Hasil untuk "Naval architecture. Shipbuilding. Marine engineering"

Florent Batisse, Malo Duportal, Céline Rémazeilles et al.

The possible incorporation of Al and Zn issuing from galvanic anodes in the calcareous deposit forming on carbon steel surfaces subjected to cathodic protection was studied via three methodological approaches. The calcareous deposits were analyzed by X-ray diffraction for phase composition and X-ray fluorescence spectroscopy for chemical composition. First, a calcareous deposit formed on the steel pile of a seaport installation, sampled far (2 m) from the closest galvanic anode, was found to incorporate a small amount of the pollutants present in the seawater (Zn, Ti, Cu). An in situ experiment performed at another seaport focused on the calcareous deposit formed on steel surfaces close to the anode. In this case, a small amount of Zn directly issuing from the anode was incorporated in the deposit. This amount remained low as it corresponded to Zn(II) species adsorbed on the surface of aragonite crystals. Finally, laboratory experiments were performed with Zn(II) and/or Al(III) chlorides (10⁻³ mol L⁻¹ each) added to seawater. With both Zn(II) and Al(III), a Zn(II)-Al(III) hydroxychloride precipitated in the bulk seawater. With only Al(III), and under a higher cathodic current density, Al(III) could be incorporated in a deposit mainly composed of brucite, but only in small amount.

Luis García Rodríguez, Laura Castro-Santos, María Isabel Lamas Galdo

The electrical installation of a ship includes the generation, transport and distribution of the generated electrical energy to the electrical consumers on board. In recent years, there have been many attempts to replace traditional auxiliary generators with renewable energy sources, in particular solar panels, as this is a highly developed technology on land. Accordingly, this paper analyzes the different energy requirements on board a merchant vessel and carries out a feasibility analysis. The feasibility analysis considers technical, economic and legal aspects. Sustainable aspects are analyzed too, due to their importance nowadays. It is verified that the use of solar panels is only technically feasible for a small part of the ship’s total consumption, as the area required by the panels to cover the total demand would exceed the available area of the ship. Therefore, the possibility of installing solar panels for the fire detection system only was analyzed. This is a technically and legally feasible solution, but not an economically viable one. However, from a sustainability point of view, which takes into account economic, social and environmental aspects, this proposal is appropriate. This study concludes that, while solar panels are not a viable solution for covering all energy needs on merchant ships, they can be used for specific systems such as the fire detection network or similar small consumers, albeit with economic limitations. These findings provide valuable insights for future research and practical implementations of renewable energy solutions in the maritime sector.

Qingmiao Ma, Weige Liang, Haoming Chen et al.

Subsea pipelines are extensively utilized in transportation systems. Conducting regular and effective internal inspections of these pipelines to promptly identify internal defects and potential risks is of paramount importance to ensure safe operational practices. In response to the practical engineering requirements for the internal inspection of subsea pipelines, this paper presents the design of an inspection device capable of capturing point cloud data from pipelines with internal diameters of 100 mm and above and performing three-dimensional reconstruction through coding. This device clearly reveals internal pipeline defects and enables both qualitative and quantitative analyses. Upon designing the motion module, control system, and LiDAR-based detection module of the internal pipeline inspection device, the capacity to collect internal point cloud data and perform 3D reconstruction was achieved. An experimental prototype of the inspection device was manufactured and tested using a simulated pipeline constructed to replicate real-world conditions. An analysis of the inspection results demonstrates that the device can travel steadily inside the pipeline, and the collected point cloud data can be used for 3D reconstruction via coding, accurately and clearly displaying the internal 3D structure of the pipeline and its defects. This device provides a basis for the prediction of pipelines’ service lives.

Rodrigo Costa Batista, Elizaldo Domingues dos Santos, Luiz Alberto Oliveira Rocha et al.

