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

Survey and rehabilitation of the dry-dock main floating gate

Ovidiu Ionaș — 2025-12-13

The paper is a theoretical and practical approach to the uncommon way of rehabilitation of the dry-dock main gate of Damen Shipyards Galați. Most of the water tight system of the gate being under water and considering the improper condition of work in the Danube water, the taking out of the gate bottom became a must. The applied method considered the gate inclination of about 90° under floating status by particular actions based on
theretical calculation.

Comparative natural global vibration modes analysis of two gas carrier maritime ships

Leonard Domnișoru — 2025-12-13

This technical paper presents a comparative study of two gas carrier maritime ships, focusing on their natural global vibration characteristics. The selected ships are an LPG carrier with a length of 125.6 m and an LNG carrier with a length of 289.3 m, both of which have fully developed structural models, previously used for strength assessment analysis. For both ships, relevant loading conditions are selected, full cargo and ballast cases. The natural global vibration analysis provides the vertical, horizontal, torsional, and longitudinal eigenmodes, with or without the inclusion of the fluid-structure effect. The results emphasize the sensitivity and the differences in the two ships’ structures on the modal vibration characteristics.

Offshore platform adaptation to climate change through technological optimization and advanced monitoring

Cristina Alecsa — 2025-12-13

Climate change is one of the major challenges of the 21st century for the off shore oil industry, generating fundamental changes in operating conditions and requiring complex technological adaptations. This paper investigates the vulnerability of offshore oil infrastructures to the effects of climate change, analysing the impact of temperature increases, sea level changes and the intensification of extreme weather events on offshore platforms. By analysing the specialized literature and evaluating the data, the study identifies the main risks to which these infrastructures are exposed and proposes integrated optimization and adaptation strategies. The results highlight the need to implement advanced structural monitoring technologies, develop multi-criteria optimization methods and integrate renewable energy solutions to increase the resilience of offshore platforms. The analysis shows that infrastructure in Arctic regions is exposed to risks caused by permafrost instability, and many major European terminals are vulnerable to sea level rise. Our paper proposes a unified conceptual model that integrates structural optimization technologies, continuous monitoring solutions, and modern risk management approaches to maintain the safety and sustainability of offshore operations under conditions of intensifying climate change.

Composite materials used for kayaks

Alexandra Madalina Bujor — 2025-12-13

Composite materials are quite popular in kayak construction, especially for the hull of the boat, offering a number of advantages over traditional materials. Composite kayaks are those made from resin-impregnated laminates of fiberglass, aramid fibers, carbon fiber, or a mixture of these and other high-tech synthetic fabrics.

Floating production storage offloading concept

Alexandra Madalina Bujor — 2025-12-13

This article explains the advantages of Floating Production, Storage, and Offloading vessels, recent trends in mooring systems, hull construction, safety, and operational aspects. These types of vessels are vital to the modern offshore oil and gas industry. These specialized ships are designed to process and store hydrocarbons from offshore oil fields and of fload them to shuttle tankers or pipelines. Their adaptability and mobility make them especially valuable in deepwater and remote locations. These vessels, converted or specifically built for oil production, represent a significant evolution in the offshore extractive industry, offering a set of operational, economic, and strategic advantages that have positioned them as preferred options in numerous projects around the world.

Yacht design in the era of digital transition

Lucica Iconaru — 2025-12-13

The design of ships has changed dramatically since the 1970s. We have shifted from manual drafting to digital tools and computers, mostly because computer technology has greatly improved. Now, with the growth of smart digitalization in Industry 4.0, using modern digital software and tools makes ship design more efficient and enhances its quality throughout a ship's entire lifespan. However, this shift has also made operations more complex and requires users of the software to have more specialized training. Today, technologies like automated optimization, simulation-based design, managing the entire product lifecycle, digital twins, and artificial intelligence are commonly used in the shipping industry. These technologies are applied during both the design and construction phases, as well as in preparing and inspecting ships. This paper reviews major advances in these areas and discusses how the industry can address current and future challenges.

