Large-scale Ship Research Articles

Meshfree simulations of large scale ductile fracture of stiffened ship hull plates during ship stranding

In this work, we have developed a systematic computational methodology to directly simulate the ductile fracture of ship hull structure during ship stranding based on the meshfree Reproducing Kernel Particle Method. The whole computational algorithm has four parts: The first part is establishing interpolation shape functions of RKPM; the second part is the meshfree computational algorithm for simulation of three-dimensional crack propagation; The third part is a computational algorithm for detecting contact and calculating interaction force during ship stranding or grounding, and the last part is the constitutive modeling and update procedure during simulation for ship hull structure material. In this work, we adopt the Gurson-Tvergaard-Needleman model to model large scale ship hull structures. To validate above modeling and computational methodology, a large scale simulation of ship hull structure indentation test is carried out to directly comparing with the experimental test conducted by Alsos and Amdahl (Int J Impact Eng 36(6):799–807, 2009). The comparison between numerical results and experimental test results have been carefully analyzed. Subsequently, the simulations of simplified stranding processes in three different cases are performed. The results from numerical simulations indicate that the proposed computational algorithm is capable of capturing the plastic deformation and damage of ship hull structure subjected to grounding impact.

Large-scale Ship Fault Data Retrieval Algorithm Supporting Complex Query in Cloud Computing

ABSTRACT Zhang, S., 2019. Large-scale ship fault data retrieval algorithm supporting complex query in cloud computing. In: Hoang, A.T. and Aqeel Ashraf, M. (eds.), Research, Monitoring, and Enginee...

Dense Attention Pyramid Networks for Multi-Scale Ship Detection in SAR Images

Synthetic aperture radar (SAR) is an active microwave imaging sensor with the capability of working in all-weather, all-day to provide high-resolution SAR images. Recently, SAR images have been widely used in civilian and military fields, such as ship detection. The scales of different ships vary in SAR images, especially for small-scale ships, which only occupy few pixels and have lower contrast. Compared with large-scale ships, the current ship detection methods are insensitive to small-scale ships. Therefore, the ship detection methods are facing difficulties with multi-scale ship detection in SAR images. A novel multi-scale ship detection method based on a dense attention pyramid network (DAPN) in SAR images is proposed in this paper. The DAPN adopts a pyramid structure, which densely connects convolutional block attention module (CBAM) to each concatenated feature map from top to bottom of the pyramid network. In this way, abundant features containing resolution and semantic information are extracted for multi-scale ship detection while refining concatenated feature maps to highlight salient features for specific scales by CBAM. Then, the salient features are integrated with global unblurred features to improve accuracy effectively in SAR images. Finally, the fused feature maps are fed to the detection network to obtain the final detection results. Experiments on the data set of SAR ship detection data set (SSDD) including multi-scale ships in various SAR images show that the proposed method can detect multi-scale ships in different scenes of SAR images with extremely high accuracy and outperforms other ship detection methods implemented on SSDD.

Distributed Model Predictive Control of Steam/Water Loop in Large Scale Ships

In modern steam power plants, the ever-increasing complexity requires great reliability and flexibility of the control system. Hence, in this paper, the feasibility of a distributed model predictive control (DiMPC) strategy with an extended prediction self-adaptive control (EPSAC) framework is studied, in which the multiple controllers allow each sub-loop to have its own requirement flexibility. Meanwhile, the model predictive control can guarantee a good performance for the system with constraints. The performance is compared against a decentralized model predictive control (DeMPC) and a centralized model predictive control (CMPC). In order to improve the computing speed, a multiple objective model predictive control (MOMPC) is proposed. For the stability of the control system, the convergence of the DiMPC is discussed. Simulation tests are performed on the five different sub-loops of steam/water loop. The results indicate that the DiMPC may achieve similar performance as CMPC while outperforming the DeMPC method.

Comparison of large-scale ship exhaust emissions across multiple resolutions: From annual to hourly data

Ship exhaust emissions need to be calculated at fine spatial and temporal resolutions because chemical transport processes depend on meteorological conditions that have a high degree of spatial and temporal variability. These emissions can also occur in environments that are affected by spatially and temporally varying emissions from other sources. Ship exhaust emissions are calculated using activity data from the Automatic Identification System. The activity data are combined with ship specific technical data. Hourly emissions are obtained for 2014 over the region within 300 km of Sydney at approximately 1 km resolution. These data are aggregated regionally and by vessel type to examine variability at different temporal resolutions. Cruise ship emissions vary both seasonally and diurnally, with low activity in winter and high activity in spring and summer. Diurnal variability is associated with a preference for hoteling at berth during the day and cruising at sea overnight. Emissions from the Sydney Harbour ferries have a strong but more complex diurnal variation that is affected by work related commuting. Monthly variability is also described for other ship types that visited the four major ports in the region. Spatial cell activity hours are analysed to explain large differences in the average spatial extent of the emissions at different temporal resolutions, the accuracy with which the hourly emission rates are estimated using longer term emissions, and the suitability of generalised temporal profiles to describe the emissions data. Regression analysis is used to model the spatial extent of the hourly and daily emissions.

