Annals of ”Dunarea de Jos” University of Galati. Fascicle XI Shipbuilding

A comparative analysis of course keeping and turning circle for a 37000 tdw chemical tanker

2023-12-17T19:14:47+02:00

The manoeuvring characteristics of the ships represent a complex phenomenon, which includes their capacity for both maintaining a steady course and turning ability. There are no simple methods for evaluating a ship's performance in these aspects. Furthermore, the flow patterns connected to these phenomena are complex and frequently coupled with other factors. The purpose of this study is to evaluate the course keeping and turning performance for a 37000 tdw chemical tanker. Course-keeping is evaluated based on stability criteria, while empirical relations and numerical simulations using hydrodynamic derivatives from both empirical and computational fluid dynamics (CFD) methods are employed to analyse the turning circle and then compared with data from actual sea trials.

Estimation of linear hydrodynamic derivatives of a 37000 tdw chemical tanker using virtual captive model tests

2023-12-17T19:15:51+02:00

Forecasting the hydrodynamic properties of a ship is crucial for assessing its maneuvering capabilities. This study presents the results of static drift and circular motion simulations conducted on a 37000 tdw chemical tanker. The calculations were carried out using the ISIS-CFD solver, accessible through the FineTM/Marine academic license provided by NUMECA. The flow solution was obtained by numerically solving the Reynolds-Averaged Navier Stokes equations, employing the k-ω Shear Stress Transport (SST) model to represent turbulence. The simulation results were used to determine the linear hydrodynamic derivatives, which were then compared with hydrodynamic derivatives estimated with empirical formulas proposed by Clarke et. al. [1] and Tribon Initial Design module in the absence of experimental results.

On advanced global strength analysis of a pleasure yacht by user’s procedures implemented in FEMAP / NX Nastran

2023-12-17T19:18:49+02:00

The objective of this study is to analyze the global structural strength of a pleasure yacht by advanced FEA approach. This is accomplished by developing and implementing a user FEMAP API script for equilibrating the FEA ship model, in calm water and sagging and hogging wave conditions, for different wave design heights, up to a maximum height of 6.5 meters. The FEA strength is assessed by yielding stress and buckling criteria.

Ranking the main risks that can lead to the pollution of the marine environment in the Black Sea

2023-12-17T19:36:43+02:00

The aim of this paper is to present the way in which the main risks that can lead to the pollution of the marine environment of the Black Sea can be ranked using multicriteria analysis, based on the AHP process (Analytic Hierarchy Process). This analysis represents a solid basis for the decision-making process. Based on this hierarchy, the decisionmakers in the maritime field can easily visualize both the risk assessment criteria and the risks that must be taken into account. The analyzed risks (oil spills, shipwrecks, ship collision, fire explosion) in relation to the considered criteria (bad weather conditions, highdensity traffic, human errors, ship age) have been ranked as follows: "ship collision" risk with overall priority = 0.366 is the one that must be considered the most dangerous in relation to the considered criteria, followed in descending order by the risk of "oil spills"
with overall priority = 0.303, the risk of "shipwrecks" with overall priority = 0.181 and finally the risk of "fire explosion" with overall priority = 0.150.

Preliminary hydrodynamic analyses for a river research ship. comparative study of mono-hull and catamaran ship type

2023-12-17T19:38:50+02:00

The design in early stages of the ships involves several preliminary hydrodynamic analyses, also for the ship operating on river waterways, IN(1.2) navigation class. This technical paper includes two main parts as preliminary assessment for the design constructive versions of a river research ship. The first part is focused in the comparative study of the mono-hull and the catamaran ship design by seakeeping and global strength criteria. The second part is focused on the ship resistance for two mono-hull versions of the river research ship. The study hydrodynamic preliminary results are the initial bases for proper design in next steps of the river research ship.