The utilization of ocean wave energy through environmentally sustainable technologies plays a pivotal role in the transition toward renewable energy sources. Among such technologies, the Submerged Horizontal Plate (SHP) stands out as a viable option for clean power production. This study focuses on the system’s application in a region on the southern coast of Brazil, identified as a potential site for future installation. To investigate this system, a three-dimensional numerical wave tank was developed to simulate wave behavior and hydrodynamic loads using the Navier–Stokes framework in the computational fluid dynamics software ANSYS FLUENT 2022 R2. The volume of fluid approach was adopted to track the free surface. The setup for wave generation in the numerical wave tank was verified against analytical solutions to ensure precision and validated under the SHP’s non-oscillating condition. To represent the oscillating condition, boundary conditions constrained motion along the <i>x</i>- and <i>y</i>-axes, allowing movement exclusively along the <i>z</i>-axis. A parametric analysis of 54 cases, with varying geometric configurations, wave characteristics, and submersion depths, indicated that the oscillating SHP configuration elongated perpendicular to wave propagation, combined with specific wave conditions, achieved a theoretical mean efficiency of 76.61%.

Ian Thompson, Radu Chiritoiu, Teresa Magoga et al.

Fengming Du, Yuhong Zhang, Zetian Mi et al.

Under high sea conditions, liquefied natural gas (LNG) ships undergo significant shaking, which can affect the deformation and stress levels in the membrane tank walls. In this work, the structural characteristics of the corrugated steel inner wall in LNG ship membrane tanks were examined, different finite element models were established, and the structural characteristics under normal conditions, high sea conditions, and defective conditions were evaluated. The results revealed that corrugated steel exhibited high stress and strain under high sea conditions, with early signs of initial yield. In the presence of defects, the corrugated steel strip experienced higher stress and strain under the same load. Particularly, at a pressure of 10 bar, the defective corrugated steel exhibited a 2.3% increase in maximum stress than the defect-free corrugated steel. Additionally, the incorporation of reinforcement into the corrugated plate significantly reduced its stress and strain. Under a pressure of 10 bar, the reinforced corrugated plate exhibited a maximum stress of 503 MPa, which was 5.1% lower than that of the non-reinforced corrugated plate. This study provides theoretical support and guidance for designing and optimizing the inner wall structure of LNG ship membrane tanks.

Yang Liu, Qiang Zhang, Longjin Wang et al.

This paper investigates the problem of real-time parameter identification for ship maneuvering parameters and wave peak frequency in an ocean environment. Based on the idea of Euler discretion, a combined model of ship maneuvering and wave peak frequency (ship–wave) is made a discretion, and a discrete-time auto-regressive moving-average model with exogenous input (ARMAX) is derived for parameter identification. Based on the ideas of stochastic gradient identification and multi-innovation theory, a multi-innovation stochastic gradient (MI-SG) algorithm is derived for parameter identification of the ship–wave discretion model. Maximum likelihood theory is introduced to propose a maximum likelihood-based multi-innovation stochastic gradient (ML-MI-SG) algorithm. Compared to the MI-SG algorithm, the ML-MI-SG algorithm shows improvements in both parameter identification accuracy and identification convergence speed. Simulation results verify the effectiveness of the proposed algorithm.

Hyun-Sung Yang, Areumi Park, Heung-Sik Park et al.

The top shell, <i>Turbo sazae</i>, occurs commonly in the shallow rocky subtidal area of Jeju Island off the south coast of Korea, and it is one of the most valuable gastropod resources supporting the local shellfish industry. <i>T. sazae</i> landings in Jeju have declined dramatically in recent years, although the factors involved in this decline are yet to be identified. Recent studies also have reported that <i>T. sazae</i> is expanding its distribution range to the east coast of Korea, possibly due to the increasing seawater temperature. In this study, we investigated the hemocyte responses of <i>T. sazae</i> to elevated seawater temperatures in order to gain a better understanding of its immunological response to higher water temperatures. In this experiment, we exposed top shells to a gradual increase in seawater temperature, ranging from 22 °C to 30 °C, over a span of 9 days. We employed flow cytometry to assess various cellular immune responses, including hemocyte viability, phagocytosis capacity, and the production of reactive oxygen species (ROS) in <i>T. sazae</i>. The results showed that top shells exposed to elevated seawater temperature exhibited a significant decrease in phagocytosis capacity and an increase in ROS production after 3 days of the experiment. These findings indicate that an elevated seawater temperature imposes a stressful condition on <i>T. sazae</i>, characterized by reduced phagocytosis capacity and increased oxidative stress.

Floor P. Bakker, Solange van der Werff, Fedor Baart et al.

