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Showing papers in "Ships and Offshore Structures in 2022"


Journal ArticleDOI
TL;DR: In this paper , a diffuser-augmented DATT was determined and regarded as efficient in converting tidal energy, which indicates that the diffuser can effectively reduce the loss of blade tip.
Abstract: ABSTRACT Diffuser-augmented tidal turbines (DATTs) are determined and regarded as efficient in converting tidal energy. In this paper, which is stipulated by a large group of researchers, the highly established module performance of a diffuser turbine is numerically studied by the Computational Fluid Dynamics (CFD). Numerical analysis shows that the pressure distributions near the blade tip gradually change for a DATT than a non-diffuser augmented tidal turbine (NDATT), which indicates that the diffuser can effectively reduce the loss of blade tip. The practical assessment through anticipated and assured procedure in the application of this turbine was conducted offshore at Daishan Island and observed to have slightly higher energy efficiency than the experimental model.

26 citations


Journal ArticleDOI
TL;DR: In this article , the fluid-structure interaction (FSI) from wave diffraction forces on CALM buoys and cylindrical structures, based on the hydrodynamics with connections, was investigated.
Abstract: ABSTRACT This research fills the gap in understanding fluid–structure interaction (FSI) from wave diffraction forces on CALM buoys and cylindrical structures, based on the hydrodynamics with connections. Recently, there is an increased application of (un)loading marine hoses for Catenary Anchor Leg Moorings (CALM) buoy systems in the offshore industry due to the need for more flexible marine structures that are cost-saving, easier to install, and service. However, different operational issues challenge these hoses, like during hose disconnection. Also, the fluid behaviour was investigated based on the analytical and numerical models. The numerical modelling involves the boundary element method (BEM) and Orcaflex line theory. Hydrodynamic analysis is conducted on the disconnection-induced load response of marine bonded hoses during normal operation and accidental operation under irregular waves. A comparative study on hose performance during normal operation and accidental operation is also presented. Results of statistical analysis on CALM buoy system shows good motion characteristics.

20 citations


Peer ReviewDOI
TL;DR: In this paper , the authors present a review of the history and development of marine hoses and their configurations in the offshore industry, highlighting the evolutions in the hose designs, potentials of the hoses, and recent state-of-the-art developments in the industry.
Abstract: ABSTRACT Marine bonded hoses are conduit-tubular structures used for loading, discharging, transferring and transporting fluid products like oil, gas, and water. These marine conduits are applied in the offshore industry by utilising novel marine materials and sustainable technologies. Based on sustainability, there are advances made as solutions for challenging environments. These challenges include scouring gases, deep water regions, changing sea water temperatures, platform loads and vessel motions. These environments also require sustainable materials like marine composites. This paper reviews historical timeline and patent development of hoses in the marine environment. It highlights key developments on marine hoses and their configurations. These configurations include FPSO-FSO with hose attachments in catenary configurations and CALM buoy-PLEM in Lazy-S configurations. The review also discusses the evolutions in the hose designs, potentials of the hoses, and recent state-of-the-art developments in the industry. Comprehensive discussions with necessary recommendations are made for fluid applications in the offshore industry.

15 citations


Journal ArticleDOI
TL;DR: In this article , an improved artificial fish swarm algorithm (IAFSA) is proposed to improve the efficiency and path quality of autonomous surface vessels (ASVs) by using a directional operator and a probability weight factor to adjust the frequency of executing random behavior.
Abstract: ABSTRACT Path planning is one of the key technologies in the research of autonomous surface vessels (ASVs). In this paper, an improved artificial fish swarm algorithm (IAFSA) is proposed. The algorithm is modified from four perspectives: (1) A directional operator is introduced to improve the efficiency. (2) To avoid local optimum, a probability weight factor is proposed to adjust the frequency of executing random behaviour. (3) An adaptive operator has been applied aims at better convergence performance. (4) The waypoint modifying path smoother is used to improve the path quality. A comparative study has been carried out between IAFSA and the other state-of-the-art algorithms, and the results indicate that the proposed algorithm outperforms the others in both efficiency and path quality. Finally, IAFSA is integrated into the GNC system in a model ship. A computer-based sea trial around the Nan Hai area has been conducted, and environmental disturbances including wind, waves, and currents are considered. The results have shown that IAFSA is suitable for practical application.