Large-Scale Automatic Vessel Monitoring Based on Dual-Polarization Sentinel-1 and AIS Data

This research addresses the use of dual-polarimetric descriptors for automatic large-scale ship detection and characterization from synthetic aperture radar (SAR) data. Ship detection is usually performed independently on each polarization channel and the detection results are merged subsequently. In this study, we propose to make use of the complex coherence between the two polarization channels of Sentinel-1 and to perform vessel detection in this domain. Therefore, an automatic algorithm, based on the dual-polarization coherence, and applicable to entire large scale SAR scenes in a timely manner, is developed. Automatic identification system (AIS) data are used for an extensive and also large scale cross-comparison with the SAR-based detections. The comparative assessment allows us to evaluate the added-value of the dual-polarization complex coherence, with respect to SAR intensity images in ship detection, as well as the SAR detection performances depending on a vessel’s size. The proposed methodology is justified statistically and tested on Sentinel-1 data acquired over two different and contrasting, in terms of traffic conditions, areas: the English Channel the and Pacific coastline of Mexico. The results indicate a very high SAR detection rate, i.e., >80%, for vessels larger than 60 m and a decrease of detection rate up to 40 % for smaller size vessels. In addition, the analysis highlights many SAR detections without corresponding AIS positions, indicating the complementarity of SAR with respect to cooperative sources for detecting dark vessels.

Critical Success Factors in Marine Safety Management in Shipping Industry

Chen, C.; Chiang, Z.; Liu, Y., and Zeng, X., 2018. Critical success factors in marine safety management in shipping industry. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 846–850. Coconut Creek (Florida), ISSN0749-0208.About three-fourth of global flow of cargo is currently transported through shipping. The boom of international trade, which mainly depends on marine transportation, in past years has shipping industry become the economic focus in coastal countries. Along with the economic development and increasing global trade, the increasing number of ships and large-scale ships, accidents at sea are not eliminated with improving marine technology. It is therefore important for shipping industry, through management, establishing safety management mechanism conforming to regulations and suitable for ships to reduce operational risks and further eliminate accidents caused by personal factors in order to create business performance of enterprises. Shipping industry is the research object in this study. Supervisors and employees of Fujian Shipping Company are sampled for the questionnaire survey. Total 300 copies of questionnaire are distributed, and 256 valid copies are retrieved, with the retrieval rate 85%. The research results are concluded as followings. (1) From the survey, organizational planning was mostly emphasized in safety management in shipping industry. (2) From the overall weights of evaluation indicators, tope five indicators, among 17 evaluation indicators, are competent personnel, censorship, regulation compliance, sound system, and administrative support. Suggestions are proposed according to the results, expecting to analyze the critical factors in the establishment of safety management systems in shipping industry. Proper strategic suggestions are also proposed to solve the problems encountered in safety management systems to enhance the effectiveness of safety management.

Welding Residual Stress Effect in Fracture Toughness.

The thickness of steel plates used for large structures has been increasing with the rapid increase in the size of welding structures. The growing capacity of large-scale ships, such as container ships, has led to an increase in the thickness and strength of steel plates for shipbuilding. The steel plate toughness and resistance to brittle fractures tend to decrease for thick plates because of the so-called thickness effect. This study uses 80-mm-thick steel plates and two welding processes (i.e., flux cored arc welding process and electron gas welding process) to produce full-thickness weld joints. The welding residual stress in both welded joints is measured to evaluate the brittle crack propagation path. This study aims to investigate the effect of welding variables on the crack arrest toughness and crack propagation path of thick steel-plate welds. The thick steel plate has a high possibility in brittle fracture. A quantitative analysis is conducted through a temperature-gradient ESSO test to clarify the effect of the welding variables on the flux cored arc welding and electron gas welding process joints of steel plates with 50 and 80 mm thicknesses. The welding residual stress is also measured to evaluate the welding residual stress effect in both welding processes on the brittle crack propagation path using a neutron science analysis.

