bluuebunny/crossref_metadata_2025_split huggingface dataset:
Challenges and Impacts of Severe Slugging Fatigue on SLWR Design
Authors: Vieira dos Santos Junior Joel , Ferreira Senra Stael , Reis Guilherme Paulo Vitor , Massae Hayashi Lucila , Pereira Resende Rodrigo , Gonçalves Moreira Dinis Marcelo , Donni de Sena Bernardo 
Published: August 2024

Abstract
This paper aims to present the impacts of severe slugging over Production SLWR design in a Pre-salt of Santos Basin project. This design criteria of slugging fatigue in steel pipe risers is not frequently used, once subsea systems are, whenever possible, designed to minimize the risk of operating under this regime. However, the subsea layout of some recent projects, with long descending flowlines towards rises basis, increases the risk of occurrence of this phenomenon, mainly under low flow rates, typical of field late life. While hydrodynamic slugging might induce high frequency riser response, severe slugging (terrain induced slug) is characterized by a much lower frequency (but higher amplitude), which leads to a much different riser behavior. Different conditions were assessed, comprising critical scenarios with satellite wells and wells connected to a high-pressure gas/liquid subsea separator (HISEP™), which changes the liquid holdup along the flowline, favoring severe slugging occurrence.
In steel pipe riser design, fatigue represents an important structural failure mode when accounting for all sources of cyclical loads that are expected during operational lifetime, such as: wave-induced motions, both current and heave-induced VIV and, lastly, internal fluid flow loads. This paper will focus on calculating severe slugging damage while performing a comparison among all sources’ percentual contribution to total damage in this studied scenario. This comparison shows that severe slugging heavily contributes to fatigue damage at a specific region located at the Touchdown Zone (TDZ). This critical region suffers mostly from internal fluid weight variation along the riser, which leads to low frequency but high amplitude stress variation.
The OLGA™ dynamic multiphase flow simulator [1] was adopted in order to model the subsea slugging flow and generate the required data for riser analysis, that is, pressure, fluid density, and velocity profiles along the riser pipe, during at least an entire slug cycle, allowing to characterize the fluctuations due to this flow. Afterward, time-domain structural analyses were performed with inhouse Petrobras’ riser analysis software Anflex [2] by having the above-mentioned profiles utilized as input data.
The state of practice for riser slugging fatigue analysis is not yet fully established. Even in guidance with industry standards, different practices and assessment methodologies between operators and projects can be found. It could be observed that uncertainties in reservoir parameters, premises on definition of flow parameters as the multiphase and slugging flow itself, design load cases with respective probabilities of time operation under this regimen and methodology adopted for riser dynamics modeling were crucial, representing Petrobras’ ongoing efforts to establish a robust and safe SLWR riser design.
Unsupervised Machine Learning for Well Log Depth Alignment
Authors: Acharya Sushil , Fabian Karl 
Published: August 2024

Abstract
Depth alignment as a prerequisite for subsurface geology interpretation aims to match signals of two logs from the same well to a common depth scale. Here, three consecutive unsupervised machine-learning techniques are applied to achieve this goal. First, data vectors are reduced through pre-processing with PCA and autoencoder methods, and clustered by K-means with K-means++ initialization. In a second step, corresponding cluster boundaries are identified to globally align lithologic units. This assumes that cluster boundaries represent physical changes in lithology, without direct lithological interpretation. The third step uses cross-correlation to obtain the final log alignment. Additional linear or non-linear interpolation between matching boundaries is sufficient to align well logs. Performance and accuracy of various techniques are compared by visual inspection and manually determined boundaries. Reducing data dimension with an autoencoder and K-means clustering performed best among tested methods. The study suggests that cluster-based methods can automate depth alignment of well logs without human intervention.
Analysis of Installation Time for Floating Offshore Wind Farms
Authors: Hasumi Tomohiro , Yokoi Takeshi , Haneda Ken , Chujo Toshiki , Fujiwara Toshifumi 
Published: August 2024