The use of hydrogen on board ships

2023-12-17T19:41:00+02:00

Hydrogen, the carbon-free energy of tomorrow, is being explored as a potential fuel for ship propulsion. It is considered a clean and sustainable alternative to traditional fossil fuels, as it produces zero emissions when used in fuel cells or burned in engines. Hydrogenpowered ships have the potential to significantly reduce greenhouse gas emissions and contribute to decarbonizing the maritime industry. However, it is important to note that the adoption of hydrogen as a mainstream fuel for ships is still in the early stages, and there are various technical and infrastructure challenges that need to be addressed for its widespread implementation.

Wind propulsion of ships to decarbonize maritime transport

2023-12-17T19:46:31+02:00

The International Maritime Organization and the European Commission are demanding increasingly significant decarbonization efforts from shipowners, and maritime freight should be integrated into the EU emissions trading system. Several technologies exist for sail propulsion: the Flettner rottor, rigid panels made of composite materials, sails and in particular the kite, innovative in this field. Studies show that 3700 to 10700 ships could be equipped with sail propulsion systems by 2030. The release of 3.5 to 7.5 million tonnes of CO2 could thus be avoided in 2030. In this article, the fundamentals of the ship propulsion by the wind are presented: a credible, efficient technological proposition available today to ensure the sustainability of transport.

The influence of plating with flat bars around technological cutouts on the stress state of a 37500 tdw chemical tanker

2023-12-17T19:48:32+02:00

The purpose of this study is to determine the stress states of the plating around the technological cutouts of a 37500 tdw chemical tanker under normal operational conditions, taking into account the efficiency of operational optimization and structural strength increase. This study will assess the stress state in the double bottom region of the ship, which experiences the most significant external loads from hydrostatic water pressure and internal loads from cargo pressure.

Determination of stress state and deformations that can appear in tranversal frames of a 48309 dwt bulk carrier

2023-12-17T19:50:42+02:00

The main objective of this study case is to analyze the response in terms of stress and deformation of transversal frames of a bulk carrier that occur due to the applied loads. This assessment helps ensure the safety of the vessel in terms of structural strength and resistance and to determine the best solutions to apply in unfavorable scenarios. The analysis will be performed on a cargo tank, for three static stress cases, the vessel being placed on still water, on sagging and hogging.

Analysis of stress and deformations in the transverse walls of a 50100 tdw tanker

2023-12-17T19:58:01+02:00

The purpose of the stress and strain analysis study in the transverse walls of a 50100 tdw tanker is to assess the structural integrity of the vessel and identify potential problems or vulnerabilities as well as methods to improve the strength of the structure.

Comparative analysis of seakeeping methods: numerical, software simulation and experimental study

2023-12-17T20:04:12+02:00

The current study case presents a comprehensive comparison of seakeeping analysis methods, utilizing the seakeeping numerical analysis based on Lewis’s form description of a hull, Ansys Aqwa, and experimental data obtained from the towing tank of the Faculty of Naval Architecture in Galati. The primary objective of this study is to assess the accuracy and reliability of two numerical approaches in predicting the seakeeping performance of a vessel under varying conditions. The experiment was carried out under two scenarios, one with the model at zero speed and another with the model towed at 1.28 m/s and 180o heading angle. The diverse set of conditions aimed to simulate real-world scenarios and capture the dynamic nature of ship motions in waves. The employing of Lewis forms numerical analysis, Ansys Aqwa simulation, and experimental data, the results were compared and evaluated in terms of their accuracy and agreement.

Study case on the characteristics and performances of a propulsion system for a crude oil tanker

2023-12-17T20:09:56+02:00

This paper presents aspects regarding the analysis of the characteristics and performances of a propulsion system for a crude oil tanker. The study involved several steps: first, the ship’s resistance and the necessary propulsive power were calculated to choose and design the main components: engine, transmission and propeller; to obtain maxim propulsive efficiency at the desired speed, with low fuel consumption and reduced CO2 emissions. Four slow Diesel engines were selected and the optimal propellers were designed to analyse and adopt the more efficient solution. A number of factors were taken into account for ship propulsion system components selection such as: required power, revolution rate to ensure an optimal propeller diameter to be located behind the ship, the specific fuel consumption parameters, desired ship speed, etc.

