bluuebunny/crossref_metadata_2025 huggingface dataset:
A Novel Approach of Data Science Incorporating Physical Knowledge for Early Stuck Pipe Detection
Authors: Inoue Tomoya , Kaneko Tatsuya , Nakagawa Yujin , Wada Ryota , Abe Shungo , Yasutake Gota
Published: August 2024

Early detection of stuck pipes during drilling operations is crucial and challenging. Some of the existing studies on the stuck pipe detection have adopted supervised machine learning approaches that employ datasets for “stuck” and “normal”. However, for early detection before the occurrence of stuck pipe, the application of ordinal binary classification in supervised machine learning has presented several elemental concerns, such as limited stuck pipe data, and lack of an exact “stuck sign” before occurrence. Our previous studies proposed unsupervised machine learning approaches using data on the normal activities with long short-term memories and autoencoder, the mixture probability model, and graph attention model, and presented the possibility of predicting a stuck pipe. On the other hand, there observed false positives responding the operation of drilling equipment or changes in drilling data.

We introduce a data science approach, including machine learning, incorporating physical knowledge to overcome frequent false positives. This study initially introduces the stuck pipe predictions using unsupervised machine learning approaches, and a typical false positive case. Subsequently, we present machine learning integrating physical knowledge and demonstrate early stuck pipe detection using field data containing stuck pipe events. The results show significant suppression of false positives. Our machine learning approach is expected to contribute to considerable reduction of nonproductive time in drilling operations, potentially preventing well abandonment.
Influence of Configuration of Hemispherical Artificial Reefs on Scouring Around Offshore Wind Power Pile Foundation
Authors: Han Shuwei , Li Dawei , Yang Mingda , Tang Yanli , Zhao Fenfang , Huang Liuyi
Published: August 2024

The burgeoning integration of offshore wind power and marine ranching underscores a pivotal avenue for the harmonized advancement of marine fisheries and sustainable energy. Central to this integration is the strategic deployment of artificial reefs (ARs), especially for mitigating scour around offshore wind power pile foundation (OWF). This study pioneers a three-dimensional numerical model, leveraging the prototype of China’s first offshore wind power-marine ranch demonstration project. Employing the Reynolds-averaged Navier-Stokes equations and sediment transport dynamics, the model intricately simulates fluid motion and sediment scour in the proximity of ARs and OWFs.

The numerical results indicate that the proximity between a single hemispherical AR and OWF significantly dictates scour severity, with closer ARs (G/D < 2) exacerbating scour due to underdeveloped wake regions and increased turbulence. Conversely, at greater distances (G/D ratios of 2 and 3), ARs fully develop protective wake regions, effectively reducing scour depth by 37% and scour volume by 42% around the OWF. The study further reveals that specific arrangements of ARs can either mitigate or intensify scour effects. While parallel configurations of ARs demonstrate a notable reduction in scour depth and volume, this protective efficacy wanes with increasing P/L ratios, ceasing beyond a P/L ratio of 4. In contrast, a tandem arrangement of ARs, especially at a G/D ratio of 1, sharply intensifies scour volume around OWF. The findings are instrumental in guiding the design and arrangement of ARs in marine environments, aiming to enhance the structural stability of OWFs and contribute to the ecological harmony of marine systems.
Undrained Load-Carrying Capacity of Subsea Foldable Mudmat Foundations Under General V-H-M Loading
Authors: Feng Xiaowei , Li Xiaolong , Sun Liqiang
Published: August 2024

With offshore oil and gas developments moving into deep water, the size of mudmats foundations has been increasingly large, exceeding the handling capacity of the installation vessels. The foldable design can effectively avoid the constraints by the stinger or the moon pool. The analytical and numerical solutions of the undrained load-carrying capacity of shallow foundations are mostly available for single (isolated) foundations, and not feasible for design of the foldable mudmats. The undrained bearing capacity and failure mechanisms of the foldable mudmats depend significantly on the foundation spacing and the soil strength profiles. Finite-element simulations are carried out to determine the undrained load-carrying capacity of the foldable mudmats under general loading. Results are presented in the form of failure envelopes under combined V-H, V-M, H-M and V-H-M loading. The load-sharing mechanisms of two rigidly connected mudmats are investigated. Soil failure mechanisms are illustrated for the representative loading paths of the foldable mudmats, and their dependency on the foundation spacing and the soil strength heterogeneity is systematically examined. Based on the revealed failure mechanisms, the methods are established for predicting the undrained load-carrying capacity of the foldable mudmats. Comparisons of the predictions with the FE results indicate that the proposed method is highly credible to assist the foundation design in practice.
Hydrodynamic Performance of a Pitching Circular Motion Hydrofoil for Tidal Current Energy Harvest
Authors: Yao Huilan , Zhang Boxiao , Zhou Xin
Published: August 2024

