bluuebunny/crossref_metadata_2025_split huggingface dataset:
Model Tests of a 12 by 18 Floating Solar Array Under Regular Wave Conditions
Authors: Jiang Zhiyu , Dai Jian , Saettone Simone , Souto-Iglesias Antonio 
Published: August 2024

Abstract
Floating solar has appeared as an emerging technology in the global renewable energy portfolio. Although several floating solar concepts have been proposed in the past, most of them are well-suited for deployment in inland or near-shore water bodies with benign environmental conditions. To address the need for sustainable and cost-effective floating solar energy production in offshore areas, a novel modular floating photovoltaic concept suitable for offshore environmental conditions has very recently been proposed in (Jiang et al. 2023). The concept proposes the use of semi-submersible floats for individual modules and crisscrossed rope connections to join neighbouring modules. Based on the conceptual design, this paper presents the experimental investigation of a 12 by 18 array with 216 floats in regular waves under both operational and survival conditions. First, we describe the model test set-up, the physical models of the simplified floats, the environmental conditions, and the sensor instrumentation and measurement. Then, selected time histories of the array motions are analysed. It is observed that the tested large array has good motion performance with limited wave overtopping. Finally, limitations of and lessons learned from the model tests are summarised. This paper paves the way for the next-stage research and development of the floating solar concept for harsh offshore conditions.
CFD Evaluation of the Self-Starting of a Vertical-Axis Wave Turbine and the Related Flow and Load Characteristics
Authors: Yan Deguang , Yang Yingchen , Ge Zhongfu 
Published: August 2024

Abstract
The research and application of marine renewable energy have received much attention due to its potential to generate power with less emissions than traditional sources. Among various types of wave energy converters (WECs), research is still in its infancy for Vertical-Axis Wave Turbines. While the concept has been well adopted in the wind energy industry, the use of this technology for wave energy harvesting could meet challenges due to the reciprocal motion of surface waves. When previously tested, the wave turbine design showed promising spin-up and sustained rotation of the rotor in regular waves. This test encouraged detailed assessment of the self-starting process of the rotor in the present work.
For numerical simulation, a Computational Fluid Dynamics (CFD) model following the Reynolds-Averaged Navier-Stokes framework was established. The model took various aspects into account, such as the influence of the numerical waves, the highly unsteady initial self-starting process, and the appropriate gridding strategy needed to suit a wide range of rotational speeds from near-zero to the quasi-steady, terminal speed of the rotor. The CFD model was applied to reveal detailed characteristics of the flow field and to evaluate the sensitivity of the self-starting process to different inertial properties and damping coefficients of the rotor. The simulation showed that the inertial properties of the rotor would only affect the efficiency of the self-starting process. In contrast, the damping coefficient could have a profound effect on the attained steady-state rotational speed, which has strong implication for the design of power-take-off.
The methodology established in the present work will be invaluable for design optimization as the self-starting process is an important stage of the device operating in an ever-changing environment. The methodology is also transferrable to other types of renewable energy devices that are equipped with a self-started rotor.
Role of Front Splitter Plate Gap on the Flow-Induced Vibrations of a Circular Cylinder
Authors: Tandon Ishan , Kanna Rohan , Joshi Vaibhav 
Published: August 2024