Review of the atypical systems of slow-speed two-stroke marine engines

2023-12-17T20:16:12+02:00

This article provides a review of the varying systems of slow-speed, two-stroke marine engines. The paper begins with the operating principles of the typical two-stroke engine cycle employed in these engines, highlighting the intake, compression, combustion, and exhaust strokes. It then continues with defining and describing other unconventional systems rarely found on engines of different sizes and applications. The focus of the study case is on the systems that prevent pollution, as well as various other systems observed in larger marine engines.

Aluminum, an alternative to GRP for manufacturing of sports boats

2023-12-17T20:18:59+02:00

Pollution is being discussed more and more in the world. It is known that the production of Glass Fiber Reinforced Polyester (GRP) is a polluting process. Also, the implementation of GRP is a process that can cause various ailments to the personnel who apply it. Over time, boats made of GRP suffer degradation due to interaction with the environment: cracks, exfoliation of the outer layer of gelcoat, etc. These degradations must be remedied, operations that involve the application of substances that are also polluting. More and more traditional manufacturers of sports boats are replacing GRP with aluminum. This, although the process of obtaining it from the ore is not without toxic components, is less polluting and friendlier to the executors than GRP. In this paper, we seek to elucidate the advantages that aluminum has over GRP in the construction of sports boats.

Comparative static FEA of equipment foundations on marine vessels: standard, stiffened, and structural integrated

2023-12-17T20:27:37+02:00

This study case presents a comprehensive static finite element analysis (FEA) of an equipment foundation aboard a marine vessel, conducted in three distinctive scenarios. The initial analysis adheres to a generalized standard, providing a baseline for structural performance. Subsequently, the same foundation is re-evaluated with the addition of stiffening brackets, aimed at enhancing rigidity and load distribution capabilities. The final
analysis transitions from the theoretical models to practical application, examining the foundation as it is truly mounted and integrated within the ship's structure. Each scenario is meticulously compared to assess the impact of design modifications and integration on the foundation's performance.

Comparative analysis of the maneuverability performance of a chemical tanker with the power of the propulsion installation PB=6480kw

2023-12-17T21:05:57+02:00

This article investigates ship maneuverability by conducting and comparing calculations using two distinct computational platforms. The results obtained from these calculations are subsequently compared with real data from the sea trials. A detailed analysis of the discrepancies between theoretical and empirical results provides insights regarding the reliability and precision of each computational platform in assessing ship maneuverability in the naval domain. This research contributes to improving methods for evaluating ship performance and validating computational platforms used in the industry.

Comparative analysis of the manoeuvrability performance for a 9000 tdw chemical/oil tanker

2023-12-17T20:36:52+02:00

The concept of manoeuvrability is very important for efficient ship operation but also in ship safety. The aim of this paper is to test and perform a comparative analysis of manoeuvrability performance of a 9000 tdw chemical/oil tanker. The comparative analysis has been performed between the results obtained based from two software’s, namely PHP and MPP, but also between the results obtained in the sea trials with the output data from MPP. In this way it will be shown the differences (if any) in terms of manoeuvrability., and if the two used platforms are effective for providing preliminary determination of performances of manoeuvrability.

Design of a submarine main ballast blowing systems

2023-12-17T21:07:23+02:00

A submarine ballast system represents a combination of dedicated equipment and piping in which the main circulating fluid is either sea water straight from the submarine exterior or air which is compressed at high pressures and then it is stored in pressure vessels onboard. These fluids are, then, introduced in or extracted from various tanks located strategically onboard the submerged vehicle. Because water cannot be compressed and because of it’s density, it will require large amounts of energy and pumps to be able to move all the water within the system in a short period of time that is required for surfacing a submerged vehicle. Therefore, compressed air is favoured for the main deballasting because of the air’s capability of being stored at high pressures and displacing water in a fast manner once it is fed into the ballast tanks, thanks to it’s ability to expand as the submarine emerges and the surrounding water pressure drops. In addition, the compressed air systems must operate for at least a normal surfacing from periscopie depth, but also for surfacing from the maximum depth in the case of an emergency. From an engineering standpoint, ballast tank blowing systems are complex, but nevertheless are vital, for allowing the maneuvering of the submarine and it’s bouyancy within the water it navigates, regardless if it’s in a surfaced or submerged condition and must be done in the smoothest and with as little noise as possible. The requirements of designing and calculation of such systems are covered by the Class and Administration rules and regulations.