Considering that if a pitching hydrofoil moves in a circle, the mechanical structure of the turbine can be further simplified, which is much simpler than a traditional oscillating hydrofoil tidal current turbine, therefore the performance of a pitching hydrofoil with such simple trajectory has attracted our interest. In this paper, numerical method was adopted to simulate a pitching circular motion hydrofoil with variety of motion parameters. Before that, the method was verified and validated. Then, instantaneous hydrodynamic forces, vortex flow field and power coefficients of the hydrofoil were studied. More importantly, the effect of pitch amplitude and circular motion frequency was investigated. Results show that, the vertical force (lift) is the main power for the hydrofoil to harvest energy. For most of the time in one motion period, the horizontal force and pitch moment do negative work. The favorable interaction between vortex and hydrofoil can increase the positive work done by the lift and reduce the negative work done by horizontal force and pitch moment, thus improving the energy harvest efficiency. There are optimal values for the two main motion parameters, which can maximize the energy harvest efficiency. When the pitch amplitude is 75 degrees and the reduced frequency is 0.14, the efficiency can reach more than 40%.
Suppression of Vortex Shedding Past a Cylinder at Higher Reynolds Numbers: A Numerical Study
Authors: Parida Aniket , Srineash V. K. , Behera Manasa Ranjan
Published: August 2024

Vortex-induced vibrations (VIV) are induced on a bluff body when it is introduced to a fluid flow, which produces vortex shedding. Many times, the presence of VIV attributed due to vortex shedding is considered undesirable since it leads to fatigue induced damage on structural elements. The phenomenon of VIV is an important consideration, especially for offshore structures which are usually made of cylindrical members. The present study investigates the suppression of vortex shedding past a fixed cylinder using streamlined fairings and short-tailed fairings using a Computational Fluid Dynamics (CFD) solver based on Reynolds Averaged Navier-Stokes (RANS) equation. Fairings are relatively neutrally buoyant elements that are installed along the axis of long circular cylinders in order to lower drag force and to minimize VIV. The work aims at studying the vortex shedding pattern of a bare cylinder, cylinder with streamlined fairings and cylinder with short-tail fairing for various flow conditions. The hydrodynamic coefficients (e.g., lift coefficients, drag coefficients), and Strouhal number are key parameters that govern the vortex-induced vibration (VIV) on the cylindrical members. Therefore, the study would also entail investigations on hydrodynamic lift and drag forces/coefficients. The range of Reynolds Numbers covered in the studies will be 1*103 < Re < 50*103. The study examines the influence of streamlined fairing and short-tail fairing in altering the vortex shedding behavior. The outcomes based on the study would help to understand the reduction in vortex shedding due to use of streamlined fairings in place of a fixed cylinder. This in turn would help in better design of offshore structures avoiding impacts due to VIV.
Flow-Induced Vibration of Flexible Hydrofoil in Cavitating Turbulent Flow
Authors: Cheng Zhi , Jaiman Rajeev
Published: August 2024