DAB‐based PET in MVDC traction and shipboard applications with distribution and redundant control

Medium-voltage DC (MVDC) grid has drawn more interest in the application of traction and large-scale ships, for its lower loss, higher reliability, higher controllability and simpler system architecture. DC breaker and DC distribution are the key elements in the MVDC grid, and the power electronic transformers (PETs) have shown great advantage in the MVDC grid for its relatively smaller volume and higher flexibility compared to the traditional line transformers and AC/DC converters. In this study, a distribution DC PET based on input series output parallel dual active bridge (DAB) is proposed in the application of power supply system in traction and large scale ships. The DC PET consists of 12 DABs with an input voltage of 10 kV and the output voltage of 380 V. Strategies are proposed for distributed voltage balancing and redundancy control in the proposed PET. Simulations were done in MATLAB/Simulink. In the simulation, waveforms in the normal working conditions and the module fault status is shown, and the result shows that the proposed DC PET has great controllability and flexibility and by adding redundant modules, it keeps great reliability while fault occurs.

Nonlinear Predictive Control Applied to Steam/Water Loop in Large Scale Ships

Abstract In steam/water loop for large scale ships, there are mainly five sub-loops posing different dynamics in the complete process. When optimization is involved, it is necessary to select different prediction horizons for each loop. In this work, the effect of prediction horizon for Multiple-Input Multiple-Output (MIMO) system is studied. Firstly, Nonlinear Extended Prediction Self-Adaptive Controller (NEPSAC) is designed for the steam/water loop system. Secondly, different prediction horizons are simulated within the NEPSAC algorithm. Based on simulation results, we conclude that specific tuning of prediction horizons based on loop’s dynamic outperforms the case when a trade-off is made and a single valued prediction horizon is used for all the loops.

Effect of Control Horizon in Model Predictive Control for Steam/Water Loop in Large-Scale Ships

This paper presents an extensive analysis of the properties of different control horizon sets in an Extended Prediction Self-Adaptive Control (EPSAC) model predictive control framework. Analysis is performed on the linear multivariable model of the steam/water loop in large-scale watercraft/ships. The results indicate that larger control horizon values lead to better loop performance, at the cost of computational complexity. Hence, it is necessary to find a good trade-off between the performance of the system and allocated or available computational complexity. In this original work, this problem is explicitly treated as an optimization task, leading to the optimal control horizon sets for the steam/water loop example. Based on simulation results, it is concluded that specific tuning of control horizons outperforms the case when only a single valued control horizon is used for all the loops.

大規模モデルに適用可能な流体-構造連成を考慮した船体振動解析手法の開発 ――第 1 報：直接時間積分による船体振動解析手法の構築と簡易箱モデルによる検証――

大規模モデルに適用可能な流体-構造連成を考慮した船体振動解析手法の開発 ――第 1 報：直接時間積分による船体振動解析手法の構築と簡易箱モデルによる検証――

大規模モデルに適用可能な流体-構造連成を考慮した船体振動解析手法の開発 ――第 2 報：大規模モデルへの適用――

大規模モデルに適用可能な流体-構造連成を考慮した船体振動解析手法の開発 ――第 2 報：大規模モデルへの適用――

Nonlinear Antiswing Control of Offshore Cranes With Unknown Parameters and Persistent Ship-Induced Perturbations: Theoretical Design and Hardware Experiments

In practical applications, offshore cranes are widely utilized on large scale ships to accomplish the tasks of transferring cargos from one ship to another or between ships and harbors. Compared with traditional land-fixed cranes, offshore cranes work in noninertial (ship) frames and their movements are significantly influenced by such complicated disturbances as sea waves, etc. Hence, the control issue of offshore cranes presents much more challenges. At present, existing controllers for offshore cranes are designed based upon linearized dynamics, and they need the accurate values of the plant parameters. However, the values of the parameters, including cargo/jib masses, are usually difficult to measure or even unknown, which makes exact gravitational force compensation difficult and unavoidably results in positioning errors for luffing and hoisting/lowering control. To deal with these practical issues, we suggest a novel model-parameter-free control approach to achieve effective control for underactuated offshore crane systems. By constructing an elaborate storage function, we provide a complete Lyapunov-based stability analysis. As far as we know, this paper provides the first control strategy to asymptotically regulate an offshore crane system subject to parametric uncertainties and ship-induced perturbations, which is developed without simplifying the original nonlinear dynamic equations. At last, a series of experimental results, carried out on a self-built offshore crane hardware platform, are presented to validate the effectiveness and robustness of the presented control scheme.

A Robust PID Autotuning Method for Steam/Water Loop in Large Scale Ships

During the voyage of the ship, disturbances from the sea dynamics are frequently changing, and the ship’s operation mode is also varied. Hence, it is necessary to have a good controller for steam/water loop, as the control task is becoming more challenging in large scale ships. In this paper, a robust proportional-integral-derivative (PID) autotuning method is presented and applied to the steam/water loop based on single sine tests for every sub-loop in the steam/water loop. The controller is obtained during which the user-defined robustness margins are guaranteed. Its performance is compared against other PID autotuners, and results indicate its superiority.

