bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of biochar addition on soil fauna communities—A meta‐analysis
Authors: Li Tao , Jiao Yan , Liu Tingting , Gu Hongyu , Li Zhihe , Wang Shaoqing , Liu Jianbiao
Published: August 2024

Soil fauna is an important part of global biodiversity and plays a vital role in ecosystems. The microbial communities in soil fauna can have significant impacts on soil fertility, as microbial communities play a pivotal role in soil function by supporting ecological integrity and agricultural productivity. This study assesses the effect of biochar on soil fauna and response of microbial communities. Biochar is a highly porous organic carbon material, and the impact of biochar on microbial communities in soil fauna remains unclear. To date, no quantitative or comprehensive investigation has been undertaken to examine the effects of biochar on microbial communities in soil fauna. In this paper, we aim to quantify the effects of biochar on the abundance and diversity of soil fauna communities in various environments by conducting a meta‐analysis of 24 studies and analysing 459 observations. The impact of biochar on soil fauna communities was determined by analysing the responses of soil fauna that included differences in biochar feedstock, pH and pyrolysis, application rates and application times, as well as soil fauna with different physiological characteristics (body size, presence of exoskeletons). The results showed that biochar had a neutral (non‐significant) effect on the soil fauna community, with a total mean effect size (Hedge's g) = −0.04 (CI: −0.28; −0.20). Results Data validation using Egger regression showed no publication bias. Higher pH biochar and biochar from conventional pyrolysis were beneficial to soil fauna, but not significant (QM (df = 3) = 4.07, p = .25). In addition, body size of soil animals significantly reflected different sensitivities to biochar application, with Medium‐sized animals benefiting the most from biochar addition (0.35; CI: 0.05; 0.65; n = 6; 56). Animals with (n = 11; 125) and without exoskeletons (n = 17; 308) also showed favourable and unfavourable responses to biochar addition, respectively. This study can provide basic data for the evolutionary pattern of animal communities during biochar soil amendment, as well as information for the comprehensive evaluation of the environmental and biological effects of biochar.
Boosting pro‐vitamin A content and bioaccessibility in leaves by combining engineered biosynthesis and storage pathways with high‐light treatments
Authors: Morelli Luca , Perez‐Colao Pablo , Reig‐Lopez Diego , Di Xueni , Llorente Briardo , Rodriguez‐Concepcion Manuel
Published: August 2024

Biofortification of green leafy vegetables with pro‐vitamin A carotenoids, such as β‐carotene, has remained challenging to date. Here, we combined two strategies to achieve this goal. One of them involves producing β‐carotene in the cytosol of leaf cells to avoid the negative impacts on photosynthesis derived from changing the balance of carotenoids and chlorophylls in chloroplasts. The second approach involves the conversion of chloroplasts into non‐photosynthetic, carotenoid‐overaccumulating chromoplasts in leaves agroinfiltrated or infected with constructs encoding the bacterial phytoene synthase crtB, leaving other non‐engineered leaves of the plant to sustain normal growth. A combination of these two strategies, referred to as strategy C (for cytosolic production) and strategy P (for plastid conversion mediated by crtB), resulted in a 5‐fold increase in the amount of β‐carotene in Nicotiana benthamiana leaves. Following several attempts to further improve β‐carotene leaf contents by metabolic engineering, hormone treatments and genetic screenings, it was found that promoting the proliferation of plastoglobules with increased light‐intensity treatments not only improved β‐carotene accumulation but it also resulted in a much higher bioaccessibility. The combination of strategies C and P together with a more intense light treatment increased the levels of accessible β‐carotene 30‐fold compared to controls. We further demonstrated that stimulating plastoglobule proliferation with strategy P, but also with a higher‐light treatment alone, also improved β‐carotene contents and bioaccessibility in edible lettuce (Lactuca sativa) leaves.
Sex differences in cervical disc height and neck muscle activation during manipulation of external load from helmets
Authors: Yin Nai‐Hao , Giulio Irene Di , Hodkinson Peter D. , Formenti Federico , Pollock Ross D.
Published: August 2024

Neck pain associated with helmet‐wear is an occupational health problem often observed in helicopter pilots and aircrew. Whether aircrew helmet wearing is associated with physiological and biomechanical differences between sexes is currently unknown. This study investigated neuromuscular activation patterns during different helmet‐wearing conditions. The helmet load was manipulated through a novel Helmet Balancing System (HBS) in healthy, non‐pilot male and female participants (n = 10 each, age 19–45 years) in two phases. Phase A assessed the acute effects of helmet‐wear on neck muscles activation during head movements. Phase B examined changes in muscle activity and cervical disc height after wearing a helmet for 45 min. In Phase A, muscle activity was similar between sexes in many movements, but it was higher in female participants when wearing a helmet than in males. The HBS reduced muscle activity in both sexes. In Phase B, female participants exhibited a greater level of muscular fatigue, and male participants’ cervical disc height was significantly decreased [5.7 (1.4) vs. 4.4 (1.5) mm, P < 0.001] after continuous wearing. Both sexes showed no significant change in muscle fatigue and disc height [male: 5.0 (1.3) vs. 5.2 (1.4) mm, P = 0.604] after applying HBS. These findings demonstrate sex‐specific physiological and biomechanical responses to wearing a helmet. They may indicate different postural and motor control strategies, associated with different neck pain aetiologies in male and female aircrew, the knowledge of which is important to reduce or prevent musculoskeletal injuries associated with helmet wearing.
Thermal-Hydraulic Investigation of the Delta–Nabla Channel Arrangement in a Solar Collector
Authors: Tariq Muhammad Hasnain , Cheema Taqi Ahmad , Khan Farooq , Mohib-Ur-Rehman M. , Asif Muhammad , Park Cheol Woo
Published: August 2024

