bluuebunny/crossref_metadata_2025_split huggingface dataset:
Autonomous Berthing Motion Planning for Under-Actuated ASV Based on Imagined Sub-Goals and Soft Actor-Critic
Authors: Li Zhiyao , Wang Yiting , Wang Lei 
Published: August 2024

Abstract
Autonomous surface vehicles (ASVs) face limitations in their motion due to the maneuverability and environmental factors. Effective motion planning and control algorithms are essential for achieving autonomous navigation for these vessels. For the autonomous berthing motion planning problem of under-actuated ASVs, this paper proposes an approach based on hierarchical reinforcement learning algorithm that incorporates imagined sub-goals and soft actor-critic (HRL-ISSAC). Three layers of policies named the top-level policy, sub-goal arrival policy and auto-berthing policy are implemented in the algorithm. Throughout the training process, the top-level policy is designed to continuously generate appropriate sub-goals that are less difficult to reach than the ultimate berthing target status for ASV. Then the agent would train the sub-goal arrival policy by effectively addressing sub-goals. The Kullback-Leibler Divergence is utilized to reduce the distance between the distributions of sub-goal arrival policy and auto-berthing policy, thereby narrowing down the scope of action exploration of auto-berthing policy and accelerating its training speed. The hindsight experience replay mechanism is also employed in our algorithm to deal with sparse reward problem and optimize the sample efficiency. In the testing process the auto-berthing policy is solely applied, thus simplifying the structure of HRL. The simulation results show that HRL-ISSAC successfully achieved autonomous berthing guidance for the agent and the berthing trajectories generated by our algorithm take both the kinetics and dynamic constraints of ASV into consideration, which validate the effectiveness of our algorithm.
Study of Hull Shape Optimization Using Self-Blending Method
Authors: Zhichao Hong , Lixin Xu , Xiu Li 
Published: August 2024

Abstract
Aiming at the problems of large number of geometric deformation parameters and large consumption of computational resources in ship hull optimization, this paper proposes a self-blending method, which extracts the characteristic shape of ship profile from the mother ship and is used to blending to form a new profile, thus realizing the three-dimensional surface deformation of the hull with fewer parameters. CFD method and multi-island genetic algorithm are used to optimize the ship hull of a high-speed ship. As to the ship optimized in the paper, 6 blending factors are used to control the blending of the base cross-section extracted from the original ship, and the hull surface is reconstructed from the transverse section generated after blending, and the three-dimensional surface deformation of the hull is realized under the premise of ensuring the smooth of the hull. The objective function (total hull resistance coefficient) is predicted by CFD method, and the uncertainty of the numerical calculation method is verified. For the optimization part, the response surface is introduced as a surrogate model, and the number of calculation conditions is reduced by more than 90%, which greatly reduces the consumption of computing resources. After optimization, the total drag coefficient of the target ship is reduced by 9.76%, which verifies the effectiveness of the method in hull shape optimization.
Study on the Synthetic Fiber Rope Mooring for Floating Offshore Wind Turbines Depending on the Water Depth and Materials of Ropes
Authors: Chujo Toshiki , Kamizawa Ken , Yoshimoto Haruki 
Published: August 2024