Abstract
In engineering applications, we frequently encounter flow around circular cylinder-type geometries, such as in cooling pipes for heat exchangers, risers and pipelines in oil and gas extraction, storage silos, and buildings in civil engineering. It is widely known that unsteady flow past a bluff body causes alternate vortex shedding and subsequent fluctuating lift and drag forces, resulting in structural damage. It becomes increasingly important to suppress these oscillations to prevent shortening the structure’s lifespan. Amongst various passive suppression devices studied previously, the addition of rigid splitter plates along the horizontal centre-line of the cylinder both upstream and downstream has been found to be quite effective in mitigating transverse vibration. This study aims to understand the previously unexplored effect of varying the upstream gap on suppressing flow-induced vibrations. To accomplish this, the optimization of the gap (g) between the cylinder of diameter D and the trailing edge of the front splitter plate in the range of 0 to 5D has been explored. A two-dimensional stabilized Petrov-Galerkin variational formulation is used to solve the Navier-Stokes equations on an arbitrary Lagrangian-Eulerian moving mesh framework to investigate the response at a low Reynolds number of 120 for reduced velocities of 3–12. The plate length is kept equal to the diameter of the cylinder, and the system is free to oscillate in the streamline and crossflow directions under a low damping ratio of 0.01 and a mass ratio of 6.9. The results of this study will provide valuable insight and aid the development of passive suppression devices for deep-sea structures.
Experimental Study on the Dynamic Responses of a Novel 10 MW Floating Offshore Wind Turbine Integrated With a Fish Cage
Authors: Zhang Sheng , Zheng Xiang Yuan , Zhang Xiangyu , Lei Yu , Liu Yue , Jiang Yucong , Qian Kehao , Li Xin 
Published: August 2024

Abstract
This experimental work is to study the dynamic responses of a novel floating offshore wind turbine integrated with a fish cage (FOWT-FC) under wave and wind loads and to provide a benchmark for the establishment of numerical simulations. A series of model tests of scale 1:30 have been carried out in the ocean basin at Tsinghua Shenzhen International Graduate School (SIGS). This paper provides a detailed description of the experimental setup, including the design, fabrication, calibration and identification of the model, type and arrangement of the sensors. The 6 degrees of freedom (DOFs) displacements of cage, the accelerations at tower top and base and other responses are collected and analyzed. The displacement response amplitude operators (RAOs) are obtained through white noise wave tests, manifesting the excellent seakeeping performance of FOWT-FC. Besides, all responses in the operational and non-operational load cases are below the code limits. A group of controlled experiments are set up to investigate the effect of wind on dynamic responses, and several findings are discovered. In general, wind loads increase low-frequency responses, but have little effect on wave-frequency responses. Moreover, the low-frequency growths under turbulent wind are more significant than those under steady wind. Besides, the turbulent wind enhances the high-frequency responses at around tower’s 1st-mode vibration frequency. Whether under the action of random waves alone or combined wave-wind, the cage’s motions are predominantly controlled by low-frequency and wave-frequency responses, while hardly influenced by high-frequency excitations. The blades’ 3P excitation is not observed in the cage motion spectra, but found in the tower acceleration spectra. Also interestingly, the tower top acceleration has more pronounced spectral contents at high frequencies than the tower base acceleration does. On the contrary, the tower base acceleration has more pronounced spectral contents at low frequencies than the tower top acceleration does. These low frequencies are sourced from the wind loads and difference-frequency hydrodynamic loads.
Free Roll Decay of FPSO and FLNG Hulls With Bilge Keels Through Experimental Tests and CFD Simulations
Authors: Kim Joo-Sung , Choi Yong-Ho , Han Solyoung , Yuck Raehyoung 
Published: August 2024

Abstract
The objective of present paper is to assess the roll damping characteristics of FLNGs and FPSOs. The roll damping characteristics are examined through the three prediction methods; 1) Ikeda’s empirical method, 2) experimental tests and 3) CFD simulations. Practically, design variables that can be adjusted to reduce the roll motion include only the bilge radius and the height of bilge keel. In the present paper, a parametric study has been made considering various combinations of bilge radius and bilge keel height.
The three prediction methods constantly show that the roll damping of FLNG and FPSO hulls considered in the present paper increases with increasing bilge keel height and decreasing bilge radius. Using experimental and simulation data with systematic variation of bilge radius and bilge keel height, it is shown that the roll damping can be correlated with a function bbk/bbk_max0.8. Using this relationship, a design guideline is proposed to simultaneously optimize the roll damping performance, the structural integrity of bilge design and the constructability related to bilge design of the hull form of FPSOs and FLNGs.
An Autonomous Ship Formation Method Based on Virtual Physical System
Authors: Ding Ming , Wang Lei , Wang Yiting 
Published: August 2024