Reducing waiting times is crucial for ports to be efficient and competitive. Important causes of waiting times are cascading interactions between realistic hydrodynamics, accessibility policies, vessel-priority rules, and detailed berth availability. The main challenges are determining the cause of waiting and finding rational solutions to reduce waiting time. In this study, we focus on the role of the design depth of a channel on the waiting times. We quantify the performance of channel depth for a representative fleet rather than the common approach of a single normative design vessel. The study relies on a mesoscale agent-based discrete-event model that can take processed Automatic Identification System and hydrodynamic data as its main input. The presented method’s validity is assessed by hindcasting one year of observed anchorage area laytimes for a liquid bulk terminal in the Port of Rotterdam. The hindcast demonstrates that the method predicts the causes of 73.4% of the non-excessive laytimes of vessels, thereby correctly modelling 60.7% of the vessels-of-call. Following a recent deepening of the access channel, cascading waiting times due to tidal restrictions were found to be limited. Nonetheless, the importance of our approach is demonstrated by testing alternative maintained bed level designs, revealing the method’s potential to support rational decision-making in coastal zones.

Howard Theunissen, Theo Van Niekerk, Jan Harm Pretorius

The maritime industry is inherently global, with seafarers and expatriate skilled engineering graduates employed worldwide, away from the places they grew up and obtained their specialist qualifications.  Consequently, any higher education qualification in the maritime sector must ensure that graduates are equipped to compete internationally for employment opportunities, and be prepared for the engineering challenges of the future.This paper presents a study on the naval architecture and marine engineering (NAME) higher education in South Africa and compares it to three international marine education universities.  A qualitative content analysis methodology was employed to analyse the module content of each international institution.  Patterns that emerged from the analysis were used to compare against the curriculum of the current Bachelor of Engineering Technology in Marine Engineering degree programme that is offered by the Nelson Mandela University in South Africa (since 2018).The analysis of the international programmes identified 18 themes that a quality NAME programme should encompass to meet the academic requirements for the future engineers in the global maritime sector.  The study recommends the addition of a 4th year honours degree and a 5thyear taught master’s degree to the existing three-year undergraduate Bachelor degree in Engineering Technology in Marine Engineering.  The proposed curriculum, unique in the South African Higher Education environment, will enable graduates to apply mathematical and scientific principles to the ‘design, development and operational evaluation of self-propelled, stationary or towed vessels operating on or under the water, including inland, coastal and ocean environments’

Feng Zhang, Hao Tang, Nyatchouba Nsangue Bruno Thierry et al.

Codends are the posterior components of trawl nets that collect the catch and play a crucial role in the selectivity process. Due to the accumulation of catch and the variety of catch types, the quality of catch and trawl selectivity can be negatively impacted. Therefore, this study aims to investigate the effects of various catch configurations on the hydrodynamic characteristics, geometrical profile, and fluttering motions of the codend in a flume tank. A codend structure was designed and tested using various catch configurations, including grooved-type configurations (canvas, green canvas, basketballs) and spherical configurations (table tennis balls filled with water, balloons filled with water, and balls made of twine) in the flume tank. The sea trial data were compared with the flume tank data. The results indicate that there were no significant differences in the codend profiles between the different catch configurations. The drag of the codend with a grooved-type configuration was 13.63% greater than that obtained using a spherical configuration as the catch. The wavelet coefficient obtained from the codend drag revealed that the oscillations of the codend with a grooved-type catch configuration began at a periodicity of 0.07 s and were more intense than that of the codend with the spherical catch configuration. Moreover, these amplitudes increased as the codend flow velocity increased. The wavelet analysis results showed that the dominant frequency of the periodic high-energy coherent structures for the codend drag and codend displacements was detected at a low-frequency. In terms of displacement oscillation characteristics, the table tennis ball filled with water was an approximate substitute for real catch during the sea trial because the difference in wavelet coefficients for the codend displacements in amplitude and the period between the model codend with the table tennis ball filled with water and the full-scale codend was 91% and 89%, respectively. The findings of this study confirm the feasibility of replacing real catch with simulated catch configurations with similar shapes in model testing. They can provide basic scientific data for improving the hydrodynamic characteristics and selectivity of the codend structure.