Abstract
The floating offshore wind turbines (FOWTs) had started activities as commercial floating wind farms in Europe. Japanese Government released the future plan, which is called “Green Innovation Fund Project (GI)”, to install and operate several FOWTs with large scale wind turbines in some areas around Japanese coast. However, further LCOE (Levelized Cost of Energy) saving, such as the building cost of substructures or operation & maintenance cost, is needed to expand the commercial use of FOWTs. The application of synthetic fiber ropes to FOWTs mooring is expected to contribute to the cost reduction. The light weight is one of the properties of synthetic fiber ropes. It also will be an advantageous aspect at the viewpoint of the harbor protection or the burden reduction of the pier ability.
On the other hand, there are many kinds of materials for synthetic fiber ropes and the characteristics or the descriptions in safety guidelines have wide variety depending on the rope materials. Furthermore, the water depth of the installation site has a large effect on the selection of rope materials. Therefore, many conditions must be considered at the early stage of the FOWTs projects.
The authors carried out the initial design of mooring systems of FOWTs with multiple kinds of rope materials in several water depths. The semisubmersible floater with 15 MW wind turbine was applied to this study. The polyester, nylon and HMPE (High Modulus Polyethylene) ropes were applied in this study. The maximum value of floater offset and the safety factor were considered as design conditions.
We clarified the differences of mooring system specifications and the characteristics of mooring systems and floater offset through the numerical simulations. Furthermore, the differences in the physical quantities of mooring components were revealed in many kinds of mooring conditions which have large effect on the procurement costs.
Research on Coupling Characteristics of AUV Hydrodynamic and Motion Response Under Turbulent Flow Induced by Underwater Dune
Authors: Guo Yu , Li Peng , Jiang Zhiyuan 
Published: August 2024

Abstract
As marine resources continue to be extensively developed, Autonomous Underwater Vehicles (AUVs) have emerged as powerful tools for ocean exploration. In tasks such as near-seabed detection, AUVs are required to operate in close proximity to the seabed. The complex terrain of the seabed amplifies the turbulent characteristics of near-seabed flow fields, affecting the hydrodynamic performance of AUVs. The continuously changing turbulent field induces fluctuations in AUV hydrodynamic coefficients, subsequently influencing the stability of AUV navigation. This study focuses on a typical dune terrain and employs the Large Eddy Simulation (LES) method to simulate the flow field near the dune, calculating the hydrodynamic parameters of AUVs. To obtain the navigation path of AUV in the complex flow field around the terrain and analyze AUV motion stability, a combination of the Dynamic Fluid Body Interaction (DFBI) method and the overset grid method is utilized. This approach releases the three degrees of freedom in AUV motion, emphasizing translational displacements in the Cartesian coordinates, as well as pitch phenomena during AUV’s motion. The results provide insights into hydrodynamic changes during AUV navigation and motion deviation trajectories. The findings serve as a reference for the maneuverability performance of AUVs.
Numerical Modeling of a Motion-Neutralized Floater Concept for Maritime Operations
Authors: Jaculli Marcelo Anunciação , Viswanathan Savin , Holden Christian , Leira Bernt Johan , Sangesland Sigbjørn 
Published: August 2024

Abstract
For continuous operation in harsh sea conditions, such as those seen in the North and Norwegian seas during the winter season, a floater must demonstrate reduced amplitudes of motion. A concept of a motion-compensations mechanism has been proposed that can cancel, or at least diminish, the level of such motions. In this context, a three-column asymmetric semisubmersible floater with passive motion-control technology, dubbed “Sakayan”, is discussed. This new floater concept can be used for offshore wind power generation, as well as for well interventions. Passive control is performed through the usage of air chambers, which are placed inside each of its three columns. This is a continuation of previous research efforts to investigate the effectiveness of air chambers to compensate for heave motion. This work aims to further study the dynamics of this floater and verify its capability to ameliorate the heave and pitch/roll motions. Numerical simulations are carried out using commercial software in the frequency and time domains. Results show that the presence of air chambers reduces the amplitude of motion for most of the six degrees of freedom and wave/wind incidence angles, albeit complete elimination is not achieved. Further studies are necessary concerning the application of an active control system for the present floater concept.
Reducing the Influence of Localized Large Stiffness Compartments in Longitudinal Bending Moment Identification
Authors: Weng Zhujing , Gan Jin , Xu Gengdu , Chen Yonghan 
Published: August 2024