Abstract
The current ship autonomous formation algorithm directly or indirectly designates the specific position of each ship in the formation, which leads problems such as large communication volume, inability to formation according to the proximity principle, and difficulty in expanding the number of ships, etc.. With the expansion of formation scale, these problems will be more significant, so the research of new formation strategy is imperative. Inspired by the rules of nature and artificial potential field method, this study proposes an autonomous formation method that can automatically select the appropriate position according to the actual situation without specifying the specific position of the ship in the formation: the Virtual Wall Method, which solves the problems above. The effectiveness of this algorithm is verified by the simulation of static, dynamic, rotation, scaling and obstacle avoidance of the ship formation. The Virtual Wall Method is applicable to both first- and second-order systems and has significant advantages in large-scale formation of ships.
Diagnostic Digital Twin for Anomaly Detection in Floating Offshore Wind Energy
Authors: Stadtmann Florian , Rasheed Adil 
Published: August 2024

Abstract
The demand for condition-based and predictive maintenance is rising across industries, especially for remote, high-value, and high-risk assets. In this article, the diagnostic digital twin concept is introduced, discussed, and implemented for a floating offshore turbine. A diagnostic digital twin is a virtual representation of an asset that combines real-time data and models to monitor damage, detect anomalies, and diagnose failures, thereby enabling condition-based and predictive maintenance. By applying diagnostic digital twins to offshore assets, unexpected failures can be alleviated, but the implementation can prove challenging. Here, a diagnostic digital twin is implemented for an operational floating offshore wind turbine. The asset is monitored through measurements. Unsupervised learning methods are employed to build a normal operation model, detect anomalies, and provide a fault diagnosis. Warnings and diagnoses are sent through text messages, and a more detailed diagnosis can be accessed in a virtual reality interface. The diagnostic digital twin successfully detected an anomaly with high confidence hours before a failure occurred. The paper concludes by discussing diagnostic digital twins in the broader context of offshore engineering. The presented approach can be generalized to other offshore assets to improve maintenance and increase the lifetime, efficiency, and sustainability of offshore assets.
Characteristics of Organic Carbon Distributions in Tidal Wetland of the Yangtze River Estuary
Authors: Chen Shizhe , Lou Sha , Yang Zhongyuan , Liu Shuguang 
Published: August 2024

Abstract
Due to the coupling effects of runoff and tidal currents, the carbon cycle process of tidal wetlands in the Yangtze River estuary is extensively influenced by both hydrodynamic and environmental factors. In this study, samples of particulate organic carbon (POC) and dissolved organic carbon (DOC) in water, and total organic carbon (TOC) in surface sediments were taken at sites Sanjiagang (SJG) and Nanhui (NH) along the Yangtze River estuary (YRE) in December 2022 to investigate the tidal variation of organic carbon distributions. The results showed that the concentrations of organic carbon, including POC, DOC and TOC were higher at SJG than at NH. According to the Pearson correlation analysis, the concentrations of POC and TOC were positively correlated at NH, and tidal elevation had a positive effect on TOC concentrations. Organic carbon concentrations and water physicochemical properties (salinity, dissolved oxygen, temperature, turbidity and pH) had strong relevance. Results in this paper can provide a scientific basis for the assessment of regional and global carbon balance in coastal wetlands.
Numerical Modeling of Bismuth-Based Plugs for Well Plug and Abandonment
Authors: Jaculli Marcelo Anunciação , Hmadeh Lewaa , Sangesland Sigbjørn , Elahifar Behzad 
Published: August 2024