13 citations


Journal ArticleDOI
TL;DR: In this paper , a B-spline-based path smoother is applied to the algorithm to enhance its feasibility in cooperating with the ASV controller and simulation results have demonstrated that the proposed method is more efficient than the other state-of-the-art algorithms.
Abstract: Featuring agile controllability, high-level autonomy, and powerful field operational advantages, autonomous surface vessels (ASVs) are gaining increasing attention worldwide. Central to the control of ASVs, path planning is one of the key technologies that ensure the navigation safety. However, many of the previous works to solve the path planning problem are to find a collision-free and shortest path, but the solutions are not satisfied by the safety requirements and the non-holonomic constraints of ASVs. This paper expands on our previous work on the improved artificial fish algorithm (IAFSA) to address these challenges. The expanding technique is introduced to modify the grid cost, and a B-spline-based path smoother is applied to the algorithm to enhance its feasibility in cooperating with the ASV controller. Simulation experiments have been conducted to illustrate the effectiveness of the proposed method. Moreover, the new algorithm is tested in the USV control system model in a practical environment. The simulation results have demonstrated that the proposed method is more efficient than the other state-of-the-art algorithms, and the simulation with the ASV model illustrated its excellent performance cooperating with the control system. Therefore, the proposed method can be considered as a reliable algorithm to solve the path planning problem of ASVs.

8 citations


Journal ArticleDOI
TL;DR: In this paper , an ANN-based formula was proposed to predict the ultimate strength of perforated steel plates and its accuracy was compared with the formulations presented in previous studies and the proposed formula provided high accuracy and can be used as a reliable formula in practice.
Abstract: ABSTRACT In the current paper, using finite element models (FEM), an extensive numerical study is performed on the behaviour of the steel plates with a circular hole in their centre subjected to compressive axial loading. For this purpose, 270 perforated steel plates were modelled and analysed using ABAQUS software. The effects of four main variables including plate length, hole diameter, plate thickness, and yield stress were discussed. Then, using the database provided by FEM, the artificial neural network (ANN) method was used to develop a predictive model to estimate the ultimate strength of steel plates with a circular hole in the centre. Finally, an ANN-based formula was proposed to predict the ultimate strength of perforated steel plates and its accuracy was compared with the formulations presented in previous studies. Based on the results, the proposed formula provided high accuracy and can be used as a reliable formula in practice.

8 citations


Journal ArticleDOI
TL;DR: In this article , a partitioned two-way coupled CFD-FEA fluid-structure interaction (FSI) method is used to study the water entry of flat plates with different impact velocities and wedges with different deadrise angles.
Abstract: In rough seas, ships may be subject to wave-induced slamming loads. Thus, modelling of fluid and structural mechanics, and their dynamic interactions can help with the evaluation of fluid actions and the prediction of wave-induced loads for use in ship design. In this paper a partitioned two-way coupled CFD-FEA fluid–structure interaction (FSI) method is used to study the water entry of flat plates with different impact velocities and wedges with different deadrise angles. Results show that when flexible plate dynamics prevail, at relatively low to medium impact velocity a negative correlation between the nondimensional pressure and water entry velocities is evident near plate centre areas. A steady correlation exists when only stiff plate dynamics prevail. Pressure differences between stiff and flexible wedges become evident at small deadrise angles. The similarity of the pressure distribution during water impingement of ideally stiff wedge structures is not valid when structural flexibility prevails.