The analysis of induced vibrations by propulsion system excitation of an 8000 tdw chemical tanker, by a FEM approach

Maria Erofei — 2025-12-13

Nowadays, the ships become larger and more flexible, requiring that their design be evaluated also according to the vibration criteria, being induced by the onboard propulsion system. The vibration onboard comfort addresses the conditions ensured for the humans, passengers, and crew, setting up the reference quality for living during navigation conditions. Also, excessive levels of vibrations can cause fatigue issues, damage structural elements, and also various ship’s equipment during exploitation. This paper uses in study an existing operating vessel, for a preliminary vibration analysis stage, by using the FEM approach for the natural modes and the propulsion system-induced vibrations.

Modal analysis of a 100449 tdw bulk carrier for the amidships cargo hold structure.

Elena Cristina Saltan — 2025-12-13

A modal analysis of the ships’ structures is requested at any design step to check the possibility of local resonance occurring with onboard systems and equipment. The main study objective is to perform a local modal analysis of the amishships cargo hold structure of a 100449 tdw bulk carrier. The numerical modal analysis is done by 3D-FEM models, and besides the cargo mass, the vibration hydrodynamic added masses are included. Different elements' mesh size selection is done, and the modal solution conver gence analysis is approached.

The amidship cargo holds structural response of a 158500 dwt oil tanker, on design waves

Maria Nicoară — 2025-12-13

A strength analysis of the ships’ structural parts under design equivalent waves became mandatory by rule requirements, providing the elements' structural response. The main objective is to evaluate the local combined with the global structural response of a 158500 tdw oil tanker. The strength analysis of partial extended FEM models has been conducted, including the amidships three oil cargo hold tanks. Considering the navigation restrictions, the study analyzes their impact on the amidships structural integrity of the oil tanker.

Resistance and powering prediction using AutoPower module of AutoShip software case study

Elisabeta Buzilă — 2025-12-13

In the preliminary design stage of displacement ships, assessing total resistance and propulsion power demand is critical, since variations in hull form parameters significantly influence propulsion efficiency and engine sizing. In this study, the AutoPower module of the AutoShip software suite is used for a monohull vessel and a catamaran with a symmetric hull, both having similar main dimensions. Resistance and effective power were computed
for a speed range between 0 and 22 knots using several empirical methods implemented in AutoPower, including Andersen/Guldhammer, Holtrop, van Oortmerssen,
Digernes/Cheng, and Fung. The results highlight significant variations between the methods, with effective power predictions at the service speed of 18 knots ranging from 3.5 kW (Holtrop) to over 20 kW (Digernes/Cheng). The originality of the paper lies in emphasizing both the usefulness and the limitations of empirical formulations in the preliminary design of ships. The study concludes that, although AutoPower provides a fast and practical framework for estimating power requirements, the choice of prediction method must be correlated with the ship type and hull characteristics, while validation through model tests in hydrodynamic towing tanks or CFD simulations remains essential to ensure reliability.

Analysis of global and local strength using 3D FEM models extended over 3 cargo holds of a 47600 dwt chemical tanker

Ștefan Iulian Rață — 2025-12-13

This study examines both the local and global structural strength of a 3D finite element model (FEM) representing the three cargo holds of a 47600-DWT chemical tanker. Vessels of this type require a detailed assessment of their structural behavior under extreme loading conditions as well as routine operational demands. The analysis of stress distribution and structural strength enables the identification of critical areas within the hull,
providing essential insights for enhancing the vessel’s structural integrity and overall performance.

Project management approach for HVDC topside: risk assessment analysis of spool manufacturing

Lavinia Crețu — 2025-12-13

This paper aims to present how the risk assessment is conducted and to explore the main risks that could potentially disrupt the production flow of piping spool fabrication. From a management perspective, risk assessment may act as a foundation for a successful project. However, if it is not solid, the consequences appear. For complex projects, as HVDC topside, the operational team must be aware of the effects of risks that occur, and before any measures are implemented, the team must be capable of anticipating them. As a starting point, through a brainstorming session, it was assessed using a qualitative analysis of the risks, the probability of occurrence, and the impact they could produce. The process is associated with a variety of risks, from small ones (for instance, human errors that can be corrected) to larger ones (quality defects, contaminated materials, timeline constraints, non-compliance with standards, and safety risks). The paper also includes strategies of mitigation and associated actions. Moreover, in this paper are included methods proposed for further in-depth analisys.