Daniele Trogu, Simone Simeone, Andrea Ruju et al.

This paper investigates the dynamics of the cross-shore extensions of banquettes, a sedimentary structure mostly made by rests of <i>Posidonia oceanica</i> (L.) Delile, in a sandy urban beach located in the Gulf of Cagliari, Italy, western Mediterranean. A video monitoring station was installed above the promontory south of the beach. We analysed a four-year image database and related these dynamics to wave and wind parameters (obtained from the Copernicus and ERA5 databases) from September 2016 to September 2020. Our results showed that banquette deposition occurred in concomitance with the presence of leaf litter in the surf zone associated with mild storm events. Erosion of the banquettes occurred during more intense storms. When leaf litter was not present in the surf zone, banquettes were not deposited even with mild storms. Wind can influence the banquette dynamics: under certain conditions of speed intensity, the banquettes may be removed offshore, supplying litter in the surf zone, or they may be covered by sediment. The permanence of the banquettes on the beaches also depended on their composition: when the banquettes were intertwined with reeds, their removal by the waves did not occur even during intense storms, and this sedimentary structure can protect the beach from flooding.

Di Wang, Linlong Yang, Wei Li et al.

The combination of multi-phase extension and pre-existing fault reactivation results in a complex fault pattern within hydrocarbon-bearing basins, affecting hydrocarbon exploration at different stages. We used high-resolution 3D seismic data and well data to reveal the impact of multi-phase extension and pre-existing fault reactivation on Cenozoic fault pattern changes over time in the Jiyang Depression of eastern China. The results show that during the Paleocene, a portion of NW-striking pre-existing faults reactivated under NS extension and controlled the basin structure (type 1). Other parts of the NW-striking pre-existing faults stopped activity and served as weak surfaces, and a series of NNE-striking faults were distributed in an en-echelon pattern along the NW direction at shallow depths (type 2). In areas unaffected by pre-existing faults, NE-striking faults formed perpendicular to regional stresses. During the Eocene, the regional stresses shifted clockwise to near-NS extension, and many EW-striking faults developed within the basin. The NE-striking faults and the EW-striking faults were hard-linked, forming the ENE-striking curved faults that controlled the structure in the basin (type 3). The NNE-striking faults were distinctly strike-slip at this time, with the ENE-striking faults forming a horsetail pattern at their tails. Many ENE-striking faults perpendicular to the extension direction were formed in areas where the basement was more stable and pre-existing faults were not developed (type 4). There were also developing NS-striking faults that were small in scale and appeared in positions overlapping different main faults (type 5). Additionally, different fault patterns can guide different phases of hydrocarbon exploration. Type 1, type 2, and type 3 faults are particularly suitable for early-stage exploration. In contrast, type 4 and type 5 faults are more appropriate for mature exploration areas, where they may reveal smaller hydrocarbon reservoirs.

Helong Shen, Huang Tang, Yong Yin

Yue QIN, Guan-lin WANG, Sheng GUAN et al.

Marine mesoscale processes, including vortices, fronts, and internal waves, are a class of important dynamic processes in the ocean that have a significant influence on global climate change and the transport of marine energy, heat, and materials. The observation and investigation of such processes also have important practical significance in the field of marine resources, organism exploration, and military domains. Underwater gliders have recently become important devices for observing mesoscale processes. “Petrel-Ⅱ,” a type of autonomous underwater glider, is considered the main focus of this study. First, a dynamics model is established based on the momentum and angular momentum theorems. Simulink is then used to confirm the feasibility of the proposed model. According to the simulation results, the proposed dynamic model can realize motion simulation well. Finally, based on the different requirements for the detection of several mesoscale processes, different sampling motion schemes are presented, and a motion simulation of spatial sampling is provided. This study could provide a reference and optimization parameters for future practical observations and applications.

Marta Umbert, Nina Hoareau, Jordi Salat et al.