Abstract
It is essential to calculate installation time of a Floating Offshore Wind Farm (FOWF) by summarizing the process based on actual projects to estimate the offshore installation cost more precisely than before. The objective of this paper is to propose an installation time estimation model for FOWF that incorporates installation time for wind turbine mounting and submarine cables by expanding the installation time model of floating offshore wind turbine (FOWT), proposed previously. The results indicate that for the pre-anchoring process, loading time, and total time of pre-installation time per mooring line and tensile testing time per anchor in Japan are about ten, and five times longer, respectively, than those of Europe. As for submarine cables, time for connecting one-side of the riser cable to a floater, and time for trenching cables in Japan are six, and eight times longer, respectively, than the corresponding times in Europe. The reduction of installation time of the anchor-sharing technology is estimated to be 24% assuming a FOWF model. We conclude that a proposed model is validated reproducing the actual offshore installation and provides a common framework of the estimation of installation time of FOWF.
Preliminary Experimental Results of a Temporal Planning-Based System for Autonomous Inspection Using UGV
Authors: Hinostroza M. A. , Lekkas Anastasios M. , de Jonge Christian , Ivar Sagatun Svein , Luteberget Bjørnar , Transeth Aksel 
Published: August 2024

Abstract
Inspection and maintenance (IM) operations in offshore oil & gas platforms involve significant challenges due to the harsh conditions in such remote environments. Therefore, there is a need for robotic solutions that can accomplish IM missions autonomously, a goal that has become more feasible in the last years due to advances in instrumentation, perception and artificial intelligence (AI). In this paper, we present initial experimental results of the Taurob unmanned ground vehicle (UGV) performing autonomous inspection at Equinor’s K-Lab Test Centre, located in Haugesund, Norway. The proposed solution employs the simultaneous task planning (STP) algorithm, introduced by Furelos-Blanco in [1], as a high-level action planner. STP can take into account durative high-level actions, such as “visit a specific location”, “inspect a sensor”, or “take a picture of a specified component” and, in addition, can replan online in case of events such as low battery status, or the need to revisit a location. Communication with the robot is achieved via Equinor’s Integration and Supervisory Control of Autonomous Robots (ISAR) framework, which guarantees a fast and secure wi-fi connection. Two types of experiments were carried out: 1) A basic inspection round, which involves visiting a sequence of predefined waypoints; 2) A replanning scenario, which also takes into account the battery status. Our preliminary tests, where fast and efficient plans were computed and executed in real time, including replanning, showed that connecting the guidance and control system of a UGV with a high-level planner like STP is a promising approach to increased autonomy in IM missions.
Underwater Absorption Performance of a New Rubber-Based Acoustic Absorber Embedded With Composite Scatter
Authors: Wu Guanghua , Han Wei , Li Tianyun , Zhu Xiang 
Published: August 2024

Abstract
The acoustic impedance of rubber matches well with that of water, which makes rubber have a good performance for absorbing underwater noise. However, the effective absorption of underwater low-frequency sound is still a challenge. To solve the problem, a new rubber-based acoustic structure is proposed. Based on the coupling effect between cavity resonance and local resonance, the structure can effectively control the propagation of elastic waves. The absorption coefficient and displacement field distributions of the cavity-type structure, local resonant structure, and the proposed structure are compared to explain the energy loss mechanism. The material parameters of the proposed structure, such as the density of the inner hard core, and elastic modulus of soft rubber and rubber matrix, are changed to investigate the influence of material on absorption performance. In addition, the geometry shape of the cavity is varied, cone cavity and circular truncated cone cavity are introduced to analyze the influence of shape on absorption performance. The results show that the existence of the cavity enlarges the interaction effect between the hard core and soft rubber and increases the displacement of the rubber matrix in the vertical direction. The reduction of the elastic modulus of soft rubber and the increase of density of the hard core can improve the absorption coefficient. The cavity should be designed to be gradient to enhance the coupling effect to dissipate underwater low-frequency noise.
An Experimental Study on Effects of Aerodynamic Damping of a 5MW Semi-Submersible Floating Vertical Axis Wind Turbine
Authors: Jiang Yingying , Cheng Zhengshun , Chen Peng , Liu Lei , Yang Lijun , Xiao Longfei 
Published: August 2024

Abstract
Floating vertical-axis wind turbines (FVAWTs) offer certain advantages over floating horizontal-axis wind turbines (HAWTs), particularly in terms of the potential to lower the cost of energy. In this study, a 5MW FVAWT concept with three straight blades and a semi-submersible hull deployed in a water depth of 42 m was presented. In addition, the experimental setup is introduced, and calibration tests are also performed to validate the physical model system. The aerodynamic damping in surge and pitch motions was measured by comparing the decay experimental results with and without wind loads. Following this, wind/wave basin model tests with a scale ratio of 1/50 were conducted to explore the effect of aerodynamic damping on the motion characteristics of this turbine concept. Results indicate that aerodynamic damping can suppress the fluctuations of the platform’s surge and pitch motion at their respective resonance frequencies and tends to increase with wind speed at below-rated wind speed. Additionally, surge-induced and pitch-induced aerodynamic damping hardly affect the wave frequency response. Meanwhile, the surge natural frequency is substantially altered due to the wind loads. This study contributes to providing valuable insights into the aerodynamic damping of floating VAWTs.
A Comparison of Optimization Methods Applied to Surrogate-Based Optimization in Wind Farm Yaw Control
Authors: Tu Yu , Zhang Kai , Chen Yaoran , Han Zhaolong , Cao Yong , Zhou Dai 
Published: August 2024