The flow-induced vibration and cavitation dynamics of three-dimensional flow past a cantilever flexible hydrofoil are investigated using a large eddy simulation (LES) model, a homogeneous mixture cavitation model and the structural modes superposition method. The present work aims to explore a potential mechanism responsible for a propeller singing behavior, and thus focuses on the synchronized hydroelastic coupling among the pressure pulsation inside the flow field, the cavitation generation and the structural vibration. To begin, we validate the tip vortex dynamics of a flexible hydrofoil against the available experimental. Our results demonstrate that the tip vortex shedding and the blade vibration are responsible for the intense peak in the low-frequency tonal components of the noise source, and the trailing-edge vortex shedding induces broadband components. Additionally, the generation of sheet cavitation induces considerable synchronized hydrofoil vibration (subjected to a flutter-like response), and affects the pressure fluctuations in the flow field, which further dominate the features of the underwater noise sources. It is suggested that the cavitation behavior and structural vibrations co-dominate the characteristics of singing noise from a propeller blade.
Hydrodynamic Response of Semi-Submersible Platform of Floating Offshore Wind Turbine Under Extreme Waves
Authors: Cui Ting , He Guanghua , Wang Widar Weizhi , Yuan Lihao , Bihs Hans
Published: August 2024

Offshore wind turbine play a key role in the renewable energy strategy due to the advantage like the faster wind speed in offshore area and higher power generation reliability. As the development of offshore wind turbine (OWT) from near coastal area to the deep sea, floating type foundation is the inevitable direction for OWT. The hydrodynamic performance analysis of floating offshore wind turbine (FOWT) is required under different marine conditions to improve the structure safety and stability and ensure the power generation efficiency. However, the study of extreme wave condition interaction with FOWT, like tsunami waves, incidental rogue wave etc., remains a difficult scientific research challenge. In this paper, the hydrodynamic performance of Semi-submersible platform of FOWT is modeled and analyzed under extreme waves using Hydrodynamic-Coupling (HDC) method. HDC is a coupling method between the fully nonlinear potential flow (FNPF) solver and Computational fluid dynamics (CFD) solver within the open-source hydrodynamics framework REEF3D. This method satisfied the computational efficiency and high fidelity of the simulation of extreme wave events by using FNPF to provide far-field wave generation and propagation information and adopting CFD to calculate the near fluid field physical characteristics and impact details required when modeling the process of extreme state. The dynamic responses including surge and heave motion of a semi-submersible under extreme wave are carried out under typical extreme wave conditions. The numerical model is validated against experiments of rogue waves interaction with a semi-submersible platform. The HDC method achieved a computational efficiency of the same wave condition.
Experimental Study on the Wave Run-Up Properties and Slamming Loads of a Four-Column Floating Wind Turbine System
Authors: Zhou Yan , Deng Shi , Zhong Wenjun , Wang Jingkai , Fu Shenglei
Published: August 2024

China Offshore Oil Engineering Cooperation (COOEC) has constructed a semisubmersible floating wind turbine system in South China Sea. It is designed to withstand extreme sea state, horizon cyclone with a return period in 50 years. In addition to conventional design criteria, maximum inclination and acceleration, wave run-up and slamming loads also challenge the safety operation and integrity of the structure. A scaling mode test was conducted for these nonlinear-hydrodynamic domain issues. Wave run-up phenomenon is categorized into three groups based on the test observation, namely, climb-up, white water and green water. The climb-up is accepted in design due to its low load level and water entry. The white water could be tolerated if the structure withstands slamming loads, while the green water must be prevented due to its unexpected large loads. For the evaluation of slamming loads, a numerical method is proposed based on calibration result. The wave surface elevation near the platform is calibrated using the test result, and then the water particle velocity is determined by partial differentiation of the free surface boundary condition. The slamming pressure is consequently obtained using conventional formulas and empirical coefficients. The proposed wave run-up design procedure and slamming loads calculation method provide a basic reference for floating wind turbine design allowing for a smaller margin compared to widely accepted methods used in offshore oil and gas projects.
Numerical Calculation Method for Vibration and Sound Radiation of a Flat Plate Under Turbulent Boundary Layer Excitation
Authors: Huang Zhangkai , Dong Wenkai , Chen Meixia , Wang Ting
Published: August 2024

Structural vibration and noise excited by turbulent boundary layer are the main noise sources for underwater vehicles. The vibration and noise of flow-excited structures are usually solved by analytical and numerical methods, and the numerical method is widely studied because of its applicability to complex structures. In this paper, the analytical and numerical methods are analyzed for the vibration response of finite and infinite plate excited by turbulent boundary layer. Aiming at the deviation of the numerical method, a correction formulation for the numerical results is proposed from the discrete point of view of the numerical method. The results show that the numerical results after correction match well with the analytical results. The effects of different parameters on the correction are investigated, and the difference in the correction in different fluid media is analyzed. The correction formulation still works effectively for structures in water. This study provides valuable insights for the rapid prediction of structural vibration and noise excited by turbulent boundary layer.
A Statistical Probability Model for Underwater Object Detection From Sonar Images
Authors: Song Lifei , Tan Yan Zhi , Goh Eng Wei , Ang Marcelo H.
Published: August 2024