A novel solar collector consisting of a delta–nabla configuration of flow channels is investigated in the present study. In the proposed design, triangular channels connected in series act as an absorber having more exposed area to the sunlight with an ability to store 21 L of water inside it that serves as a sensible energy storage to mitigate the intermittency issues. At the stage of proof of concept, the effectiveness of the novel collector design is not known. Moreover, its performance comparison with the existing solar thermal collector configurations is yet to be explored. Hence, there is a need to develop a comprehensive numerical model that can be used as a design template to predict the performance of the proposed collector configuration in a range of climatic conditions. Therefore, the present study is an attempt to investigate the thermal-hydraulic performance of the proposed collector, and transient numerical simulations are conducted. For accurate prediction, the effects of flowrate, inlet temperature, and irradiative flux on the outlet temperature are analyzed through a parametric study using the real-time data of ambient temperature and solar irradiative flux. The results of the numerical study are used to calculate the derived parameters such as Nusselt number, heat losses, and collector thermal efficiency by varying the water flowrate. The study shows that the heat transfer characteristics increase with an increase in flowrate and the collector can operate up to overall efficiencies between 29% and 62% at flowrates ranging from 0.1 to 0.8 L/min in winter. Moreover, the numerical model has predicted improved thermal performance of the proposed delta–nabla configurations when compared with a conventional solar collector design.
Investigations of Axially Compressed Tubular Structures Subjected to Lateral Indentations
Authors: Wang Xintong , Yu Zhaolong , Amdahl Jørgen
Published: August 2024

Tubular structures serve as fundamental designs in the offshore industry, indented to support dead weights and endure additional environmental loads. When such structures face potential lateral loads from events like ship collisions or falling objects, alongside working and environmental loadings, their unstable response in the post-buckling stage can lead to catastrophic consequences. It has been observed that existing compressive loads significantly degrade the energy absorption capacity of these structures. Investigations into axially compressed members subjected to lateral indentations are still necessary.

In this study, nonlinear finite element methods were employed to explore the responses of typical offshore tubular structures, including a leg of jacket platforms and a monopile of offshore wind turbines. Scaled models were built to maintain consistent diameter/thickness and length/diameter ratios as practical structure. Initial imperfections were introduced in line with offshore standards. Uniaxial compression tests, and lateral indentation tests with varying levels of pre-compression were conducted. Numerical results were compared to predictions based on design rules and previous research. The findings were summarized and discussed.
Structural Assessment of Functionally Graded Coped Beam Stiffeners Used in Offshore Topside
Authors: Chandrasekaran Srinivasan , M. Thennavan , Amirthalingam Murugaiyan
Published: August 2024

In recent years, there has been a growing interest in the utilization of functionally graded materials (FGM) for various innovative applications. Coped beams contribute to the establishment of a structured, protected, and uninterrupted environment for the installation of service mains and fire hydrants on the offshore topside. In their absence, the functionality and structural integrity of the system are compromised. Functionally graded materials (FGM) are employed in the present investigation as a means to reinforce the coped beam by acting as a stiffener. The enhancement of the mechanical properties of constituent materials, specifically Stellite-6 and Carbon Manganese steel, is achieved by functional grading to cater to structural engineering applications. This research investigates the microstructure evaluation and mechanical properties of FGM (Functionally Graded Material), namely Stellite-6 and Carbon Manganese steel, produced using wire arc additive manufacturing (WAAM) technique. The assessment of alloy grain structure, precipitated phases, and improved mechanical properties is conducted by the utilization of scanning electron microscopy (SEM) examination. The utilization of FGM material is expected to be widespread in offshore topside, heavy industries, particularly in situations where coped beams are necessary to fit the service mains.
Development and Tuning of a Linear Model Predictive Controller for Floating Offshore Wind Turbines to Tackle Platform Pitch Instability and Load Alleviation
Authors: Pérez Moreno Carlos
Published: August 2024

