Estimating the coastline or shoreline is one of the crucial components in determining coastal accretion and erosion and in analysing coastal morph dynamics. In recent years, the socioeconomic ...pressure has increased on the Sidi Abdel Rahman coast area with the impact of climate change, which has led to the destabilisation of the coast. Therefore, this study aims to investigate the shoreline changes along the coast in the study area using remote sensing data for the period 2007 to 2021, modeling the shoreline change through the study area, and predicting shoreline change in the period from 2021 to 2024. It also suggests the type of protection required for the area from waves and sea currents.
Efforts to reduce emission of toxic gases into the atmosphere by sea transportation have been consistently carried out by the International Maritime Organisation (IMO) since 2009. IMO has introduced ...a regime known as energy efficiency design index (EEDI) to monitor and quantify the emission of CO2 because of its global climate impact. A comparison was conducted between trimaran hull forms without and with Axe-Bow on the main-hull with S/L=0.3 and 0.4, as well as a comparison with a monohull of comparable displacement. The CFD method was used to analyse resistance. Overall, the trimaran without the Axe-Bow can decrease resistance by 22.6%, while the trimaran with the axe-bow can reduce resistance by 25.0%. Additionally, this resulted in a 54.8% decrease in EEDI on trimarans without axe-bow and a 55.4% reduction on trimaran equipped with axe-bow when compared to MV Sabuk Nusantara 104. In addition, despite little difference between trimaran with and without axe-bow, the introduction of axe-bow has shown apparent benefits to lower EEDI.
Power reduction is the central goal to maximize cruising duration of tourist underwater vehicles (UV) that can be achieved by shaping the hull. So, in this paper, hydrodynamic force of resistance of ...the tourist UV’s bare hull is analysed. A numerical model based on Computational Fluid Dynamics in OpenFOAM is developed to simulate the longitudinal movement of an UV in a viscous and incompressible fluid for the infinite water depth. Three head geometries, including both spherical heads (S-S), spherical bow and elliptical stern head (S-E), and UV with both elliptical heads (E-E) are compared. At the first step, the effects of the length-to-diameter ratio and forward speed is studied for the S-S UV. The mesh size is calibrated using Grid Convergence Index, provided by ASME, while the model validation is based on the results for cube and sphere as well as by comparison with resistance coefficient of a SUBOFF bare hull. S-E and E-E UVs are then analysed for typical length-to-diameter ratio, comparing their force of resistance to the S-S type. The elongated elliptical heads are in many cases found favourable compared to the spherical heads. The results of this study may be useful for the conceptual design of tourist UV and for verification of the complex numerical models that are necessary to account for the influence of appendages on the force of resistance of such innovative UV.
Recently, an increasing attention is given to preservation and popularization of Croatian traditional boat building, which plays an important role in Croatian cultural and national heritage. ...Reconstruction and revitalization projects of individual historical vessels are key factors within preservation process, where the lack of technical documentation is one of the main issues. In this paper, a simple and efficient procedure for taking offsets of a traditional fishing vessel guc is presented to document and preserve the traditional Croatian vessel form. A 3D model of a guc is generated using the points on the hull surface obtained by the manual measurement and a fairing process. Numerical simulations of the resistance test for a fishing vessel are carried out for a wide range of speeds, and the curve of effective power as a function of vessel speed is provided.
Ovaj rad predstavlja termodinamičku energijsku i eksergijsku analizu te usporedbu dviju propulzijskih parnih turbina na temelju njihovih radnih parametara iz eksploatacije. Prva turbina ne posjeduje ...pregrijavanje pare i ima samo dva kućišta (visokotlačno i niskotlačno kućište), dok druga turbina posjeduje pregrijavanje pare i ima jedno dodatno kućište (srednjetlačno kućište). U literaturi se trenutačno ne može naći izravna i egzaktna usporedba ovih dviju brodskih parnih turbina i njihovih kućišta bazirana na stvarnim eksploatacijskim parametrima. Uz analize energije i eksergije, u istraživanju ispituje se osjetljivost parametara eksergije u odnosu na izmjenu temperature ambijenta za obje turbine i svako kućište. Takoder je prikazan utjecaj procesa pregrijavanja pare na energijsku i eksergijsku iskoristivost čitavoga postrojenja. Za obje promatrane turbine i njihova kućišta vrijedi da su relativni gubici i iskoristivost (energije i eksergije) obrnuto proporcionalni. Djelovanje srednjetlačnog kućišta parne turbine sa pregrijavanjem pare najbliže je optimalnom. Zbog različitih izvora gubitaka pri energijskoj i eksergijskoj analizi, svaka analiza detektira različita kućišta turbina kao najproblematičnija. Proces pregrijavanja pare smanjuje gubitke i povećava iskoristivost (energije i eksergije) svakoga kućišta i cijele turbine. Cijela turbina s pregrijavanjem pare ima energetsku iskoristivost koja je jednaka 81,46% i eksergijsku iskoristivost koja je jednaka 86,48%, dok cijela turbina bez pregrijavanja pare ima energijsku i eksergijsku iskoristivost koja je jednaka 76,47%, odnosno 80,94%. Eksergijski parametri parne turbine bez pregrijavanja pare, kao i njezina kućišta pod većim su utjecajem promjena ambijentalne temperature u usporedbi s parnom turbinom sa pregrijavanjem pare i njezinim kućištima. Proces pregrijavanja pare povećat će iskoristivost cijeloga pogonskog postrojenja u stvarnim eksploatacijskim uvjetima u iznosu od 10% do 12%.