Detection of underwater structures using a multi-beam forward looking sonar poses significant challenges due to various factors such as sonar noise and multi-path acoustic reflections. In this context, machine learning techniques have proven to be valuable tools. However, they require a substantial dataset of real sonar samples to effectively train the network for structural object detection from sonar images. Notably, even untrained structures or structures that closely resemble one another may fail to be correctly detected by the network. To address this, we propose an innovative algorithm that combines computer vision and statistical probability models for the detection of underwater structures. Our proposed algorithm begins by employing OTSU and connected component labeling and analysis to identify potential regions of interest within individual single-frame sonar images. It then takes advantage of the spatial continuity present across multiple consecutive frames to pinpoint key structural areas in each frame. A probability model based on the Kalman filter is applied to precisely delineate the contours of the structure within each frame. The objective of this process is to reliably generate the edges of underwater structures from sonar images. The effectiveness and reliability of this algorithm are demonstrated through rigorous real-world sea trials conducted at a pier, further emphasizing its practical applicability and suitability for addressing the complexities of underwater structural detection.
Numerical Investigation on the Hydrodynamic Characteristics in the Tank of Aquaculture Vessel
Authors: Sun Zhiyong , Li Hui , Miao Heyun
Published: August 2024

At present, deep-sea aquaculture faces numerous challenges, encompassing issues such as water body eutrophication, fish lice diseases, and adverse sea conditions that cause damage to aquaculture equipment. In response to these challenges, a mobile aquaculture vessel equipped with recirculating aquaculture systems has emerged as a preferred solution. These systems demonstrate precise water control capabilities, ensuring optimal aquaculture water quality and mitigating the occurrence of fish diseases. In contrast to deep-sea aquaculture cages, the hull structure of aquaculture vessels exhibits superior resilience to extreme sea conditions, thereby ensuring the safety of aquaculture operations. The hydrodynamic characteristics of aquaculture tanks play a pivotal role in the growth and health of fish. The aquaculture vessel, representing an emerging innovation, currently lacks a robust foundation of hydrodynamic knowledge to effectively support aquaculture production. In this paper hydrodynamic characteristics of aquaculture tanks are investigated based on the computational fluid dynamics (CFD) method, focusing on param such as flow velocity, vortices, and flow field uniformity. The analysis reveals the existence of low flow velocity zones and dead zones in the near-corner wall region of the octagonal aquaculture tank. In the region above water depth = −3 m, a noticeable velocity gradient and lower uniformity are observed. Notably, an increase in inlet flow velocity results in an improvement in the flow field uniformity in this region.
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

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

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

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

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

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

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

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

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

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

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

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

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

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.
A Design by Optimisation Approach for Hybrid Propulsion Systems Sizing Using Actual Sailing Profiles
Authors: Vasilikis Nikolaos I. , Geertsma Rinze , Oneto Luca , Coraddu Andrea
Published: August 2024

Hybrid propulsion is considered a promising alternative to diesel mechanical propulsion which can assist the maritime industry to mitigate its contribution to climate change. The energy performance of new designs for most ship types is evaluated with the regulated Energy Efficiency Design Index (EEDI), though its limited consideration of one design point in calm water conditions and installed rated power is characterised as insufficient or even dangerous by many authors. Nevertheless, individual sailing conditions are expected to influence the resulting carbon footprint. The automotive and aviation industries have already adopted the energy assessment of new designs over operating cycles such as the Worldwide harmonized Light-duty vehicles Test Cycle (WLTC) or the Landing and Take-Off cycle (LTO). This paper demonstrates a new approach for the resizing of the hybrid propulsion system of an ocean patrol vessel of the Royal Netherlands Navy. It utilizes the actual sailing profile of a vessel based on logged high frequency operational-data. Carbon intensity is predicted by a state of the art digital twin of the vessel’s energy system developed by the authors in a previous stage. Results suggest that calm water conditions can potentially overestimate carbon intensity improvements and point to different optimal designs thus actual profiles must be used in future analyses.
Research on the Future Development of Lock Ship Type in the Three Gorges Main Line of Yangtze River
Authors: Xu Haoran , Wang Hao , Zhang Yanbing , Wang Lizheng
Published: August 2024