7 citations


Journal ArticleDOI
TL;DR: In this paper , a simulation of a 50000 DWT ship's hybrid electrical generation system is presented, where the optimal number of batteries, charging, and discharging times are determined based on multi-attribute decision-making methods.
Abstract: ABSTRACT This study aims to ensure an extensive assessment of the 50000 DWT tanker vessel's hybrid electrical generation system. A numerical model was constructed using the data obtained from the ship. The simulation comprised load distributions of diesel generators in various operation modes. Multi-attribute decision-making methods determined the optimal number of batteries, charging, and discharging times, then, the simulation computed fuel consumption and emissions of the hybrid plant using two charging strategies. The first scenario involved using generators, while the second used a waste heat recovery system. The results indicated that the first strategy has the potential of fuel-saving up to 8.618% and is suitable for ships that spend more time in the port. The second strategy can save up to 18.145% fuel and is usable for all operation modes. The predictions of future fuel savings depicted that the proposed system could save up to 2109.408 t fuel in five years.

7 citations


Journal ArticleDOI
TL;DR: In this article , the authors compared diesel and renewable hydrogen-powered ships using Life Cycle Assessment (LCA) and Life Cycle Cost Assessment (LCCA) as a case study, three different ships sailing in the Red Sea area are investigated.
Abstract: ABSTRACT The International Maritime Organization proposes several strategies to eliminate the adverse effects of ship emissions. The most important is finding alternative fuels, such as hydrogen. The current paper aims to compare diesel and renewable hydrogen-powered ships using Life Cycle Assessment (LCA) and Life Cycle Cost Assessment (LCCA). As a case study, three different ships sailing in the Red Sea area are investigated. The environmental outcomes are presented in terms of global warming potential (GWP), photochemical potential, eutrophication potential, particulate matter and acidification potential. Producing hydrogen fuel onboard ships will increase the total carbon footprint by 10%–28% higher than the currently used diesel fuels. Economically, the cost-effective target will be achieved at the cost of hydrogen production by electrolysis below 5.15$/kg.

7 citations


Journal ArticleDOI
TL;DR: In this paper , a review of analytical, numerical, and experimental methods for evaluating the structural response of Offshore Wind Turbines (OWT's) during ship collision events is presented.
Abstract: ABSTRACT This paper presents a literature review of analytical, numerical, and experimental methods for evaluating the structural response of Offshore Wind Turbines (OWT's) during ship collision events. The different energy transfer mechanisms involved throughout a collision against fixed or floating OWT substructures are examined, whilst documenting some of the most common procedures in the assessment of wind load effects, soil–structure interaction, mooring lines contribution and hydrodynamic coupling. A survey of internal mechanics and external dynamics approaches developed for ship-structures collision events is carried out with a discussion on their potential application in analyses involving different types of substructures. Moreover, different hydrodynamic coupling schemes found in the literature are studied, highlighting the importance of hydro-effects in the collision analysis. Common practices in the use of metallic and cementitious material constitutive models in ship-collision analysis are also presented, whereas the structural behaviour of reinforced concrete structures submitted to impact loads, which has been rarely studied outside high-velocity impact/blast applications, is discussed in the current context. Finally, some of the most important limitations of the analytical and numerical models used in ship-OWT collisions are identified, from which suggestions are provided for future research endeavors.

7 citations


Journal ArticleDOI
TL;DR: In this paper , the numerical accuracy of time dependent potential and source methods is compared against analytical and other numerical results using an in-house transient wave-body interaction three-dimensional wave Green function computational tool of ITU-WAVE.
Abstract: ABSTRACT The numerical accuracy of time dependent potential and source methods is compared against analytical and other numerical results using an in-house transient wave-body interaction three-dimensional wave Green function computational tool of ITU-WAVE. The time dependent Impulse Response Functions (IRFs) are used to predict the behaviour of radiation forces, exciting forces, and response of floating bodies. For radiation force IRFs, the numerical results show that potential method converges with less numbers of panels compared to source method, while in the case of diffraction force IRFs, the convergence is achieved with the same number of elements for both potential and source methods. As potential method achieves convergence faster than source method for radiation force IRFs prediction, potential method is applied for the hydrodynamic and response parameters of a twin-hull high-speed craft. The present ITU-WAVE numerical results, which are compared with experimental, analytical, and other numerical results for validation purposes show satisfactory agreements.