Practical design aspects for inland navigation vessels to operate on the Danube River between the ports of Passau to Sulina (km 2233 to km 0)

Robert Ionuț Iliescu — 2025-12-13

The article aims to line up the main design aspects that are to be accounted in the process of designing an inland vessel for navigating on the Danube River from Passau Port (at Km 2233) to Sulina (at Km 0). The design process itself is comprehensive and must comply with many regulations and Danube River environmental parameters, therefore, this article will offer an organized perspective about what must be considered depending on the type of vessel and specific navigation sector.

Importance of periodical examination and maintenance of propellers for ensuring seaworthiness of cargo vessels

George Ciprian Iatan — 2025-12-13

A vessel as defined by COLREG, is operating in international waters with the assumption that it complies with international conventions adopted by the Flag Administration where it has been registered. In this regard vessels are periodically evaluated by Classification Societies recognised by the Flag, which are confirming fitness for operation of the vessel hull, installation, machinery and equipment. This is also the case of the vessel`s propeller, a vital component responsible for moving the ship, thereby directly contributing to its sea worthiness. Propeller and Shaft are subject to periodical surveys, where different type of assessment is carried out in connection with the vessel age, CSSC Certificate cycle and operational parameters. Any malfunction of the propeller is to be identified in due time and to be rectified by approved procedures in order to avoid unwanted casualty in operation.

Aerodynamic study of a recreational vessel designed for navigation in the Danube Delta

Emanuel Miron — 2025-12-13

The paper presents a study on the aerodynamic influence of wind on the hull of a sailing vessel, analysed both without sails and in full sail configuration, at different wind speeds and angles of incidence, in order to determine its aerodynamic torsor. The methodology included 3D model
ling of the hull using Rhinoceros software, creating the lines plan, and building the physical model through printing and assembly. The resistance to forward motion was estimated using the Delft Series method, through tabular calculations in Excel and specialized software such as MaxSurf Resistance. The aerodynamic study itself was conducted in the naval wind tunnel, after calibrating the six-component balance and verifying the velocity distribution, with tests performed for the vessel both with and without sails, at various wind speeds and angles.

Effects of ship vibration from the point of view of marine life, crew and ship structure

Andrei Gaiu — 2025-12-13

In this paper, we are trying to analyse what excessive ship noise and vibration can cause from multiple points of view. First, from a biological point of view, we can observe that a lot of sea species are affected by the vibration caused by ships along the modern trade routes. Second from the construction point of view, we can see that bad engineering can lead to a lot of problems, later in the ship lifetime. And the last point of view we analysed is the crew, which can suffer a lot of health problems if the noise and vibrations regulations are not followed.

The influences of forces generated by wind against a ferry type vessel

Andrei Dobrinas — 2025-12-13

The advancement of innovative solutions in shipbuilding demands the ongoing enhancement of research infrastructure. Hydro-aerodynamic challenges related to fluid flow around ship hulls can be addressed using numerical and/or experimental methods. However, numerical results must always be validated through experimental model testing in specialized hydro-aerodynamic laboratories. To support such research, a wind tunnel was developed at the Faculty of Naval Architecture, “Dunărea de Jos” University of Galați, enabling the measurement of aerodynamic forces and moments, as well as the distribution of speed and pressure on the hull under wind action. This paper highlights the main types of problems that can be experimentally investigated in the aerodynamic tunnel and describes the specific experimental equipment used.