Abstract
The capability of hulls to withstand longitudinal bending moments has been a subject of continuous research. Longitudinal bending moment identification is an essential aspect of the ship structural health monitoring. This study aims to investigate the effect of localized large stiffness compartments on the accuracy of longitudinal bending moment identification and proposes an effective method to improve this accuracy. A numerical study is carried out with a box-beam model as the research object to investigate in detail the effect of localized large stiffness compartments on the spatial distribution of model stresses, and a modified method of longitudinal bending moment identification with correction coefficient is introduced to mitigate the impact of localized large stiffness compartments on identification accuracy. Numerical results indicate that localized large stiffness compartments have a significant impact on the side stress distribution of the model. The stress distribution above the top deck of the compartment is linear, while below it is nonlinear, making it challenging to achieve the desired identification accuracy using longitudinal bending moment identification based on hull bending theory. Compared with the conventional method, the modified method can significantly improve the identification accuracy of the longitudinal bending moment under the localized large stiffness compartment structure, with identification error below 5%. Therefore, implementing this method in practical engineering is highly promising and has broad application prospects.
Ride Control System Effects on Motion, Slam Load, and Passenger Comfort of High-Speed Catamarans: An Experimental Study in Irregular Waves
Authors: Javanmardemamgheisi Ehsan , Mehr Javad A. , Holloway Damien S. , Davis Michael R. , Ali-Lavroff Jason 
Published: August 2024

Abstract
In recent years, the demand for efficient waterborne transportation has led to the development of high-speed catamarans. However, increased operating speeds result in elevated ship motions, making ride control systems desirable for passenger comfort, crew workability, and operational efficiency. This paper presents comprehensive towing tank experiments on a 2.5 m hydroelastic segmented catamaran model of a 112 m Incat Tasmania high-speed catamaran. These tests assess the impact of different ride control algorithms on the model’s motion and load responses, as well as passenger comfort in irregular head sea waves. The model featured a ride control system with a centrally positioned bow-fitted T-Foil and two stern-mounted stern tabs.
The study analysed ship motion responses, centre bow slam events, and the motion sickness dose value at specific longitudinal locations of the passenger cabin. The results showed that, in moderate waves, a nonlinear pitch control algorithm significantly improved performance, reducing RMS pitch and heave motions by around 32% and 29%, respectively, peak pitch and heave RAOs by 41% and 31%, respectively, and motion sickness at the forward position by 70%. The structural load analysis demonstrated a substantial reduction in the number of slams of 96% and 50% in small and large seas, respectively, using a nonlinear pitch control algorithm. These results demonstrate the considerable potential for further enhancing passenger comfort, structural response, and operational efficiency of high-speed catamarans using an effective ride control algorithm.
ISSC 2025 Committee III.1 - Compressive Test of a Transversely Stiffened Thin-Plated Structure With Expected Early Nonlinear Response Prior to the Ultimate Capacity: Preliminary Comparison of the Numerical Results
Authors: Gaiotti Marco , Barsotti Beatrice , Brubak Lars , Chen Bai-Qiao , Darie Ionel , Georgiadis Dimitris , Ishibashi Kinya , Korgesaar Mihkel , Lv Yining , Nahshon Ken , Paredes Marcelo , Ringsberg Jonas , Schipperen Ingrid , Tatsumi Akira , Vaz Murilo , Wang Yikun , Zamarin Albert , Zhan Zhihu 
Published: August 2024