Journal ArticleDOI
TL;DR: In this article , a case study of a marine Main Engine is used to examine faults in the engine's Air Cooler and Air and Gas Handling System, and it is concluded that any simultaneous abnormal deviations in the Main Engine's Exhaust Gas Temperature are more likely to be caused by a fault in the Air and gas Handling System.
Abstract: ABSTRACT Marine maintenance can improve ship performance by leveraging predictive maintenance, Machine Learning and Data Analytics. This paper aims to enrich the literature, by developing a novel framework for ship diagnostics based on operational data and the probability of faults. Moreover, the framework can identify the root cause of developing faults avoiding black-box Neural Networks, and complex physics-based models. This research integrates Machine Learning-based Fault Detection, Exponentially Weighted Moving Average control charts, and Bayesian diagnostic networks which allow the examination of the rate of development (fault profile) of faults and failure modes. For validation, the case study of a marine Main Engine is used to examine faults in the engine’s Air Cooler and Air and Gas Handling System. It is concluded that any simultaneous abnormal deviations in the Main Engine’s Exhaust Gas Temperature are more likely to be caused by a fault in the Air and Gas Handling System.

Journal ArticleDOI
TL;DR: In this article , the position of the pivot point relative to the center of rotation is calculated, and the dependence of the rotation center displacement on the longitudinal speed of the vessel has been obtained.
Abstract: ABSTRACT The article deals with the use of Pivot Point to optimize vessel control. It is shown that the position of the Pivot Point should be calculated relative to the center of rotation, and not the center of gravity, as previously thought. For the first time, the dependence of the rotation center displacement on the longitudinal speed of the vessel has been obtained. For the linear model of the vessel, the subdomains of admissible controls are constructed, and the special positions of the Pivot Point are analyzed. The dependence of the control distribution coefficient on the position of the Pivot Point is obtained. Optimal controls are considered. The operability and efficiency of the methods have been verified by mathematical modeling.

Journal ArticleDOI
TL;DR: In this article , a polyhedral preform with a uniform thickness of 1.1mm was inscribed on the circular section of a target toroid with a rotation radius of 150mm and a cross-sectional radius of 75mm.
Abstract: ABSTRACT The hydroforming and buckling of toroids with polyhedral sections were examined. The cross section of a polyhedral preform had the form of an irregular octagon with a uniform thickness of 1.1 mm. This octagon was inscribed on the circular section of a target toroid with a rotation radius of 150 mm and a cross-sectional radius of 75 mm. Two nominally identical preforms were fabricated, internally hydroformed, and externally collapsed. The internally and externally applied pressures were recorded, and the geometric shapes and thicknesses were measured before and after the hydroforming process. The nonlinear finite-element method was used to investigate the hydroforming and buckling properties. The experimental results and numerical estimations were compared, and the results indicate that the hydroformed toroid can be employed in underwater vehicles. Jordan’s equation can provide a conservative prediction of the ultimate allowable outer pressure of hydroformed toroids when the hydroforming pressure exceeds a certain threshold.