The SPS application in ship structure is an innovative breakthrough that provides an excellent strength-to-weight ratio. SPS application for new construction is crucial to ensure the proposed design ...has better static and dynamic behavior than conventional design. The study aims to evaluate the weight savings and dynamic characteristics of different proposed framing systems of 155 m barge due to the application of various SPS types in the deck, ship hull, and bottom structures. A total of three proposed construction systems: longitudinal, transverse, and mixed framing systems, are investigated under different plate configurations, material types, and scantling sizes. In addition, the free vibration analysis is used to evaluate the influence of damage occurrence on the structural characteristics. Several damage parameters, including damage size, location, shape, and depth, are investigated using ABAQUS software. The promising result of weight saving indicates SPS application results in about 9-13%. Moreover, the debonding assessment reveals that eigenvalue decreases with increasing debonding size, where the damaging effect in higher modes is more substantial. The stiffness loss due to debonding causes a high local deformation in the debonded area. Moreover, interfacial debonding reduces eigenvalues significantly, particularly in localized debonding shapes. It can be found that several damage parameters, including damage size, location, depth, and shape, influence the eigenvalue shifts.
The electric ship propulsion system due to its economic advantages and, first of all, better mechanical properties than internal combustion engines (influence on ship manoeuvrability) have gained ...popularity in recent years. This paper presents an investigation of a series hybrid electric propulsion system where two sources of power are used: a permanent magnet synchronous generator and energy storage battery to supply electric propulsion system, which is a permanent magnet synchronous motor. Controlling the power flow from multiple power sources in a series hybrid mechatronic system is important to increase the energy efficiency of the propulsion system. Developing a suitable power flow control method is difficult due to the nonlinear nature of the power sources in the series system. In this paper a method of energy optimization of the system has been verified which allows to improve energy efficiency by reducing reactive power in the system. In this paper, an analytical study of the mechatronic system of a serial hybrid electric ship propulsion system is carried out based on the analysis of the steady-state electromagnetic and energy relations. The proposed control with energy optimization was compared with the commonly used FOC control. The analytical studies have been confirmed by performing simulation studies in Matlab-Simulink program. The proposed optimization method allows its use not only in ship electric drives but also in other autonomous electric drives using the series topology of the hybrid system.
Confidence levels of the seakeeping experiment results can be assessed through uncertainty analysis. The seakeeping experiments with a free-running model system were carried out in the manoeuvring ...and ocean engineering basin (MOB) at the Indonesian Hydrodynamic Laboratory (IHL) using uncertainty techniques to improve the experiment quality. The method used is the International Organization for Standardization, Guide for Uncertainty of Measurements (ISO-GUM), type A and B uncertainty, which is the foundation for the uncertainty analysis for seakeeping experiment recommendations released by the International Towing Tank Conference (ITTC). This research aims to determine the combined uncertainty value of the seakeeping experiment on a benchmark ship model with a scale of 1:62, representing the full scale of 186 meters. Seakeeping testing is carried out under head and beam waves, each with regular waves at one wave height (Hs) with three different wave periods (Tw). The experimental seakeeping result, generally, has the same tendency in each heave, pitch, and roll motion mode. The expanded uncertainty with 95% confidence level of the RAO-Heave uncertainty in all period conditions is always less than 3%, RAO-Pitch uncertainty in all period conditions is always less than 1%, and RAO-Roll uncertainty in all period conditions is always less than 1.2%. These uncertainties are quite small.