Abstract
The maritime industry is increasingly utilizing high-strength steels for lightweight ship design. While enhanced yield strength is advantageous, these steels retain the same Young’s modulus as lower strength steel grades posing challenges in designing slender structures, particularly concerning structural buckling strength. In longitudinal stiffened ship structures, transverse buckling effects, though less significant than longitudinal stresses, can be difficult to predict. Addressing this, the regulatory framework for verifying the buckling of transversely stiffened panels for ships is a topic of substantial international discussion. A research project supported by Fincantieri led the University of Genova to develop a test configuration assessing a slender ship structure’s response to transverse loads. The ISSC 2022-2025 Committee III.1 Ultimate Strength is utilizing this test configuration to conduct a numerical benchmark in three phases, with each phase gradually revealing additional experimental data to the study participants. The benchmark aims to predict the entire end-shortening curve as well as ultimate load to understand load redistribution and quantify energy absorption for dynamic events. This paper presents the preliminary results from Phase 1, focusing on diverse modeling strategies impacting outcomes, including element type, mesh size, and interpretation of initial geometric imperfections among participants in the benchmark study.
Friction-Induced Vibration and Noise in Water-Lubricated Stern Bearings: A Comprehensive Review of Mechanisms and Design
Authors: Yang Chaozhen , Kuang Fuming , Wang Ting , Chen Meixia 
Published: August 2024

Abstract
Water-lubricated stern bearings are critical components of marine propulsion systems, influencing ship stability under extreme conditions such as low speed and heavy load. The acoustic stealth performance of underwater vehicles is closely tied to the friction-induced vibration and noise of the bearing system. Extensive research has been conducted to investigate the underlying mechanisms of these phenomena and explore novel materials and structural designs to address them. However, a complete resolution has yet to be achieved. While a significant portion of scholarly attention is dedicated to the design of novel bearing materials, encompassing ceramic, modified rubber, and polymer bearings, and innovative bearing structures such as micro-texture, honeycomb, and flume structures, there exists a critical gap in our understanding of the intricate relationship between nonlinear vibrations induced by friction lubrication and the resultant effects on shafting and overall ship vibration. Further research is warranted to unravel the nuanced connections between these elements, fostering a more comprehensive comprehension of bearing dynamics in the context of ship performance. This paper presents a comprehensive review that encompasses the generation mechanisms of friction-induced vibration and noise in water-lubricated stern bearings, along with an analysis of innovative structural design schemes and control strategies aimed at minimizing noise. The limitations of existing technologies are summarized, and potential future trends are identified, establishing a robust theoretical foundation for optimizing water-lubricated bearings and developing “silent” water-lubricated stern tube bearings.
Optimization of Bow Thruster Openings for Improved Hydrodynamic Performance
Authors: Ciortan Cosmin , Caizzi Antonio 
Published: August 2024

Abstract
Bow thrusters are a common feature of ships nowadays and come with the undesired effect of creating relatively large openings at the bow of the ship, increasing the resistance of the hull. The most common solution for mitigating the increase in hull resistance, and at the same time protecting the thruster from ingestion of large objects, is to use grids which are generally placed perpendicular to the local flow. Until the advent of Computational Fluid Dynamics (CFD), the effect of the grids on resistance could not be properly assessed due to the difficulty (or rather impossibility) of scaling their contribution in the towing tank, on the one hand, and the perceived negligible influence, on the other hand. Since their effects are mainly viscous, it is understandable why towing tank testing will not provide the actual picture. In the present paper, CFD is used to study several ships with bow thruster openings, at operating speed. Optimization solutions are presented and the effect of the grids as built is assessed against alternative solutions. The simulations are carried out in full scale, in three steps: the hull with completely closed tunnels; hull “as built”; hull with optimized bow thruster opening grids. The results indicate that in all studied cases, the grids are detrimental to resistance and savings can be obtained by using other solutions or different placement or orientation.
Assessment of Different Layouts of Rod Reinforcement Mesh in Stiffening Fish Cages Under Wave Loads
Authors: Ma Mingyuan , Zhang Xinyu , Chu Yunil , Wang Chien Ming , Zhang Hong 
Published: August 2024