Peer ReviewDOI
TL;DR: In this paper , a brief review of the mechanism and various phenomena that play a crucial role in the performance of a marine propeller from a different aspect is presented, where different structural analyses, suitable material selection, various propulsive methods, acoustic and vibration analysis are discussed in detail.
Abstract: ABSTRACT Propeller is the main energy-producing device for any marine vehicle. To make waterway communication economical, efficient and environment friendly, improvement of ship propulsion system is achieving great interest nowadays. This paper aims to perform a brief review of the mechanism and various phenomena that play a crucial role in the performance of marine propeller from a different aspect. Here different structural analyses, suitable material selection, various propulsive methods, acoustic and vibration analysis are discussed in detail. Alongside, various energy-saving devices (ESDs) are presented in brief to understand the recovery of energy losses due to cavitation and other associated factors. Various optimization techniques and control mechanism are also highlighted here in brief. The main objective of the paper is to present the current research scenarios in the field of marine propeller and identify future research scope in the respective field.

Journal ArticleDOI
TL;DR: In this paper , an original Waste Heat Recovery (WHR) variable layout plant is described to produce steam from the exhaustgases of marine dual-fuel engines. But the layout of the proposed steam plant is conceived in a double configuration to satisfy both the stack temperature constraints of the engine exhaust gas, due to the use of diesel oil (no less than 160°C as outlet gas temperature) or natural gas (there are no particular stack temperature limits).
Abstract: ABSTRACT The paper describes an original Waste Heat Recovery (WHR) variable layout plant to produce steam from the exhaustgases of marine dual-fuel engines. A large part of the steam feeds an electric turbogenerator to improve the ship's energy efficiency.The layout of the proposed steam plant is conceived in a double configuration to satisfy both the stack temperature constraints of theengine exhaust gas, due to the use of diesel oil (no less than 160°C as outlet gas temperature) or natural gas (there are no particularstack temperature limits). The comparison with a traditional WHR single pressure steam plant shows the potential benefits of thevariable configuration. Indeed, the proposed solution allows a better exploitation of the potential thermal energy of the natural gas,without precluding a proper performance even in diesel mode, with a moderate weight increase compared to a single pressure WHR system.

Journal ArticleDOI
TL;DR: In this paper , the authors present a methodology as a framework that can be used to analyze the related consequences of ship-ship collision events using simulations and evaluations, including nonlinear finite element analyses of the collision event, a METOCEAN data analysis module, damage stability simulations, analyses of damaged ship's ultimate strength and structural integrity, oil spill drift simulations, and finally, an evaluation of the three abovementioned consequences.
Abstract: ABSTRACT A ship collision accident may pose a threat to human lives, the environment and material assets. A damaged ship can suffer from the loss of ship stability, reduced global structural strength, and the loss of the integrity of internal tanks carrying polluting liquids. This study presents a methodology as a framework that can be used to analyze the related consequences of ship-ship collision events using simulations and evaluations. The methodology includes nonlinear finite element analyses of the collision event, a METOCEAN data analysis module, damage stability simulations, analyses of the damaged ship’s ultimate strength and structural integrity, oil spill drift simulations, and finally, an evaluation of the three abovementioned consequences. A case study with a chemical tanker subjected to collision demonstrates the methodology. The collision event was assumed to occur in the Kattegat area (between Sweden and Denmark) at a ship route intersection with high ship traffic density.

Journal ArticleDOI
TL;DR: In this article , the buckling and postbuckling of nearly cylindrical shell (NCS) made of functionally graded porous material (FGPM) and subjected to external lateral pressure (ELP) in thermal environments is investigated.
Abstract: ABSTRACT This paper investigates the buckling and postbuckling of nearly cylindrical shell (NCS) made of functionally graded porous material (FGPM) and subjected to external lateral pressure (ELP) in thermal environments. The variation of two material constituents through the shell thickness is modelled by a power-law distribution. Porosities are assumed to distribute into FGPM according to forms of cosine functions. Basic equations in terms of deflection and stress function are established within the framework of classical shell theory taking into account von Kármán – Donnell nonlinearity. Boundary edges of the NCS are assumed to be simply supported and tangentially restrained. Multi-term analytical solutions are assumed and Galerkin method is used to derive expressions of buckling loads and nonlinear load–deflection relation. Parametric studies are carried out to assess the effects of coefficient and distribution type of porosity, thermal environments, geometry properties and in-plane boundary condition on the critical loads and postbuckling strength of pressure-loaded FGPM NCSs.