The operation of Floating Offshore Wind Turbines (FOWT) poses several challenges due to the added dynamics of the floating platform. Amongst them, the appearance of the platform pitch instability at above rated wind speeds limits the traditional PI controllers’ bandwidth. Therefore, several solutions have been proposed, including controller detuning or parallel compensation. This work explores the application of a linear Model Predictive Controller (MPC) at high wind speeds to limit the platform pitch motions and the loads. The MPC is compared to a gain-scheduled Proportional – Integral (PI) controller with parallel compensation. The linear MPC uses a fairly simple model with 3 independent Degrees of Freedom (DOF), namely platform pitch and surge, and rotor speed which allows for a thorough study on the tuning procedure. On the other hand, using a simple model limits the performance improvements close to rated wind speed due to inherent aerodynamic non-linearities. The controller objectives are explicitly stated as tracking the rotor speed and minimizing the platform pitch velocity, while a penalty to the demanded blade pitch rate is imposed. Turbulent time-domain simulations are used to generate Pareto fronts where objective function weights are swept to find optimal tradeoffs. The mean-wind speed, and turbulence intensity are found to impact the tuning procedure, and thus a set of weights is provided per wind speed. These optimal weights per wind speed are used to perform a load analysis. Great improvements in electrical power output, platform motion minimization, and shaft torsion and tower base load alleviations are achieved.
Develop AI-Aid Drilling Environment via Micro Service Systems
Authors: Sahebi Hamed , Sui Dan
Published: August 2024

The growing need for effective and precise guidance and decision-making in the ever-changing field of modern drilling operations has resulted in the incorporation of Artificial Intelligence (AI) methods into drilling systems. This paper presents a comprehensive software architecture designed to facilitate realtime drilling operations (performance monitoring and prediction) using AI technologies. In this study, an AI-aid drilling software environment has been developed via micro-service systems. Micro-service architecture plays a crucial role in real-time operations by providing a flexible and scalable framework to manage various AI components and services. It allows for the modularization of AI algorithms and data processing tasks, enabling easy integration of new AI models and technologies as they evolve. Moreover, micro-services facilitate real-time data exchange and communication between different AI modules, ensuring smooth coordination and collaboration among them, ultimately improving overall performance and adaptability.

The proposed architecture harnesses the power of AI algorithms to manage and interpret real-time data streams measured during drilling operations instantaneously. By leveraging data-driven technologies, the architecture empowers drilling engineers to make informed decisions promptly, enhancing operational efficiency and minimizing downtime. The paper outlines its key components, including data acquisition, storage, pre-processing, feature engineering, integration of AI models, and the critical stages of result visualization and validation. Notably, the architecture underscores its adaptability and scalability, emphasizing its ability to a wide range of drilling scenarios and accommodate various AI methodologies. The effectiveness of the proposed software architecture is demonstrated through two drilling scenarios, showcasing its ability to enhance accurate predictions and improve overall drilling efficiency. By presenting a holistic approach to integrating AI into drilling operations, our work contributes to the advancement of intelligent drilling systems and shows the transformative potential of AI in the energy sector.
Plug and Abandonment of Oil and Gas Wells: Experimental Study of Suspension Fluid Placements in a Confined Geometry With Insights Into the Dump Bailing Method
Authors: Faramarzi Mohsen , Akbari Soheil , Hassanzadeh Hossein , Hafezi Mohammad , Taghavi Seyed Mohammad
Published: August 2024

Plug and abandonment (P&A) of oil and gas wells is a promising technique for mitigating greenhouse gas emissions, groundwater contamination, and ecological damage caused by reservoir fluid leakages from wells at the end of their lifespan. In this operation, precise cement plug placement is crucial at specific intervals within the wellbore to achieve highest cement placement efficiency, while minimizing mixing between the wellbore fluid and cement. Several techniques are used for cement plug placement, among which the dump-bailing method stands out as a ringless, fast, and cost-effective approach widely used worldwide. This method involves the injection of cement slurry from a bailer and allowing it to settle on top of a permanent bridge plug. Fluid flow dynamics during this process is governed by several critical parameters, including the properties of the in-situ and injected fluids, geometric parameters, and operational conditions. In this study, we examine injection of heavy suspension fluid (representative of cement slurry) into a near-vertical closed-end pipe filled with a light Newtonian fluid (representative of wellbore fluid) through a scaled-down experimental setup. We focus on the impact of the suspension injection rate on placement efficiency. By utilizing high-speed camera imaging, detailed flow dynamics is captured. Our experimental results indicate that an increasing injection rate improves suspension placement within the pipe. The findings of this study can help us better understand the fluid dynamics involved in cementing processes using the dump-bailing method, as well as the importance of injection rate as a primary operational parameter when cement slurry is considered as a suspension.
Axial Cyclic Behavior of Unbonded Flexible Riser Under Cyclic Axial Loads
Authors: Liu Qingsheng , Qu Zhongyuan , Liu Xiaoya , He Jiawei , Wang Gang
Published: August 2024