The Vendée Globe is the world’s most famous solo, non-stop, unassisted sailing race. The Institute of Marine Sciences and the Barcelona Ocean Sailing Foundation installed a MicroCAT on the One Ocean One Planet boat. The skipper, Dídac Costa, completed the round trip in 97 days, from 8 November 2020 to 13 February 2021, providing one measurement of temperature and conductivity every 30 s during navigation. More than half of the ship’s route was in the sub-Antarctic zone, between the tropical and polar fronts, and it passed through areas of oceanographic interest such as Southern Patagonia (affected by glacier melting), the Brazil–Malvinas confluence, the Southern Pacific Ocean, and the entire Southern Indian Ocean. This sailing race gave a rare opportunity to measure in-situ sea surface salinity in a region where satellite salinity measurements are not reliable. Due to the decreased sensitivity of brightness temperature to salinity in cold seas, retrieving sea surface salinity at high latitudes remains a major challenge. This paper describes how the data are processed and uses the data to validate satellite salinity products in the sub-Antarctic zone. The sailing race measurements represent surface information (60 cm depth) not available from drifters or Argo floats. Acquiring measurements using round-the-world sailing races would allow us to analyse the evolution of ocean salinity and the impact of changes in the ice extent around Antarctica.

Guigui Wang, Shihan Tan, Ge Song et al.

The CBATS (carrier-based aircraft take-off and landing training system) is an important application of virtual reality technology in the simulation field. Large-scale, real-time ocean simulations are the biggest challenge to the authenticity of the visual system of CBATS and are also currently the main research hotspot in the field of computer graphics. In this paper, a hybrid Ocean Modeling Method based on wavelet transform is presented. This method introduces an accurate phase calculation and a wind-field model solution to compensate for the randomness of wave generation and the lack of physical mechanism in spectral methods. The computational cost is greatly reduced by using a rough spatial grid to calculate the amplitude and phase values at any point in space, which effectively avoids Nyquist–Shannon Theorem limitations caused by the numerical solutions of PDEs (partial differential equations), and a high-fidelity simulation of high frequency, detailed sea surface and coherent phase-dependent wave effects is achieved. Practical verification shows that the method can fully meet the real-time simulation training requirements of CBATS with a strong real-time performance and good stability. Thus, it could play a significant role in improving the performance of the visual system.

Joel R. Perez, Carlos A. Reusser

Nowadays, marine propulsion systems based on thermal machines that operate under the diesel cycle have positioned themselves as one of the main options for this type of applications. The main comparative advantages of diesel engines, compared to other propulsion systems based on thermal cycle engines, are the low specific fuel consumption of residual fuels, and their higher thermal efficiency. However, its main disadvantage lies in the emissions produced by the combustion of the residual fuels, such as carbon dioxide (CO₂), sulfur oxide (SO_x), and nitrogen oxide (NO_x). These emissions are directly related to the operating conditions of the propulsion system. Over the last decade, the International Maritime Organization (IMO) has adopted a series of regulations to reduce CO₂ emissions based on the introduction of an Energy Efficiency Design Index (EEDI) and an Energy Efficiency Operational Indicator (EEOI). In this context, adding a Shaft Generator (SG) to the propulsion system favoring lower EEDI and EEOI values. The present work proposes a selective control system and optimization scheme that allows operating the shaft generator in Power Take Off (PTO) or Power Take In (PTI) mode, ensuring that the main engine operates, always, at the optimum fuel efficiency point, thus ensuring minimum CO₂ emissions.

João Pedro T. P. de Queiroz, Marcelo L. Cunha, Ana Pavlovic et al.

This work searched for the optimal geometrical configuration of simply supported stiffened plates subjected to a transverse and uniformly distributed load. From a non-stiffened reference plate, different geometrical configurations of stiffened plates, with the same volume as the reference plate, were defined through the constructal design method. Thus, applying the exhaustive search technique and using the ANSYS software, the mechanical behaviors of all the suggested stiffened plates were compared to each other to find the geometrical configuration that provided the minimum deflection in the plate&rsquo;s center when subjected to this loading. The optimum geometrical configuration of stiffeners is presented at the end of this work, allowing a reduction of 98.57% for the central deflection of the stiffened plate if compared to the reference plate. Furthermore, power equations were adjusted to describe the deflections for each combination of longitudinal and transverse stiffeners as a function of the ratio between the height and the thickness of the stiffeners. Finally, a unique equation for determining the central deflections of the studied stiffened plates based only on the number of longitudinal stiffeners without significantly losing accuracy has been proposed.

Juan L. Garzon, Celso M. Ferreira

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