Journal ArticleDOI
TL;DR: In this paper , a comparative study of analytical approaches and codified rules are compared through screened experiment data that have realistic imperfections and different shape parameters in the range generally applied for marine structures.
Abstract: The ultimate strength of spherical shells under external pressure has been an attractive topic in the field of marine structures. However, recent studies have revealed that the current theoretical approaches are hardly compatible with the actual hulls, which indicates that the ultimate strength models still need to be reevaluated and unified. To address this challenge, a comparative study has been conducted in this paper. Various analytical approaches and codified rules are compared through screened experiment data that have realistic imperfections and different shape parameters in the range generally applied for marine structures. The model evaluation criteria have been established by implementing statistical model uncertainty factors in terms of bias and coefficient of variation. A comparison of the results has been made from three different aspects including shell shape, R/t and geometrical parameters to evaluate their performance. Based on the calculation outcome, analysis has been made to study the theory behind those models and determine their limitations and recommended application range.

Journal ArticleDOI
TL;DR: In this paper , a decision-making approach was developed based on the associated issues, processes and the best solution under current conditions for selecting the ballast water treatment system for ships.
Abstract: ABSTRACT Selection of the right ship ballast water treatment system is quite costly. In the present study, a decision-making approach was developed based on the associated issues, processes and the best solution under current conditions for selecting the ballast water treatment system for ships. The analysis of the study data revealed that the best decision-making system should include integrated DEMATEL (The Decision Making Trial and Evaluation Laboratory) and ANP (Analytic Network Process) methods, especially since the current criteria interacted, there was a network among the criteria sets, and the system approach should be holistic. The study findings demonstrated that C4 (impact on the technical status of the ship) was the most significant criterion, while C11 (initial investment cost) was the most significant sub-criterion.

Journal ArticleDOI
TL;DR: In this paper , a comprehensive study on spar with curved neck profile with a heave plate near the surface is made to assess the effect of geometry and location of heave plates on heave damping.
Abstract: A comprehensive study on spar with curved neck profile with a heave plate near the surface is made to assess the effect of geometry and location of heave plate on heave damping. A CFD-based approach is adopted to extract the damping and added mass by tracing the heave decay, and the results are validated with those from experiments. Free heave decay tests are conducted on scaled spar models (1:100 scale) in calm water and the results compare reasonably well with that obtained from the numerical model. The experiments conducted for heave motion response indicate a reduction in heave response at resonance. In addition, the effects of heave plate diameter ratio (1–2) and heave plate position to draft ratio (0–0.9) on the heave damping of buoy form spar have been studied numerically to identify the most favorable configuration in terms of heave damping.

Journal ArticleDOI
TL;DR: In this paper , the applicability of 2D numerical simulation between the response of a two-dimensional numerical simulation and the actual response of the vortex shedding was discussed, and independent calculations under different speed reduction conditions were employed to suit practical application scenarios.
Abstract: The VIV responses of the circular cylinder at low and moderate Reynolds numbers are calculated according to two-dimensional numerical simulation and the fourth-order Runge–Kutta algorithm. The first part of the study is focused on the applicability of 2D numerical simulation between the response of 2D numerical simulation and the actual response, which can guide the preliminary engineering studies by vortex shedding. The reasonable vortex shedding mode of each branch, and the change process of the trajectory from the ‘8’ type to the ‘droplet’ type, are discussed in the second part of the study. And independent calculations under different speed reduction conditions are employed to suit practical application scenarios. The comparison shows the applicability of the 2D numerical simulations at low Reynolds numbers. Although the amplitude calculation results at moderate Reynolds numbers are inconsistent with the experimental results, the two-dimensional numerical simulation has good reliability in the trailing vortex capture.