A study on EEDI and EEXI requirements and ship emission reduction strategies

Mihaela Amoraritei — 2025-12-13

As response to the growing pressure to reduce Green House Gases emissions from ships with detrimental effects on the environment and climate, the International Maritime Organization (IMO) has developed mandatory requirements and regulatory tools such as: Energy Efficiency Design Index (EEDI), Energy Efficiency Existing Ship Index (EEXI), Ship Energy Efficiency Management Plan (SEEMP) and Carbon Intensity Indicator (CII). The paper
presents o comparative study of EEDI and EEXI requirements, as a set of technical measures to improve ships’ energy efficiency and to reduce emissions in line IMO targets. The paper analysis the specific role of each index and how they together contribute to emissions reduction in the design and construction stages and through operational phases of the ship’s life.

Performance enhancement of marine inert gas generator with combustion

Dragoş Alexandru Saragea — 2025-12-13

The heat generated in the combustion inert gas generator (IGG) is usually discharged with the flue gas cooling water. This paper proposes a system for recovering part of the heat generated in the IGG and using it in an absorption chiller for advanced cooling of the inert gas. The thermodynamic analysis showed that for an IGG consuming 240 kg/h of marine gas oil, 132 kW can be recovered to drive a lithium bromide-water absorption chiller, which can cool the inert gas down to 15°C, a temperature at which the water vapor content of the inert gas is 12.79 g/m3, much lower than if the inert gas is cooled only down to 50°C (82.5 g/m3) as is done in most IGGs. By recovering waste heat, the quality of the inert gas is improved (humidity is reduced) without additional energy consumption.

Stress and deformation analysis of a modular floating dock with a 5000-ton lifting capacity

Adelin Tănase — 2025-12-13

This study investigates the global structural behaviour of a modular floating dock with a 5000-ton lifting capacity. Using the finite element method (FEM), the research assesses stress and deformation responses under different operational conditions-lightship, ballasted, and full-load, both in calm water and under wave loads. Identifying the vessel’s critical stress concentration zones, the study effectively evaluated these areas, providing targeted recommendations to optimize the vessel’s structure and improve its operational reliability.

Structural evaluation of a 1400 dwt inland navigation barge

Teodora Tămoanu — 2025-12-13

Structural Finite Element Method (FEM) analysis provides a solid basis for evaluating the structural behavior of ships and contributes directly to the identification of critical areas in terms of strength and design validation. Inconsistent and non-compliant design can result in operational risks, high maintenance costs, early degradation, or even structural collapse. The present study aims to evaluate the overall structural behavior of a 1400 TDW inland navigation barge under real operating conditions, during ballast and full load navigation, both in calm water and under design-equivalent wave loads. The wave height of 1.2m was considered as imposed by the navigation area. To enable an effective evaluation that accurately reflects the barge’s actual condition, the 3D FEM model represents the idealized structure of the barge with average element size of 200mm. The model equilibrium was achieved using Orca3D software. The results were assessed based on the Von Mises criterion and the maximum deformation values, allowing the identification of regions with increased risk in terms of structural strength.

Local structural analysys of potable water system foundation

Alina Descalui — 2025-12-13

This paper presents the local structural analysis of a steel foundation supporting the pumps of a potable water system installed on a 30,000 DWT Handymax bulk carrier. The aim is to evaluate the structural behaviour of the foundation under static and dynamic loads representative for shipboard service and to propose simple constructive improvements that enhance stiffness and vibration performance. The potable water system is briefly described, including design requirements, sizing of the pumps, hydrophore unit and heat exchanger. The support structure is modelled in 3D CAD and analysed using the finite element method in ANSYS Mechanical, considering the mass of the pump unit and excitation frequencies up
to 60 Hz. Three foundation variants are investigated: the initial design, a stiffened version obtained by adding local reinforcements and an alternative closed-section frame using rectangular hollow profiles. For each model, deformations and equivalent von Mises stresses are evaluated and compared with the yield limit of steel S235JR and with serviceability criteria from Eurocode 3. The results show that the optimized foundation with rectangular hollow sections significantly reduces maximum deformations and improves dynamic behaviour, without exceeding allowable stress levels. Recommendations for monitoring, maintenance and vibration isolation using spring-type anti-vibration mounts are also formulated.