Abstract
Plugging and abandonment of wells is a fundamental operation within the oil and gas industry, which has gained more focus recently due to safety and environmental concerns. Downhole plugs must withstand extreme pressure and temperature conditions and, in some cases, corrosive environments. Ensuring good sealability is of utmost importance considering the long-lasting perspective of P&A. The usage of plugs made of bismuth alloys is a recent technology that has been vouched as an improvement over traditional cement solutions, especially in terms of resistance to pressure, corrosion, and leakage. Bismuth has the unique characteristic of expanding upon solidification, a phenomenon that has been the main driver for suggesting it as a potential barrier material. Furthermore, creep and aging effects become relevant since the plug is placed in temperatures that could reach close to the melting point of its alloy. This paper comprehensively assesses the necessary modeling steps for characterizing the eutectic bismuth-tin alloy appropriately in commercial finite element analysis software considering the aforementioned phenomena, including a comparison with laboratory tests. Simulations are carried out to test this plug model under different downhole scenarios. Results show that the resistance of the plug to pressure diminishes when the downhole temperature increases, although the exhibited resistances seem to suffice field applications. These conclusions are intended to support bismuth in its qualification as an accepted barrier material.
Experimental Study on the Influence of Seepage on Sediment Initiation Under Steady and Oscillatory Flows
Authors: Zhang Yuhuan , Cui Lin , Zhai Hualing , Jeng Dong-Sheng 
Published: August 2024

Abstract
Sediment incipient motion is a crucial stage in the erosion process, making it imperative to study its mechanism. Seepage can significantly alter hydrodynamic forces around soil particles near seabed surfaces and affect erosion processes. Most previous studies ignored the effect of seepage by assuming the seabed surface as impermeable. Some studies attempted to clarify the effect of seepage force on sediment initiation theoretically, but quantitative analysis through laboratory tests is necessary. In this study, an in-house designed Erosion-Seepage System (ESS) is used to simulate the erosion process with seepage under either steady or oscillatory flow. Through the designed ESS, the erosion rate and seepage can be directly determined and their relationship can be established. The experimental results show that the upward seepage reduces the initial shear stress of the sandy bed under a steady flow. Furthermore, the upward seepage under an oscillatory flow also results in a reduction of the shear stress amplitude required for the motion of the sediment as well as an increase in the erosion rate. In addition, the erosion rate becomes more pronounced for large seepage.
Design and Optimisation of Parallel Hybrid Converter Connected With LCL Filter for Offshore Wind System
Authors: Li Ning , Finney Stephen , Judge Paul D. , Zhang Yixiao , Ng Eddie Yin Kwee 
Published: August 2024

Abstract
Parallel hybrid converters utilise partially rated Silicon Carbide (SiC) Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) based converters as active filters or partial power transfer for slower switching Silicon (Si) Insulated-Gate Bipolar Transistor (IGBT) based converters. This allows the effective SiC MOSFET switching frequency of the overall converter to be significantly increased, reducing the requirement for external filters and increasing the converter’s current control bandwidth, without relying on a wholly SiC MOSFET-based approach in the same topology. In the practical network system, the transformer and capacitor are usually adopted as Inductor-Capacitor-Inductor (LCL) filters after the converter. This paper investigated the potential performance of Parallel Hybrid Converter (PHC) topology with the LCL filter and also designed the component parameters for this topology, including the IGBT and SiC impedance. The parallel direct current supply for both converters also opens up the potential for partial-load efficiency improvements. A long-horizon finite step model predictive current controller is implemented as the control system, which allows significant flexibility in the converter’s operation, compared with direct space vector control and fractional power control. The results validate that the parallel hybrid converter with an LCL filter could achieve the grid-current total harmonic distortion (THD) below 3% with IGBT bridge frequencies in 2 kHz. The stability performance in dynamic situations, including system fault and harmonic injection, is also verified.
A Modern Data-Driven Approach for Accurately Assessing Wave-Induced Loads and Responses of Ships Using AIS and Weather Data
Authors: George Jagite , Aarsnes Lars Holterud , Storhaug Gaute 
Published: August 2024