Journal ArticleDOI
TL;DR: In this article , the influence of perforated chamfer on the hydrodynamic performance of the heave plate was studied through physical experiments and numerical simulations, and the results of the numerical simulations and physical experiments revealed that hydrodynamics changed consistently.
Abstract: ABSTRACT In this study, the heave plate of a DeepCwind floating wind turbine platform with a capacity of 5 MW was used as the research object. The influence of the perforated chamfer on the hydrodynamic performance of the heave plate was studied through physical experiments and numerical simulations. Vertical force amplitudes, additional mass coefficients, and damping coefficients were obtained for heave plates with different types of perforations. The results of the numerical simulations and physical experiments revealed that hydrodynamic coefficients changed consistently. During the same period, the damping and additional mass coefficients of the heave plate gradually decreased and increased with an increase in the motion amplitude, respectively. When comparing with different perforation angles, the coefficients initially decrease and then increase with an increase in the perforation angle. In the case of a large perforation angle, the coefficients were higher than those of the conventional heave plate without perforations.

Journal ArticleDOI
TL;DR: In this paper , the interaction between oblique waves and a surface-piercing floating porous box located near to an impermeable sea wall is studied under the hypothesis of linearised water wave theory.
Abstract: ABSTRACT The interaction between oblique waves and a surface-piercing floating porous box located near to an impermeable sea wall is studied under the hypothesis of linearised water wave theory. The solution for the associated boundary value problem is developed using combined eigenfunction expansion and multi-domain boundary element methods. The reflection coefficients, surface elevation and hydrodynamic loads on the system are computed to examine the effect of different waves and structural parameters. The study reveals that waves reflected by the structure and wall decrease for increasing the porosity of the structure. The normalised spacing from permeable box to the sea wall plays a major role in the attenuation of wave load on the impermeable sea wall. Furthermore, the wave reflection follows a periodically oscillatory trend as the spacing from the box to the wall increases. The study concluded that on the inshore side, a serene environment can be formed in the presence of the floating permeable box.

Journal ArticleDOI
TL;DR: In this paper , a numerical study on the application of VSR in a fillet welded T-joint made of low carbon steel is presented, where the results demonstrate significant reduction of residual stress due to the vibration.
Abstract: ABSTRACT Residual stress generated during welding is a prominent factor for estimating the fatigue life and load-bearing capacity. Vibratory Stress Relief (VSR) is a promising technique to reduce the residual stress on welded components. However, depending on the orientation and size of the plate(s), practical implementation of VSR may require large amount of energy for vibrating the welded plate(s), which limits its effectiveness and application. This article presents a numerical study on the application of VSR in a fillet welded T-joint made of low carbon steel. Finite element simulation is carried out by adopting a sequentially coupled thermal and mechanical analysis approach. The numerical set-up has been validated. The results demonstrate significant reduction of residual stress due to the vibration. It has been observed that vibrating the stiffener is more effective than vibrating the base plate with the same force – which could be beneficial for the fabrication of stiffened panels.

Journal ArticleDOI
TL;DR: In this article , the compressive resistance of pillars used in ship structures is studied under a reliability perspective by examining sample cases and postulating over the practical scantling range of interest.
Abstract: ABSTRACT The compressive resistance of pillars used in ship structures is studied under a reliability perspective. A particular focus is placed on the study of Square Hollow Section (SHS) welded profiles by examining sample cases and postulating over the practical scantling range of interest. Uncertainty in the material and production imperfections have been probabilistically modelled by considering representative statistical structures. A pre-defined number of non-linear finite element simulations has been performed based on DOE sampling schemes in accordance with the response surface methodology. The generated surrogates were used within a Monte Carlo Simulation (MCS) framework for uncertainty propagation. The obtained statistical structures allowed for the generalised reliability assessment of SHS pillars which further allows for the subsequent proposal of deterministic utilisation factors for practical design.