Unbonded flexible risers consist of several helical and cylindrical layers, which can undergo large bending deformation and can be installed to different configurations to adapt harsh marine environment, thus can be applied to transport oil and gas resources from Ultra Deep Waters (UDW). The special construction of the structure results the complicated cross-sectional properties and has always been the research hotspot in the field of ocean engineering, and the structural behavior under long-term marine loads is the research challenges. In this paper, different from the previous studies on the cross-sectional mechanical properties of unbonded flexible riser, the cyclic tensile and compressive behavior is studied. Considering the deformation characteristics of each layer in unbonded flexible riser model and the contact deformation between adjacent layers, a theoretical method is established, and a corresponding numerical method in consideration of the detailed geometric properties of unbonded flexible riser is built up for verification. Firstly, based on a typical 2.5-inches 8-layer unbonded flexible riser model and taking the deformation characteristics of helical layer and cylindrical layer under axisymmetric loading into account, the balance equation of each layer considering the axial, radial, circumferential strains and torsional angle is established by functional principle, and the corresponding geometric relationship between adjacent layers is also included to build up the overall theoretical model of unbonded flexible riser. Then the corresponding numerical model containing all the geometric properties of unbonded flexible riser is modeled within Abaqus software and the ratio of kinetic energy to internal energy is very small to ensure the calculation accuracy. After verified through experimental results, the behavior of unbonded flexible riser under cyclic axial tension and cyclic axial compression is analyzed by the proposed theoretical and numerical methods. The theoretical and numerical results are in good agreement and the results show that: unbonded flexible riser model presents some hysteresis characteristics under cyclic axial forces and the axial tensile and compressive stiffness varies within a certain range, albeit insignificantly. Besides, the external pressure would enhance the axial stiffness of unbonded flexible riser, especially for the axial compression, where the axial compressive stiffness has significant strengthening.
Bucking Reliability Assessment of Offshore Fluid Tanks Subjected to External Pressure With Active Learning Kriging Approaches
Authors: Ren Chao , Eriksen Frank , Gundersen Stian , Xing Yihan
Published: August 2024

Offshore fluid tanks are critical components of offshore oil and gas infrastructure and are often subjected to external pressures that may lead to catastrophic buckling failure. Reliable assessment of their structural integrity is paramount to ensure offshore operations’ safety and environmental sustainability. Traditionally, reliability assessment relies on deterministic methods or experienced formulas, which may not accurately capture uncertainties from the structural and environmental parameters. Furthermore, classical probabilistic methods for reliability assessment also have their limitations. Approximation approaches like the first-order reliability method (FORM) rely on the linearity of the problems. Sampling-based approaches for the reliability assessment, e.g., Monte Carlo simulation (MCS), require many simulations/experiments, which is unrealistic for the real engineer design and optimization process. To address this problem, this study leverages advanced machine learning techniques, named active learning reliability methods, for buckling reliability assessments of offshore fluid tanks under external pressure. One Automatic Tank Cleaning (ATC) container machine from Dynamic Well Solutions AS company is used for the reliability assessment case study. The linear buckling analysis of the ATC tank is performed using finite element methods. The uncertainties encompassing geometric characteristics, material properties, and external loads are considered for the reliability assessment. One typical active learning reliability approach, AK-MCS with U learning function, is applied to estimate the probability of failure considering different minimum buckling factor requirements. The results demonstrate that the active learning reliability approach can significantly reduce the computational cost for the buckling reliability assessment. It enables an accurate and probabilistic assessment of the buckling reliability. Applying active learning reliability techniques could facilitate structural design optimization considering uncertainties.
Hydrodynamic Analysis of Different Configurations of the M4 Wave Energy Converter System Using OREGEN
Authors: Li Gangqiang , Stansby Peter
Published: August 2024

In this paper, the developed frequency domain hydrodynamic response prediction program OREGEN-BEM based on the boundary element method (BEM) with the OpenMP algorithm is applied to analyze the dynamic response of various M4 wave energy converter (WEC) systems with kinematic and mechanical constraints. The algebraic equations corresponding to the clamped connection between body-to-body due to the rigid beam and revolution joint connections are analytically derived, and they are coupled with the system equation through the Lagrange multiplier method. In this paper, a validation study for an array arranged in a triangle shape is conducted to compare the numerical results against the commercial software OrcaWave. The comparison results demonstrate that the results obtained by OREGEN-BEM are accurate and reliable. Then, the developed program is applied to study the dynamic response of the M4 WEC system with different configurations, such as 1-1-1, 1-2-1, 1-2-2, and 1-3-3.
IBNet: An Iceberg Semantic Segmentation Network Integrating Multiple Scales and Attention
Authors: Han Fenglei , Zhao Wangyuan , Xue Yanzhuo , Wu Yuliang , Peng Xiao , Zhang Jiawei
Published: August 2024