Abstract
Prescriptive load formulations used during the design process for most ships are based on a presumed design environment. For standard ships, the strength evaluation is performed according to the North Atlantic design environment, while the fatigue design may be verified according to the Worldwide environment. However, it is well-known that some ships operate globally, while others operate in specific areas, being subjected to different environmental conditions than assumed during the design phase. Therefore, the prescriptive loads from design may not be relevant for the actual operation of certain ships. Consequently, within the last decade, significant attention has been given to digital twin models and hull monitoring systems, where the hull structure utilization (e.g., strength and fatigue) is continuously assessed by combining structural models with actual encountered weather conditions. Setting up advanced digital twin models and running the analyses takes time and effort, preventing such models from being used operationally on a large scale. Aiming to reduce the risks and increase the profitability of ships, as well as to make structural health monitoring solutions more accessible, an effective innovative hull condition monitoring system is proposed by combining advanced data-driven techniques with hindcast weather data. This paper presents the novel method developed for accurately approximating the wave-induced loads and responses for all ships without complex hydrodynamic models. The solution makes accurate predictive and preventive maintenance accessible for all.
Strain Capability Analysis of Metallurgically Clad Pipe With Girth Welds Under Combined Loads
Authors: Yang Renjie , He Yangye , Zhang Yu , Duan Menglan 
Published: August 2024

Abstract
Metallurgically Clad Pipes (MCP) have a strong bond between the outer pipe and the liner, effectively avoiding the separation failure of Mechanically Lined Pipes (MLPs). The girth weld position in an MCP becomes the weakest point of the entire pipeline. In this study, a three-dimensional bimetallic model with a girth weld is established, considering factors such as weld reinforcements, weld bottom width, weld groove angle, misalignment value, heat-affected zone width, and material properties of the girth weld and heat-affected zone. The influence of different working internal pressures and bending moments on the load-bearing and strain capacity of MCP under combined loads is investigated. With the increase of working internal pressure, stress concentration and plastic deformation occur in the heat-affected zone of the metallurgical clad pipe with girth welds. The stress level at the weld location is relatively low. An appropriate working internal pressure can effectively improve the load-bearing capacity of MCP, which allows it to withstand larger bending loads. Increasing the bending moment, the stress at the girth weld and heat-affected zone significantly increases, resulting in plastic deformation and a decrease in the overall load-bearing capacity of the pipeline. Considering pipe failure, the bending moment within the combined loads assumes the most critical role. It is concluded that for the MCP under combined loads, the overall stress level is lower at the girth weld, while the heat-affected zone experiences higher stress which may become the main location of failure. The present research results can provide a theoretical basis for the design, manufacturing, and safety assessment of MCP.
Multi-Surrogate Model Aided Bow Optimization of River and Coastal Connection Ship
Authors: Zheng Long , Yan Shikuan , Chen Xinyu , Kun Ban , Chen Shunhuai 
Published: August 2024

Abstract
In the simulation-based ship design, performance evaluation plays a crucial role. However, the process of evaluating the hydrodynamic performance of a ship can be both time-consuming and expensive, especially when relying on high-fidelity computational fluid dynamics (CFD) methods. To address this issue, this paper constructs an approach to hull form optimization design based on a multi-surrogate model. The study focuses on the bow optimization of River and Coastal Connection Ship. Two classic surrogate models are utilized to compare the multi-surrogate model’s approximation capabilities in four test functions. The numerical experimental results demonstrate that the multi-surrogate model exhibits superior forecast accuracy and robustness compared to the other models. Furthermore, a simulation-based optimization design model for the resistance performance of river and coastal connection ships is established, utilizing the aforementioned surrogate model and solved through an evolutionary algorithm. The result indicates that the multi-surrogate model facilitates the attainment of improved optimization design results. The optimization of the bow shape of the river and coastal connection ship through the multi-surrogate model effectively enhances the resistance performance of the target vessel. The proposed approach offers a more efficient and cost-effective method for evaluating the hydrodynamic performance of ships and optimizing their hull forms. The use of a multi-surrogate model significantly reduces the computational cost of the optimization process, while also improving the accuracy and robustness of the results.