Abstract
Flexible or semi-rigid fish net cages made from high-density polyethylene (HDPE) material typically experience significant deformation and volume reduction under strong hydrodynamic loads. This paper investigates the performance of two layouts of rod reinforcement mesh used to stiffen net cages against deformation under hydrodynamic loads. The first layout forms a square mesh pattern while the second layout forms a diamond mesh pattern. The finite element software AquaSim was used to simulate the hydroelastic responses of these flexible fish cages that are stiffened by rod reinforcement mesh under wave actions. The deformation and volume reductions of the fish cage were compared for the two layout patterns of rod reinforcement. The results indicate that, for fish cages supported by cubic HDPE frames, a diamond mesh layout of rod reinforcement performs better in stiffening the fish cage against deformation than a square mesh layout but results in a greater internal force response within the structure near the mooring constraint end. Also, when compared to a square mesh layout, the diamond layout requires less material for the rod reinforcement mesh used for the cubic fish cages. In addition, parametric studies indicate that the longitudinal beams of the cage frame based on the diamond mesh layout have more pronounced shear force and torsional moment, but they have smaller axial force under shorter wave actions. This study provides valuable reference for engineers in designing more optimal fish cages.
Crystal Plasticity Finite Element Modeling of Elastic-Viscoplastic Deformation of Ice Single Crystals
Authors: Dai Huiling , Di Shaocheng , Xue Yanzhuo 
Published: August 2024

Abstract
Ih ice single crystals with densely packed hexagonal structure exhibit elastic-viscoplasticity anisotropy under low strain rate loading conditions, which is directly related to the crystal structure. In order to reflect the elastic-viscoplastic deformation properties of ice single crystals, a crystal plasticity finite element (CPFE) numerical model considering loading rate and crystal orientation dependence based on dislocation slip mechanism was established. In the model, Hooke’s law is followed for elastic deformation, and Schmidt’s law is used for plastic deformation to establish the relationship between shear strain rate and shear stress on different slip systems. The calculation accuracy of the model was verified by comparing with the published results of constant strain rate deformation of ice single crystals. On this basis, the effect of crystal orientation on the deformation of ice single crystals was investigated through the loading simulation at different angles (0°, 15°, 30°, 45°, 60°, 75°, 90°) with the C-axis, and the mechanical response, the activation condition of slip systems and slip ability were analyzed when slip occurred under different crystal orientations. The results show that the numerical simulations of ice single crystals based on the established CPFE model can reasonably characterize the elastic-viscoplastic deformation characteristics. Except for crystal orientations of 0° and 90°, all ice single crystals under other crystal orientations exhibit stress softening characteristics, which are related to the activation of basal slip systems. Under the same deformation conditions, basal slip is most easy to occur. This work can provide a theoretical model at crystal scale for the establishment of multi-scale constitutive relations of polycrystalline ice based on microstructure evolution.
An Approach for Obtaining Dynamic Responses of Slender Marine Structures Assisted by Generalized Artificial Neural Networks
Authors: Rodrigues Thiago , Ângelo Gonçalves de Lacerda Thiago , Mattos Gonzalez Gabriel , Volnei Sudati Sagrilo Luis , Carneiro Campello George , Figueira De Souza Rodolfo , Brun Coser Tiago 
Published: August 2024

Abstract
Fatigue life evaluation of slender marine structures, such as flexible lines, are usually performed through stochastic dynamic analyses in the time domain. Traditionally, these analyses are performed in order to obtain the dynamic responses’ time series of the risers (axial force and bending moments). These analyses are usually conducted through Finite Element Method (FEM) which presents high degree of confidence in its results, but also can generate high computational costs. So, many works seek alternative methods to obtain these dynamic responses and some of them have introduced the use of artificial neural networks (ANN) in this process to obtain computational gain. These works presented interesting results using a hybrid FEM-ANN models, but most of them treat each riser and environmental condition separately, that is, the models are trained individually for each response evaluation. The present work is an extension of the previous one [1] and its main goal is to develop a network that from just one single training it is able to generate accurate predictions of the axial tensions and bending moments time series of flexible risers connected to different platforms and also for different wave load conditions. The model is tested for a free-hanging flexible riser. The network’s results are compared to those from the full FEM-based numerical simulations to show the accuracy and robustness of the presented model.