Journal ArticleDOI
TL;DR: Wang et al. as mentioned in this paper proposed a new model named STD-Yolov5 to increase the model speed, accuracy, and reduce the parameters of the model to facilitate the deployment on hardware devices in practical applications.
Abstract: Ship visible images detection based on computer vision plays an important role in the field of intelligent ship. To increase the model speed, accuracy, and reduce the parameters of the model to facilitate the deployment on hardware devices in practical applications, this study proposed a new model named STD-Yolov5. Firstly, the attention mechanism module of ECA was embedded in backbone to enhance the feature extraction capability of the network. Secondly, GAFPN was designed to reduce the parameters and GFLOPs. Thirdly, to solve the problem of ship-type false detection and missing detection, this paper presented a new receptive field amplification module named GSPP. Finally, replaced the GIoU bounding box regression loss function with a simpler generalisation of α-GIoU to improve the accuracy of the model. Compared to Yolov5, the mAP@.5:.95 of STD-Yolov5 increased by 1.2%, the parameters decreased by 24.85%, and the GFLOPs decreased by 14.46%.

Journal ArticleDOI
TL;DR: In this paper , a dual-riser collision onset criterion (COC) was developed based on the vector form intrinsic finite element method where the Blevins wake model is used to consider the wake effects.
Abstract: ABSTRACT This study aims to investigate the static behaviours of two risers and establish the generalised dual-riser collision onset criterion (COC). The dual-riser model is developed based on the vector form intrinsic finite element method where the Blevins wake model is used to consider the wake effects. The governing equations including a virtual damping force are solved by the central difference method to obtain the static behaviours of risers. Then, the effects of initial spacing, top tension factor and current velocity on the static behaviours of two vertical risers arranged tandem are investigated. Further, the dual-riser COC is established with three non-dimensional parameters by linear-regression analysis. The results show that a larger top tension factor of the upstream riser and a smaller that of the downstream riser is a more effective combination to avoid collisions. The dual-riser COC can be described by a linear function of non-dimensional parameters.

Journal ArticleDOI
TL;DR: In this paper , a large-scale economic analysis of the impact of sulphur abatement on shipping is presented, where different ship types, engine powers, sailing times and fuel prices are analyzed.
Abstract: ABSTRACT Although there are some studies on the impact of Sulphur 2020 on shipping in the literature, large-scale economic analyses are scarce. For this reason, in compliance with sulphur abatement, this study aims to determine the most economical alternatives for shipping companies. First, real data are collected from the maritime industry and scenarios are created regarding different ship types, engine powers, sailing times and fuel prices. In conclusion, using very low sulphur fuel oil alternative for dry cargo ships, hybrid scrubber alternative for crude oil tankers, open-loop scrubber alternative for container ships and hybrid scrubber for Ro-Ro ships are found as economically beneficial in most cases. Last of all, the break-even time from low sulphur fuels to scrubber types is presented to guide shipowners in finding the best alternative with respect to ship ages.

Journal ArticleDOI
TL;DR: In this article , the authors summarized the BSEE decommissioning cost estimates in the shallow water US Gulf of Mexico for each of the main decommissioned stages and to infer unit cost statistics and cost functions in the region.
Abstract: The Bureau of Safety and Environmental Enforcement (BSEE) has collected decommissioning expenditure data from operators in the US Gulf of Mexico since 2016 to estimate the decommissioning liability of federal leases. BSEE uses the collected data to estimate the expected decommissioning cost for every active wellbore, structure, and pipeline segment in federal waters but does not otherwise disclose the statistical results of their data collection efforts or methods employed in cost estimation. The task of this paper is to summarise BSEE decommissioning cost estimates in the shallow water US Gulf of Mexico for each of the main decommissioning stages and to infer unit cost statistics and cost functions in the region. Fixed platform removals are expected to cost on average $977,000 in water depth less than 30 m and up to $3.6 million in water depth from 61 to 122 m, about three times more expensive than caisson removals in similar water depth.