pada kedalaman 0.5 m dibawah permukaan air besarnya hambatan gelombang menurun 64 % dari kondisi wahana saat mengapung, dan semakin besar nilai prosentasi penurunannya saat beroperasi di kedalaman 1 m yaitu rata-rata sebesar 74 % untuk semua nilai froude number. Persentase tingkat kesalahan pada semua variasi untuk kondisi terapung 3.29%, kondisi snorkeling 4.3 %, kondisi submerged 0.5 m 10.01 %, kondisi submerged 1 m 15.05 % untuk metode Tent Function dan Michlet Code, kemudian untuk metode Tent Function dan simulasi CFD pada kondisi submerged 0.5 m 13.22 % dan kondisi submerged 1 m 16.34 %. ================================================================================================================================= This study describes the calculation of wave resistance raised by drone submarine. It is influenced by the position of a vehicle operating on the water surface (free surface). There are four positions of drone submarine operating that evaluated. They are snorkeling, submerged 0.5m and submerged 1 m. . Tent Function, Michlet Code dan CFD were developed to evaluate the magnitude of wave resistance in the four operating conditions and a five speed variations. The evaluation results of drone submarine with a length of 2 m and a diameter of 0.25 m indicates that the deeper position of drone submarine from the water surface become smaller wave resistance values on the entire value of the Froude number. At a depth of 0.5 m below the water surface, The value of wave resistance decreased 64% from floating condition, and the greater the percentage decline value while operating at a depth of 1 m which is an average of 74% for all Froude Number. Number of percentage error for all variations are 3.29 % for floating condition, 4.3% for snorkeling condition, 10.01 % for submerged 0.5 m, 15.05 % for submerged 1m that based on Tent Function and MichletCode. Number of percentage error for all variations are 13.22 % for submerged 0.5 m, 16.34% for submerged 1 m that based on Tent Function and CFD

Equivalent Single Layer Approach for Buckling Analysis of Stiffened Panel Under Bi-Axial Compression and Lateral Pressure

Ship structure composed of stiffened plates is subjected to a variety of loading conditions during service, which can lead to buckling. As a result of panel buckling, the overall strength of the ship hull girder is reduced, which is what determines the ultimate strength of the hull girder. The ultimate strength analysis can be accomplished with finite element (FE) simulation, but detailed modeling can be time-consuming. Due to these reasons, it is more advantageous and costeffective to replace the three-dimensional (3D) stiffened panel model with a two-dimensional (2D) equivalent single layer (ESL) plate. This shift from 3D to 2D is premised on the accuracy of ESL in representing the various buckling modes of stiffened panels, which are determined by panel topology and boundary conditions. Therefore, an equivalent single layer plate (ESL) that represents a stiffened panel is evaluated in different buckling modes. Considering that ESL is asymmetric in nature, any modification of the stiffened panel's geometry has a significant effect on the buckling modes. In this paper, we are concerned with two modes of buckling: (i) local buckling within the stiffeners of the plate and web, and (ii) local lateraltorsional buckling within the stiffeners. According to the results, ESL is capable of accurately predicting the effect of local buckling in combination of biaxial compression and lateral pressure

Desain Self-Propelled Barge Sebagai Fasilitas Pengangkut Block untuk Galangan Kapal dari Batam ke Singapura

Salah satu jasa yang disediakan oleh galangan-galangan kapal di Batam dan Singapura adalah layanan pembuatan blok-blok kapal ataupun bangunan offshore  dimana blok tersebut akan difabrikasi di sebuah galangan lalu diantar ke galangan lainnya untuk kemudian dilakukan joint erection. Dalam tugas akhir ini akan dibahas sebuah moda transportasi berbentuk self-propelled barge yang berfungsi untuk mengangkut blok-blok tersebut dengan tujuan meringankan biaya produksi yang disebabkan oleh penyewaan tongkang beserta tugboat.  Analisis teknis yang dibahas yaitu penentuan ukuran utama kapal, koefisien bentuk, hambatan dan propulsi kapal, freeboard, stabilitas kapal, trim, serta prosedur loading dan off-loading. Serta perhitungan ekonomis yang dibahas yaitu perhitungan biaya pembangunan kapal, penentuan harga sewa kapal, break even point, serta perbandingan harga dengan moda transportasi yang sudah ada. Ukuran utama kapal yang didesain yaitu panjang per pendicular (LPP): 89,2 meter, lebar (B): 21,1 meter, sarat (T): 2 meter, dan tinggi (H): 4,3 meter, dengan kecepatan : 10 knots. Kapal ini memiliki kapasitas untuk mengangkut tiga blok bangunan kapal ataupun bangunan offshore  yang memiliki ukuran maksimal luasan tiap blok 20 x 18 meter dan berat maksimal 270 ton. Harga penyewaan self-propelled barge ini adalah Rp.6.700.000.000

DUBINA PROMJENE TERMOKLINA NA OTOKU SUMBA NA TEMELJU PLANKTONSKIH SKLOPOVA FORAMINIFERA I NJEGOVE IMPLIKACIJE NA EUTROFIKACIJU OD POSLJEDNJE DEGLACIJACIJE (~ 18 ka BP): PRELIMINARNA STUDIJA