With the continuous development of the economy, the demand for waterway transportation is increasing, the Three Gorges locks as an important transportation hub on the Yangtze River, the problem of insufficient throughput capacity is highlighted, the development of the ship type to give full play to the capacity of the Three Gorges locks as well as the social benefits brought about by the Three Gorges locks has a very important significance. Based on the establishment of simulation model for ships passing through the Three Gorges locks, simulate the ship passing process, from the perspective of the ship’s own technology and economy and the main social benefits of the ship, combined with the adaptability of the lock facilities, the establishment of the main indexes of the demonstration, and the construction of the ship type demonstration of the comprehensive evaluation model, to comprehensively measure the comprehensive performance of the future ship type of the Yangtze River trunk line passing locks; in order to improve the passing capacity of the locks as one of the main objectives, put forward the future of the Three Gorges locks on the Yangtze River trunk line. With the main objective of improving the passing capacity of the locks, the future ship type scale of the Three Gorges mainline is proposed, as well as the representative ship type and lock chamber scale for the construction of the new Three Gorges corridor under different navigational conditions, and the results of the demonstration will provide guidance for the construction of the new Three Gorges locks in the future, as well as for the development of ships in the Three Gorges Hub.
Multi-Objective Optimization of Ship Passageway Layout Based on Pedestrian Transition Model
Authors: Zhao Jiutian , Wang Hao , Liang Fangyan , Xiao Tianli , Luo Liang
Published: August 2024

Along with the large-scale ship, the internal structure of the ship is more complex, the number of passengers on board increases, and the problem of large-scale personnel evacuation becomes more and more prominent. Nowadays, the research on total layout design mainly focuses on the comprehensive evaluation of total layout scheme, optimized design of local layout and layout optimization of compartments, while the research on the design and optimization of ship passageway layout is relatively less, and at the same time, the research on relevant ship passageway layout exists the problem that it only applies to the local layout of the ship or only gives a fixed form of passageway layout. In this paper, a new ship passageway layout optimization method is proposed to construct a multi-objective optimization model of ship passageway by combining with Pedestrian Transition Mode. This method can put forward or improve the design scheme of ship passageway layout in the early design stage of the ship, shorten the design cycle and improve the intelligent level of ship design. The example results show that the multi-objective optimization mathematical model for ship passageway layout proposed in this paper is feasible, and the comparison results show that our model effectively attenuates the peak crowd density and is more superior.
Safe Damping Factor for Non-Linear Cases of Subsea Equipment Installation
Authors: Salvador Lopes Filipe , Fernandes Antonio Carlos , Sena Sales Junior Joel
Published: August 2024

The vertical lowering of subsea equipment is one of the most used methods of installation. As the name suggests, it consists of vertically lowering the equipment using a crane on the installation ship. During the lowering, the cable’s length will change, leading to the vertical stiffness of the system not being constant. As the ship is subjected to environmental loads, its vertical motions will be transmitted to the equipment underwater. Therefore, different excitation’s frequency will be more critical depending on the water depth being studied.

When the excitation’s frequency is close to the natural frequency of the system, the equipment’s vertical motion is amplified, which might lead to the cable becoming slack. The slackness effect is succeeded by very high-tension values, usually known as snap loads, which can represent a serious risk to the installation.

This work shows that increasing the system’s damping is a way to reduce the tension values on the cable for a given environmental condition. Different damping factors can lead to different dynamic behaviors, which will have an impact on the tension values. It was seen that after the damping factor is sufficiently increased, the tension peaks on the cable will become almost constant, even after further increasing the damping. This value on which the tension peaks converge to a known and lesser value is what is referred to as safe damping factor on the title, as it can be used to determine the maximum tension peak expected to happen, allowing the increase of the operational window if a cable capable of withstanding this tension value is used.