Sea-trial verification of ultrasonic antifouling control

An ultrasonic antifouling treatment was applied to a 96,000 m3 class drill-ship to verify its feasibility through a sea-trial. Soon after the hull cleaning had been performed, six ultrasonic projectors were evenly deployed around the starboard shell plate. Driven by a 23 kHz sinusoidal ultrasound in an intermittent manner, the projectors emitted a high-intensity sound reaching 214 dB at the source level causing cavitation around the adjacent water and eventually deterring the settlement of marine fouling organisms. Underwater photographs acquired after four months showed fairly clean slabs on the starboard side, but heavy fouling on the port side. This experiment revealed that ultrasound treatment is a promising method for inhibiting fouling accumulation, even for large-scale ship applications.

Research on Intelligent Diagnosis Method for Large-Scale Ship Engine Fault in Non-Deterministic Environment

Abstract Aiming at the problem of inaccurate and time-consuming of the fault diagnosis method for large-scale ship engine, an intelligent diagnosis method for large-scale ship engine fault in non-deterministic environment based on neural network is proposed. First, the possible fault of the engine was analyzed, and the downtime fault of large-scale ship engine and the main fault mode were identified. On this basis, the fault diagnosis model for large-scale ship engine based on neural network is established, and the intelligent diagnosis of engine fault is completed. The experiment proved that the proposed method has high diagnostic accuracy, engine fault diagnosis takes only about 3s, with a higher use value.

Design and off-design models of single and two-stage ORC systems on board a LNG carrier for the search of the optimal performance and control strategy

A diesel-electric propulsion system is generally used in large scale ships to allow a free placement of Internal Combustion Engines (ICEs), to acoustically decouple engines and hull, and reduce total weight and volume. On long voyages, the speed of a vessel can be more or less constant. Thus, to a first approximation, it can be considered that the engines operate most of the time at steady-state conditions. On this basis, Organic Rankine Cycle (ORC) systems can be conveniently installed aboard to generate additional electric power by recovering ICEs waste heat and increase in turn the overall system efficiency. The ICEs-ORC combined cycle system has to be designed properly to maximize the work production and guarantee at the same time a stable operation during both transient and steady-state working conditions.This paper presents the design and off-design dynamic and steady-state models of three ORC system configurations that exploit the waste heat of four dual fuel diesel ICEs on board a LNG carrier. One single-stage and two (subcritical or supercritical) two-stage ORC system configurations are considered. The available heat is taken from charge air, jacket and oil cooling systems, while the exhaust gases are not considered to be available being already used for other ship internal needs. Dynamic simulations are employed to define the control strategies that lead to stable operation of all the considered ORC system configurations after transients of the ship operation. Steady-state off-design models are then used to identify the best system design point taking into account the real ship operation during a reference year. Results show that the best performing single-stage ORC is designed for a ship speed of 16.5 knots on loaded voyage, and has an annual work production of 1665.8MWh with a peak thermal efficiency of 6.5%. The supercritical configuration reaches the best performance among the two-stage ORC systems, achieving a work production of 2306.6MWh and a thermal efficiency of 12.6% at 15.5 knots.

Experimental and theoretical study of magnetohydrodynamic ship models.

Magnetohydrodynamic (MHD) ships represent a clear demonstration of the Lorentz force in fluids, which explains the number of students practicals or exercises described on the web. However, the related literature is rather specific and no complete comparison between theory and typical small scale experiments is currently available. This work provides, in a self-consistent framework, a detailed presentation of the relevant theoretical equations for small MHD ships and experimental measurements for future benchmarks. Theoretical results of the literature are adapted to these simple battery/magnets powered ships moving on salt water. Comparison between theory and experiments are performed to validate each theoretical step such as the Tafel and the Kohlrausch laws, or the predicted ship speed. A successful agreement is obtained without any adjustable parameter. Finally, based on these results, an optimal design is then deduced from the theory. Therefore this work provides a solid theoretical and experimental ground for small scale MHD ships, by presenting in detail several approximations and how they affect the boat efficiency. Moreover, the theory is general enough to be adapted to other contexts, such as large scale ships or industrial flow measurement techniques.

Challenges and solutions for ship recycling in China

The world ship recycling centre has shifted from developed countries to developing countries in Asia. However, Chinese ship recycling companies are experiencing a recession in the ship recycling market and intense price competition from South Asian countries. In this study, Chinese economic environment is analysed, including depressed recycled steel market and price, non-preferential tax policy and high investment cost of ship recycling yards. This paper presents Chinese major laws and regulations related to the ship recycling industry for environmental protection and the workers’ health and safety. From the comparison between Chinese laws and international conventions, we find that no specific enforcing mechanism exists in the Chinese ship recycling industry. However, Chinese large-scale ship recycling yards have been taking advanced practices including site environmental protection, dismantling procedures and technologies, and safety management. Arising from this study, several strategies and solutions for Chinese ship recycling facilities are recommended.