Fine-grained semantic segmentation of iceberg visual images obtained from low altitude is of great significance for ship navigation and ecological surveys, which can be regarded as the key technology of iceberg management. However, because of the bad weather in Polar regions and resource constraints, the similar texture of different ice images is the major challenge for iceberg identification, which may lead to false navigation for the ship controlling system. The main purpose of this paper is to generate accurate pixel-level iceberg image segmentation and prediction under poor sea ice optical vision acquisition conditions. A new feature extraction network IBNet with multi-scale features and double-layer attention mechanism is proposed for pyramid pooling module layer to realize weighted fusion. This learning-based approach considering six kinds of iceberg backgrounds in the scene of polar regions can be applied to support obstacle avoidance algorithm for Polar region navigation. By comparing PA, MIoU and other parameters with the other methods, IBNet performs obvious advantages in semantic segmentation task of icebergs in polar regions.
Numerical Investigation on Vibro-Acoustic Characteristics of a Metamaterial Plate Under the Excitation of Turbulent Boundary Layer
Authors: Dong Wenkai , Huang Zhangkai , Wang Ting , Chen Meixia
Published: August 2024

Flow-induced vibration is an important noise source for mechanical transportation equipment. In recent years, metamaterials have emerged as a novel approach to mitigate vibration and noise, garnering extensive research and recognition. However, research into the behavior and control of metamaterials under flow-induced excitation remains insufficient. To address this issue, this paper proposed a stiffened metamaterial plate to investigate its control performance for flow-induced vibration and noise. An uncorrelated wall plane wave (UWPW) technique is utilized to convert the stochastic problem into a collection of determinate loading scenarios, which are solvable via the finite element method. The effectiveness of this method has been validated by comparing the results with those obtained from conventional analytical approaches. This method allows for a comprehensive prediction of the metamaterial plates’ reaction to the turbulent boundary layer excitation. The findings reveal that within its bandgap range, the metamaterial plate is highly effective in attenuating vibration and noise. The addition of stiffeners to the plate elevates its first natural frequency, thus diminishing the overall vibration noise response. This paper serves as a reference for controlling vibrations under flow-induced excitation.
Energy Fluctuation of Floating Photovoltaic Solar Panel due to Wave-Induced Motions
Authors: Huang Luofeng
Published: August 2024

Solar photovoltaic is predicted to be the most widely used energy method in the future. However, the expansion of solar panels is currently limited by scarce land and lake spaces. To meet the world’s future clean energy target, floating solar panels are expected to be deployed on abundant ocean space, but floating solar panels on the ocean will be subject to loads and motions induced by waves. In particular, a continuous rotation can cause the solar panel surface to constantly change its sunlight intake angle, which could lead to a loss of energy. To investigate this phenomenon, a novel interdisciplinary experimental facility has been established, where a solar simulator was installed on top of a wave tank. A floating solar unit is placed in high-concentration light beams and subject to wave-induced motions. Its motions are measured and related to the power output. It was found that the average power output oscillates due to the motions, and an evident power loss was shown by the rotational motion. For all the tested wave conditions, the highest pitch amplitude of 6.7° corresponds to a significant level of 12.7% average power loss. Overall, the work presents a novel experimental approach and results that can estimate power output for floating solar projects in wave environments. The results also highlight the importance of considering wave attenuation technologies to avoid direct wave interaction with floating solar units.
Development of a Test Machine and Wear Test to Reproduce the Wear Caused by the Mooring Chain Connection of Floating Wind Turbines Sliding in Water due to the Movement of the Floating Body
Authors: Gotoh Koji , Murakami Koji , Utsunomiya Tomoaki
Published: August 2024

In order to ensure the safety of floating offshore wind turbines, it is essential to establish a method for assessing the amount of wear on the mooring chain. This allows maintenance costs to be considered at the planning stage of the installation.

In this study, an experimental system was constructed to reproduce the wear behavior of a mooring chain with dimensions similar to those of the in-service machine, when it is completely submerged in water. The wear behavior was investigated under several tension conditions, and it was confirmed that the wear behavior in a fully submerged environment was different from that in air or in liquid drops. In addition, a discussion on the mechanism of the wear progression stages of mooring chains was presented.
Radiation and Scattering of Water Waves by a Submerged Elliptic Disc
Authors: Gayen Rupanwita , Farina Leandro , Hoque Ajijul , Datta Ranadev
Published: August 2024

In the present paper, the radiation and scattering by an elliptic disc submerged in infinite-depth water are investigated. The problems are solved by reducing them to two-dimensional hyper-singular integral equations over the surface of the disc. A spectral method is used to solve the integral equation numerically. Numerical results are presented for different hydrodynamic quantities related to scattering and radiation by the disc. Initially, the formulation is validated against published results for a circular disc. Once it is found satisfactory, a rigorous parametric study is conducted for the elliptic disc. The primary focus of the presented study is to investigate the dependence of several physical quantities such as added mass, damping coefficient, and exciting forces on the depth and geometry of the disc. From the results, it is observed that when the body is near the free surface, the pressure field around the body changes abruptly and resonance occurs. Also, by solving the radiation problem, it is seen that for the elongated body, that is, where the ratio of the semi-major axis to the semi-minor axis is high, added mass and damping coefficient change significantly. The present study may be useful as a benchmark study. Also, in the domain of ocean energy, this study can give a rough idea about the design of an oscillator. At present, bases of all the oscillators are modelled as circular. This study reveals that an elliptic base might be useful as well.
Analysis of Fracture Parameters for Compact-Tension-Shear Specimen of Orthotropic Materials
Authors: Jin Pengfei , Liu Zheng , Chen Xu , Wang Xin
Published: August 2024