Changes of the thermocline depth (DOT) at the Sumba Island offshore are not well-known compared to the DOT changes in the Timor Sea, the main exit passage of the Indonesian Through-flow (ITF). Planktonic foraminiferal assemblages in cores collected from the southwest Sumba offshore (ST08) and Sumba Strait (ST12, ST13, and ST14) were used as a tool to infer the DOT and paleoproductivity changes at the Sumba Island offshore. The DOT changes were indicated from the thermocline and mixed layer dwellers’ relative abundance while the paleoproductivity changes were indicated from the relative abundance of Neogloboquadrina dutertrei. This study suggests a contrast between the DOT pattern at the Sumba Island offshore and the DOT pattern in the Timor Sea during the Last Deglaciation–Holocene. The contrast DOT pattern indicated that the multi-millennial changes of the Australian-Indonesian monsoon (AIM) during the Last Deglaciation– Holocene were the main factors behind the DOT changes in this region while the effects of El Niño Southern Oscillation (ENSO) –like, Indian Ocean Dipole (IOD) –like, and ITF to DOT changes were minimal. Paleoproductivity enhancement at the Sumba Island offshore was not solely related to the monsoon-driven coastal upwelling intensification, which resulted in the DOT shoaling and eutrophic condition. The increase of nutrient availability in surface water due to river runoff increase and changes in the lifted water mass nature were also able to enhance productivity in this region.Područje ispitivanja nalazi se uz otok Sumba, a promjene dubine termokline (DOT) u ovoj regiji nisu dobro poznate u usporedbi s Timorskim morem. Zajednice planktonskih foraminifera korištene su za prepoznavanje DOT-a i promjene paleoproduktivnosti u jezgrama prikupljenim s jugozapadne Sumbe (ST08) i iz tjesnaca Sumba (ST12, ST13 i ST14). Ova studija sugerira da su tisućljetne promjene u režimu australsko-indonezijskoga monsuna (AIM) bile glavni čimbenik DOT promjena na jugozapadu Sumbe i tjesnaca Sumba nakon posljednje deglacijacije, što je stvorilo suprotne uvjete u odnosu na Timorsko more. Učinak poput južnih oscilacija El Niño (ENSO) i dipola Indijskoga oceana (IOD) sličnih DOT promjenama naznačen je samo oko kasnoga holocena, dok su promjene indonezijskoga protoka (ITF) utjecale samo na istočni tjesnac Sumba oko srednjega i kasnoga holocena. Produbljavanje termokline usko je povezano s poboljšanjem AIWM (AISM), El Niñom (La Niñom) i pozitivnim (negativnim) IOD-om. Poboljšanje paleoproduktivnosti nije bilo povezano samo s jačanjem DOT-a, već i s većom dostupnošću hranjivih sastojaka zbog povećanoga donosa slatke vode rijekama. Promjene u prirodi podignute vodene mase također su utjecale na promjene u paleoproduktivnosti

The wave making resistance prediction of a mini-submarine by using tent function method

This paper describes the wave making resistance solution of a mini submarine operating in under water surface with different level depth. The Thin ship theory was adopted to solve the problem for a case of the slenderness body. The source distribution along the centre plane of the body was expressed in Green’s function of Havelock source potential under water surface. The Tent function method was proposed to illustrate the hull form based on offsets data, and to solve the Michell integral problem numerically. Four operational conditions were performed i.e. floating, snorkelling, and diving with 0.5m and 1m under water surface. The computational results for the mini submarine with length of 2m and diameter of 0.25m explained a more deeply operated under water surface cause to decrease a value of wave making resistance for all cases of Froude numbers. While in the diving conditions of 0.5m and 0.1m under the water surface, the wave making resistance were resulted about 64% and 74% less than the case of floating condition respectively. Furthermore, the effect of vertical fin on the body was investigated, where the wave making resistance could increase average 7.2% in snorkelling, 11.4% in 0.5m diving, and in the 1m diving about 9.07% for all Froude numbers. Over all the results of this approach shown a good agreement with the results come from Mitchell code

Design and Construction of Spud Housing for Floating Dock

A floating dock is a type of pontoon for dry docking ships, possessing floodable buoyancy chambers. The Floating docks have more advantages than the other type of ship docking for maintenance. The purpose of the research study is to design and calculate of spud housing construction for floating dock. The spud housing is used to keep of floating dock in the safe condition. Mild steel material is used to construction of spud housing with yield point 235 x 106 N/m2. Design calculations were done by finite element analysis (FEA). The minimum stress is 1042.36 N/m2 and minimum deflection is 0.447 mm. The maximum stress is 0.142 x 109 N/m2 and maximum deflection is 4.019 mm. The maximum stress is not more than yield point of material

Reduction Of Outrigger Wide To Maximize Fishing Boat Landing Area Capacity In Prigi Fishing Port

Jukung fishing boats, prevalent in Prigi, face challenges due to their wide design (approximately 5 meters on both sides). This excessive width often necessitates berthing further from the coast. To address this issue, this study investigates the feasibility of reducing outrigger width to increase berthing capacity at PPN Prigi while ensuring vessel stability. Through a systematic analysis of various outrigger widths (1.5, 1.25, 1, and 0.75 meters), the study determined that a reduction to 1 meter maintains vessel stability as per HSC 2000 Annex 7 and Annex 749 (18) Ch3 design criteria. A 1-meter reduction in outrigger length can increase berthing efficiency by 66% for a standard 15-meter berth with 30-40 cm ship spacing. Consequently, the east dock of PPN Prigi can accommodate an additional 94 jukung vessels, raising the total capacity from 142 to 236. This research provides valuable insights for optimizing port infrastructure and enhancing the operational efficiency of the fishing community in Prigi