Testing of the anchoring installation for seagoing ships

Daniel Grigori — 2025-12-13

The anchoring installation is one of the most important deck systems, ensuring the safe temporary positioning of a ship in roads, coastal areas or inland waters. Although its configuration may differ from one vessel to another, the design and testing procedures are strongly standardised by the rules of classification societies. This paper presents an overview of the construction and operation of ship anchoring systems and describes the main requirements for testing anchor windlasses, chain stoppers, anchors and associated equipment. The methodology includes factory acceptance tests of the windlass, verification of the electrical drive according to IEC 60034-1, on-board commissioning and sea trial procedures. Particular attention is paid to the performance criteria requested by class rules, such as continuous pulling capacity, short-time overload, hoisting speed, braking capacity and structural integrity of the chain stopper. A practical example of testing a multi-purpose anchor-mooring windlass built by a Romanian manufacturer is discussed, highlighting the measurement of torque, temperatures, rotational speeds and brake performance. The paper underlines the role of proper planning, documentation and coordination between shipyard, equipment manufacturer, Owner and Classification Society to achieve a safe and reliable anchoring installation.

Pathways to maritime decarbonisation: comparative insights of solar powered proven designs

Florin Barbu — 2025-12-13

The maritime industry, a significant contributor to global carbon emissions, faces mounting pressure to transition toward sustainable operations through the integration of renewable energy technologies. This study offers a detailed comparative analysis of two solar-powered vessels, MS Tûranor PlanetSolar and Energy Observer, with a focus on their proven design principles, energy systems, and contributions to maritime decarbonization. MS Tûranor PlanetSolar, the first solar-powered vessel to circumnavigate the globe, features a solar-only design powered by 512 m² of photovoltaic panels and a 1,350 kWh lithium-ion battery system. This configuration allows for zero-emission operations but presents limitations in scalability and energy autonomy.In contrast, Energy Observer combines solar panels, wind turbines, and hydrogen fuel cells, showcasing a hybrid energy system capable of producing and storing hydrogen through onboard seawater electrolysis. This approach significantly extends its autonomy and operational versatility, making it more adaptable to diverse environmental conditions. The study evaluates the energy efficiency, environmental impact, and scalability of these vessels, highlighting their role as benchmarks for sustainable maritime engineering. By examining their real-world applications and limitations, the research underscores the importance of hybrid renewable energy systems and optimized designs in accelerating the decarbonization of global shipping. These findings provide critical insights for policymakers, engineers, and industry stakeholders seeking to promote sustainable practices within the maritime sector.

Harnesing wind power in maritime shipping

Florin Barbu — 2025-12-13

The maritime sector, responsible for approximately 2.5% of global carbon dioxide emissions, faces mounting pressure to implement sustainable practices in line with international decarbonization goals. Wind energy has emerged as a promising solution, with innovative applications being explored to enhance fuel efficiency and reduce emissions. This study undertakes a comparative evaluation of two vessels—Vindskip and Pyxis Ocean—that integrate wind power through distinct technological approaches. Vindskip utilizes an aerodynamic hull design, functioning as a large airfoil to harness wind energy directly for propulsion. This innovative concept has the potential to achieve fuel savings of up to 60% and greenhouse gas emission reductions of approximately 80%. In contrast, Pyxis Ocean employs a wind-assisted propulsion system, utilizing rigid OceanWings sails as a supplementary energy source. This retrofitting approach enables fuel consumption reductions of around 30%, offering a scalable and practical solution for existing vessels. The comparative analysis examines these vessels across critical performance metrics, in cluding energy efficiency, emissions reduction, scalability, and technological maturity. Vindskip exemplifies a forward-looking design for next-generation maritime operations, while Pyxis Ocean demonstrates the feasibility of integrating renewable energy technologies into current fleets. The findings highlight the complementary roles of innovative vessel designs and retrofitting solutions in advancing the maritime industry’s transition to ward a sustainable and low-emission future.