Treating orthotropic materials as isotropic for strength analysis and design can introduce significant errors, resulting in considerable safety risks. Furthermore, in practical conditions, cracks often exhibit mixed-mode fracture behavior, and the combination of orthotropy mechanics gives rise to an even more complex stress field in the vicinity. In this context, performing Compact-Tension-Shear (CTS) tests is a promising research methodology to determine fracture toughness of orthotropic materials in mixed mode I&II. Therefore, this study conducted a comprehensive two-dimensional finite element analysis (2D FEA) on orthotropic CTS specimens to assess critical parameters in fracture toughness including stress intensity factors (SIF) and crack mouth opening displacement (CMOD) compliance. The analysis matrix encompassed a wide range of material orthotropy, crack length ratios, and loading angles. Results showed that the impact of orthotropy varies under different geometries and loading angles, while different fracture parameters exhibit varying degrees of sensitivity to orthotropy. The obtained results would contribute to the development of fracture toughness testing methods for orthotropic materials under mixed-mode loading and provide a reference for standardization in the process.
Hydroelastic Analysis of Floating Photovoltaic Floater Under Regular Waves
Authors: Leventopoulou Theano , Dai Jian , Jiang Zhiyu
Published: August 2024

The need for renewable energy is increasing and limited land space for installations has led to the rise of floating photovoltaic (FPV) systems, a promising and relatively new technology for harnessing solar power on water surfaces. Apart from the design and the construction of the FPVs, the hydroelastic problem posed by water waves on plate-like floating structures has a considerable value in the offshore application. This study focuses on the frequency-domain hydroelastic analysis of a recently proposed FPV concept with rope connection. In numerical modelling, each FPV float is simplified as a rectangular plate and modelled by using Mindlin plate elements considering only the vertical degrees of freedom. After a mesh convergence study, the FPV systems with one float and two interconnected floats are studied. Through parametric studies considering different wave headings, periods, and connector stiffness, we compare the distributions of displacement, and bending moments along the float for each system. This study serves as a reference for understanding the hydroelasticity effect of simple FPV systems under different environmental conditions and mechanical connections.
Cross Sectional Mechanical Characteristics and Sensitivity Analysis of Unbonded Flexible Risers Under Torsional Loads
Authors: Ma Weilin , Zhang Xiansheng , Yang Yongchun , Chen Changlong
Published: August 2024

Unbonded flexible risers have complex structures and numerous structural parameters. The torsional loads carried by each structural layer lead to different levels of coupling deformations of layers. These deformations bring challenges to the structural design and mechanical characteristics analysis of flexible risers. This study establishes the theoretical model of flexible risers under the torsional loads according to the law of conservation of energy and the deformation geometry theory. Depending on the material properties and structural forms of each layer, this study divides the layers of flexible risers into three categories: cylindrical layer, metal spiral layer and polymer spiral layer, and derives the expressions of torsional loads and torsional stiffness. The calculation program in this study is compiled with MATLAB software to calculate the mechanical properties of flexible risers under clockwise and counterclockwise torsional loads. This study analyzes the influence of structural parameters on the torsional performance of flexible risers. Calculation and analysis of the influence of structural parameters on their mechanical properties can provide not only the further insight into the mechanical principles of each structural layer, but also the reference for structural design and optimization of flexible risers.
Piloting of Vessel Technical Index
Authors: Guo Bingjie , Tvete Hans Anton , Vartdal Bjørn Johan , Wang Shuai
Published: August 2024

Studies have shown that about half of the reduction potential can be achieved through adopting the fuel saving measures. However, the lack of information, uncertainty about hidden costs/benefits, information asymmetry between stakeholders, conflicts of interest and split incentives etc. hinder the application of the fuel saving measures. To evaluate ship technical performance and efficiency of fuel saving measures in a transparent way is critical to remove the barriers. Thus, DNV has proposed Vessel Technical Index (VTI), which isolates the technical condition of in-service ship, by accounting and adjusting for the relevant operational factors and weather effects. This index can evaluate ship technical performance in an effective and transparent way, which can enhance the cooperation between stakeholders to remove barriers that hinder the application of fuel saving measures, which also can help ship owners to optimize ship maintenance. VTI index is based on some measurement parameters, which need to be collected, processed, and synchronized. The measurement data always includes noises, and the physical models to correct the operational factors and weather effects also have model uncertainty. Thus, a systematical method to collect data, process data, calculate VTI index and evaluate VTI uncertainty has been developed, which will be presented in this paper. Three use cases of the VTI index will also be discussed.
A Modeling Method of Predicting Service Life at Crack Threshold Stage for Tensile Armor of Flexible Pipes Under SCC-CO2 Environment
Authors: Ye Wenye , Yang Qi , Ribeiro Marcelo , Ribeiro Carlos , Zhu Linfa , Alvino Alberto , Roberts Andrew , Tan Zhimin
Published: August 2024