Abstract
In wind farms, wake effects among turbines hinder optimal power generation, making collective yaw control crucial for efficiency. The accurate calculation of power generation for large-scale wind farm is time consuming and computationally expensive. To address this challenge, Surrogate-Based Optimization (SBO) emerges as an effective tool in the yaw optimization. In the design of experiment, wake effects are simulated by Gauss-Curl Hybrid (GCH) model in FLORIS. Based on the limited dataset, SBO utilizes surrogate models to approximate the relationship between yaw angles and total power in the entire design space, enabling a more efficient approach to yaw optimization. The selection of optimization algorithms within the SBO framework becomes pivotal, with the recognition that gradient-free methods excel in scenarios with multiple local minima, while gradient-based methods offer advantages in high-dimensional problems inherent in large-scale wind farms. This paper compares three optimization algorithms — Sequential Least Squares Quadratic Programming (SLSQP), Differential Evolution (DE), and Particle Swarm Optimization (PSO) — in the context of wind farm yaw optimization. Three yaw control case studies are presented, offering a comprehensive comparison of the strengths and limitations of the optimization algorithms. Results show that the gradient-free methods, balancing computational cost and accuracy, stand out as the preferred choice for wind farm yaw optimization. Despite the low-fidelity engineering wake model used in the current study, the SBO framework is also compatible with the higher-fidelity wind turbine models. This capability lays the foundation for optimizing yaw control under more realistic conditions.
Numerical Modelling of Novel Floating Offshore Wind Turbine Concept
Authors: Conway Oisín , Connolly Aengus , Leen Seán 
Published: August 2024

Abstract
This paper describes the numerical modelling of a novel floating offshore wind turbine (FOWT), a next-generation concept which aims to combine the best features of traditional spar and semi-submersible platforms, coupled with a modular design for ease of manufacturing and assembly. The study was conducted as part of Phase IV of OC6 (Offshore Code Comparison Collaboration, Continued, with Correlation and unCertainty), an international research project focused on verifying and validating numerical modelling tools used in the analysis of floating offshore wind systems. In this study, numerical modelling is performed using a mid-fidelity tool which performs fully coupled aero-hydro-servo-elastic simulations in the time domain. The simulation model is based on a full-scale demonstrator version of the FOWT concept hosting a 3.6 MW turbine, which has been deployed offshore and is fully operational since 2021. Results from the numerical model are validated by comparisons with experimental data from a 1:43 Froude-scale test performed in the University of Maine’s Ocean Engineering Laboratory. Beginning with fundamental test cases, including static equilibrium, surge offsets, and free-decay simulations, the scenarios advance in complexity to include wind-only loads, wave-only forces, and a combination of wind and wave conditions. Key parameters of interest include aerodynamic forces, motions of the floating support structure, tower base moments, mooring line tensions, and keel line tensions. Overall, the results show a strong correlation with the empirical data. This paper complements the research work undertaken in OC6 Phase IV, further substantiating its insights into the dynamic responses of floating offshore wind turbines.
Tsunami Actual Water Experience Museums
Authors: Hamada Eigai 
Published: August 2024

Abstract
The NPO Takurou (Chief Director : Eigai Hamada) is planning to construct museums where visitors can learn about how terrifying tsunamis are through actual water demonstrations and about measures to prevent tsunami disasters. The museums will provide actual tsunami-like water flow at a safe height so that visitors can experience the possible effects of tsunamis, such as their legs being directly exposed to rushing water and falling down into the water, so they can see how easy it would be to drown even in shallow water. The museums will also provide information (videos, photos, etc.) of previous tsunami disasters, such as that during the Great East Japan Earthquake and Tsunami of 2011, so that visitors can feel the fear of an actual tsunami. Also, the museums will provide lectures which teach about updated tsunami disaster mitigation measures, how to prevent tsunami disasters, and how to protect residents and their communities from tsunamis.
For visitors who are afraid to experience actual water flow or do not want to watch videos of previous tsunami disasters, medical staff will consult with the visitors and advise them on which exhibits to skip.
These Tsunami Actual Water Experience Museums will be established in two areas in Japan subject to tsunamis (i.e., Kuroshio in Kochi Prefecture and Taro in Miyako in Iwate Prefecture). The planned museums will revitalize the local communities, which are suffering under the threat of tsunamis and whose populations are declining as a result.
Generation of Extreme Waves With Partial Energy Focusing in Random Seas
Authors: Cui Junnan , Feng Xingya , Chen Qunbin 
Published: August 2024