Design of a submarine main ballast tank flood and vent openings mechanisms

2023-12-17T20:46:38+02:00

Besides the piping systems used for blowing the main ballast tanks of a submarine by feeding compressed air, a great importance must be given to the flood and vent openings and the mechanisms that operate the covers. From an engineering standpoint, the flood openings must be as small as possible to minimize the noise generated by the water flow.Their number and cumulated area must be determied as to avoid over pressure when feeding compressed air into the ballast tanks that may lead to structural damage. The requirements for designing of such systems are covered by the Class and Administration rules and regulations.

Mounting and testing technology for a steering gear system with hydraulic cylinders

2023-12-17T20:48:48+02:00

The steering gear system is part of the group of vital installations for a ship. Its role is to ensure course stability and, at the same time, to facilitate the changes of navigation direction. In this context, the technology for assembling the system is well-defined through rules, procedures, and work instructions. A steering system that is correctly assembled according to the instructions and execution drawings will lead to proper operation and, at the same time, the successful completion of applicable steering system tests. The applicable tests for steering systems are depending to the type and purpose of the vessel. However, SOLAS defines a series of general high-level tests that must be performed, and during these tests, the quality of the installation is to be demonstrated. The present work will develop both the subject of the steering gear installation, which directly influences the results of the tests.

Assessment of motor yacht hydrodynamic performance

2023-12-17T20:52:12+02:00

This study presents a comprehensive Computational Fluid Dynamics (CFD) analysis of an 18-meter motor yacht featuring a trawler hull design with a swim platform. The investigation explores the hydrodynamic performance of the yacht across three distinct drafts and six varying speeds.

Effect of distance between the hulls variation on the total resistance of a catamaran

2023-12-17T20:54:23+02:00

The purpose of this study case is to assess the total resistance and investigate the fluid flow around a scale model catamaran varying distance between the diametral planes of the two hulls. This study is focused on accurately determining the total resistance encountered by the catamaran while it moves through water and, additionally, on understanding how the fluid flow behaves around the vessel with these design variables.

Study on the position of the bow spray rail of a patrol vessel

2023-12-17T20:55:57+02:00

Modern patrol ships characterised by an 'axe bow' shape allows the placement of an anti-spray rail. These not only reduce drag but also minimize the wave height generated by the ship's bow. This article will present the effect of positioning of an anti-spray rail at various heights on the ship's bow to reduce drag resistance. The most favorable placement scenario will be determined through the results of numerical simulations conducted by using the commercial software Fidelity Fine Marine.

Numerical simulation for predicting the respose of an offshore heavy lift barge in regular and irregular waves

2023-12-17T20:58:48+02:00

This study case concerns the prediction of the hydrodynamic response of an offshore heavy lift barge in the regular and irregular waves. The study focuses on predicting the six degrees of freedom responses for the barge in the operation condition when the ship speed is equal to zero, at various heading angles (0~180˚) and for several wave frequencies (0.02~2.0 rad/s). The numerical simulation is carried out using the 3D diffraction /radiation motion solver Hydrostar software that is based on potential theory to predict the wave-body interactions. All the hydrostatics, loading and sailing aspects are initially estimated, and then introduced as an input in the simulation process corresponding to the ship speed and heading directions. For the irregular sea simulations, the ITTC spectrum is used to describe the wave for a generic study case in the Black Sea to make the study feasible for offshore applications in operational conditions where the ship speed is equal to zero.