Cracks triggered by Carbon Dioxide initiated Stress Corrosion Cracking (SCC-CO2) have been identified as a new failure mode in flexible pipes, yet a method of predicting its occurrence, especially the stage of crack initiation (T1) is lacked in the industry. The root cause of SCC cracks is complex, the experiment observation shows the cracking may initiate from different locations and grow along different paths. As a starting point, this paper introduces a methodology of T1 prediction on the basis of equivalent initial flaw size (EIFS) theory and also back-extension of Paris linear section. It implies the condition that SCC-CO2 cracks initiate from corrosion pits and propagate through grain boundaries. The influential factor from environment mainly includes the stress utilization factor (UF), CO2 fugacity and operational temperature. After the preliminary calibration using data from dissected pipes retrieved from different oil fields, the model is able to predict typical trends, agreeing with the most field observations. Investigation continues to understand the mechanisms leading to some specific deviations, and to explore potential solutions and improvements. The presented approach is anticipated to provide a reliable and consistent prediction of nucleation duration in determining SCC-CO2 service life. Furthermore, the model in this methodology will be further calibrated and validated against future tests and field experiences.
Numerical Study on the Fluid Interactions and Gap Resonance Between Two Adjacent Floating Bodies
Authors: Huang Lin , Yu Liwei , Wang Shuqing
Published: August 2024

The analyses of fluid interactions between multiple floating bodies have been of practical importance in the field of ocean engineering, such as float-over installation, offshore side-by-side operation and floating solar photovoltaic (FPV) system with array of adjacent floating bodies. Waves dominated by the diffraction potential show substantial wave surface elevation at gaps in multiple floating bodies, so there is an urgent need for an in-depth mechanistic study of this problem.

In this study, a side-by-side operation ship model of two ships with identical main scales is taken as the research object, and the potential flow theory is taken as the basic framework to establish the three-dimensional boundary element method based on the free surface Green’s function which is applicable to the analysis of wave interaction response. The self-developed floating body hydrodynamic calculation program is used to simulate the wave surface at the gap of the two-ship model under different frequency waves.

It was found that at high frequencies, a large increase in the wave surface occurs in the gap of multiple floating bodies, and that the wave surface rise is mainly caused by diffraction waves.
Effects of Needle Peening on Fatigue Strength of Aluminum Alloy Welded Joint Containing a Surface Defect
Authors: Fueki Ryutaro
Published: August 2024

This study investigates the impact of needle peening (NP) on the fatigue strength of aluminum alloy welded joints with an artificial semicircular slit at the weld toe. Uniaxial fatigue tests were performed on specimens, both with and without a slit, at a stress ratio of 0.05. The fatigue strength at 2 million cycles increased by 11%–100% due to NP treatment. Notably, specimens with 1.0 mm slit depths demonstrated fatigue strengths equivalent to those without a slit, attributed to the introduction of substantial deep compressive residual stresses. This finding suggests that NP can effectively mitigate semicircular slits less than 1.0 mm, enhancing the reliability of aluminum alloy welded joints. Such slits, typically challenging to detect via standard nondestructive inspections, can be addressed efficiently through NP.
Numerical Calculation and Analysis of Motion Response of Moonpool Floating Wind Turbine
Authors: Li Mingxuan , Chen Junxuan , Zhang Xinshu
Published: August 2024

The motion response of a floating wind turbine is tightly controlled by rigorous requirements, as overly vigorous movements may lead to damage of the turbine equipment. Consequently, mitigating the motion response of the wind turbine is of paramount importance. The moonpool, defined as an opening vertically aligned with the sea surface, penetrating the platform and connected to the sea, can afford a relatively stable operating environment for internal operations. In this study, the SESAM software developed by DNV-GL is applied to utilize numerical simulation to conduct frequency-domain analysis of the hydrodynamic performance of a barge-style floating wind turbine with a moonpool under both survival and operating conditions. The research focuses on investigating the motion response characteristics of the wind turbine platform. The parameters of the barge-style floating wind turbine are referenced from [1]. The obtained resonant frequencies of various orders of the moonpool are compared with experimental results, validating the reliability of the calculations. Additional comparisons are made regarding platform added mass, radiation damping, and six-degree-of-freedom motion response, identifying abrupt changes in the turbine’s motion performance near resonance frequencies. Furthermore, adhering to DNV standards, the study evaluates the safety of the wind turbine platform under two design conditions based on maximum tilt angle and maximum acceleration of the nacelle position. Finally, a parametric analysis of the platform is conducted. Using platform length, moonpool length, and platform molded depth as independent variables, different principal dimensions of the wind turbine platform are estimated based on scale ratios. Subsequently, an analysis of the turbine’s motion response and safety under various main dimensions is performed. The present study indicates that enhancing the safety of a floating wind turbine can be achieved by increasing the platform length and reducing the platform molded depth appropriately. Additionally, enlarging the dimensions of a rectangular moonpool appropriately contributes to further enhancing the safety of platform under harsh sea conditions.
Predicting the Sliding and Penetrating Resistances of a Mobile Subsea Mudmat Accounting for Maintained Load, Shearing and Reconsolidation
Authors: Liu Kehan , Wang Dong , Fu Dengfeng
Published: August 2024

Subsea mudmats are employed extensively as a shallow foundation on soft clay to support the seabed structures for offshore oil and gas developments. Compared with a conventional fixed mat, an emerging concept of the tolerably mobile mudmat, which is to allow foundations sliding with the pipeline supported to accommodate the periodic thermal expansion and contraction, is a potential solution to reduce the foundation sizes and then the installation cost. In this paper, the performance of a tolerably mobile subsea mudmat subjected to maintained load and periodic sliding events with intervening consolidation during its whole life is investigated. A series of coupled large-deformation finite-element (LDFE) analyses were carried out. LDFE results of several typical field scenarios are used to develop an extended effective stress framework, which is capable of predicting the changes in sliding and penetrating resistances of the mobile mudmat due to maintained and cyclic loads. An extended reconsolidation solution within the framework was proposed to simulate the coupled dissipation response of excess pore pressures that remaining from partial installation consolidation and generating progressively from cyclic shearing. The proposed framework is validated by the existing centrifuge tests. Variations in stress state and strength profile are discussed to interpret the changing sliding and penetrating resistances. The LDFE and framework analyses provide insights that a shorter installation period and frequent slide events are contributed to a rapid hardening of resistance.
A Coupled CFD-FEM Study on Slamming Loads and Structural Dynamic Responses of a Simplified Ro-Ro Ship
Authors: Gao Ziyu , Yue Jingxia , Zhao Xiaosa , Zhang Chi
Published: August 2024

Roll-on/Roll-off (Ro-Ro) ships with small deadrise angles may subject to substantial hydrodynamic loads, particularly during slamming events in adverse sea conditions. While existing studies have primarily focused on slamming loads and structural dynamics in the bow flare region, a notable research gap persists in understanding these phenomena when the bow doors are open — a critical scenario during emergencies or abrupt landings.

This paper explores the specified scenario using a simplified model of a Ro-Ro ship — a symmetrical wedged grillage structure with two stiffened plates representing the bow doors. Numerical analysis based on a coupled CFD-FEM method is employed, and the slamming event is modeled as a free-fall water entry process. Validation is performed through simulations on a wedged grillage structure with a vertical bow plate and comparing results with available experimental studies. Subsequently, case studies are conducted for the simplified Ro-Ro ship with the bow doors in open and closed states, respectively, to assess the influence of the door status on slamming and structural responses. Additionally, four different current velocities are considered to investigate the effect of forward speed on slamming loads and dynamic responses of Ro-Ro ships.

The study reveals that opening bow doors results in negative slamming pressure on the bow door structure, contrasting with positive values when doors are closed. Moreover, the strains (representing structural deformation) in the connection region between the doors and the hull structure is positive in the door-open state, in contrast to the negative strain observed when the doors are closed. A peak in the time history of strain is detected only when the doors are open. The study also shows that slamming occurs more rapidly with the increase of current velocity. As the current velocity increases, the amplification of maximum strain in the connection area also increases when the bow doors are open. These findings could be useful for the design of bow doors and the operation of Ro-Ro ships.
Crack Propagation Test of Stiffened Panel in Low Temperature
Authors: Feng Guoqing , Yang Xuanyu , Li Songcheng , Li Kaiyan
Published: August 2024

With the increasing exploration of polar regions, the problem of fatigue crack propagation during ice-breaking operations of ships in polar low-temperature environments has received more and more attention, which has put forward higher requirements on the mechanical properties of high-strength steels used in hulls in low-temperature environments and the fatigue crack propagation properties of typical details of hulls in low-temperature environments. In this context, the study of fatigue crack propagation of typical details of hulls in low-temperature environment is caried out. The main contents of this paper are as follows:

The Test specimens with a through-thickness initial crack are designed based on the bow stiffened plate structure of the hull, and fatigue crack propagation tests of the bow stiffened plate structure in a low-temperature environment are conducted. It was found that with the gradual propagation of the fatigue crack, the fatigue crack propagation rate gradually increased and the fatigue crack tip gradually expanded in the direction away from the inter-reinforcement welds. Then, the finite element simulation of fatigue crack propagation test of stiffened panel of hull under low temperature environment is carried out, and the accuracy of the simulation results is verified by comparing the simulation results with the test results.