Abstract
In recent years, extreme waves, which appear from nowhere with extremely large wave height in the ocean, have attracted extensive attention and research in academic and engineering fields. A simple linear model proposed by Tromans et al.–NewWave theory[2], has been widely used to explain the occurrence of extreme waves. The NewWave model requires that all frequency components in a random seastate focus at a specific time and location to generate a large wave group, which however is unlikely to happen naturally. In this work, we consider an otherwise more realistic condition where wave energies are only partially focused. Focused wave groups are generated by partial energy focusing using a JONSWAP wave spectrum and their characteristics are studied. The effects of different frequency components and bandwidths on the characteristics of wave groups are investigated. A high order spectral (HOS) model, which is validated by physical experiments, is utilized to simulate the propagation of partial focusing waves. Both second-order and fifth-order simulations are carried out to understand the influence of modulation instability. The nonlinear characteristics of partial focusing waves during its propagation are studied simultaneously. Overall, this work provides some new insights into the mechanism of formation of extreme waves.
Effects of Vertical Distance on Performance and Wake Characteristics of Two Offshore Wind Turbines With Various Lateral Distances
Authors: Li Haolong , Liu Yuanchuan , Chang Shuang 
Published: August 2024

Abstract
Offshore wind turbines are mostly arranged in wind farms in the form of arrays. The aerodynamic performance of downstream wind turbines decreases significantly due to the influence of upstream wind turbine wake. In addition to the streamwise distance, lateral and vertical distances can be imposed for adjacent wind turbines to achieve performance improvement of downstream turbines. In this paper, a large eddy simulation method based on the open source CFD platform OpenFOAM is applied to simulate the turbine blades in conjunction with an actuator line technique. The effect of vertical distance on performance and wake characteristics of two tandem offshore wind turbines in the presence of lateral distance is investigated.
The results show that both lateral and vertical distances can improve the performance of the downstream turbine. When turbines operate at the rated condition, imposing lateral distance improves the power output to a larger extent than raising the hub height of the downstream turbine, although not as much as raising upstream turbine. However, for the above rated condition, the impacts of turbine arrangement on performance improvement of the downstream turbine are opposite to the results obtained for the rated condition, and the increase in rotor power is considerably reduced. Wake characteristics of both turbines are analyzed to support the results.
Experimental Data and Modelling of Cable and Pipe Axial Friction on a Rocky Seabed
Authors: Griffiths Terry , Draper Scott , An Hongwei , Cheng Liang , Fogliani Antonino , White David 
Published: August 2024

Abstract
As part of recent research into the on-bottom stability of subsea pipes and cables on rocky seabeds, a set of physical model tests have been performed investigating the effective lateral and axial friction factors. The lateral friction factor experience led to a new model for the effective friction which scales up the cable-rock interface friction coefficient allowing for the roughness of the rocky surface that the cable moves over.
This paper presents the results of axial friction testing which showed a similar enhancement of friction linked to the roughness of the rock surface in a different way. These test results demonstrated that the axial resistance could also be many times greater than the interface friction force when the characteristic rock particle sizes are comparable to or greater than the cable diameter. This arises from a ‘wedging’ action that leads to inclined contact between the cable and the rock, which causes an increase in the sliding friction. Data and modelling of this behaviour is provided to assist application of these results to design.
Enhancing Offshore Wind Farm Met-Ocean Data Accessibility: A Machine Learning Approach With Satellite-Derived Wave Measurements in the Celtic Sea
Authors: Whistler Sophie , Ashton Ian G. C. , Pillai Ajit C. , Quartly Graham D. 
Published: August 2024

Abstract
Marine operations are a significant expense for offshore wind farms, representing up to one third of total project costs. An improved understanding of the variation of met-ocean conditions across a wind farm site offers the potential to reduce weather downtime and associated costs. This work employs a machine learning approach utilising a surrogate wave model trained on the relationship between the wave conditions at discrete measurement locations to wave conditions across the entire model domain. The surrogate model can then be run with real-time data inputs from the discrete measurement locations to provide a spatial dataset for waves, without the high computational power needed to run the physics-based wave model itself. This new method enhances the accessibility of met-ocean data to allow more informed decision making for the installation, operation, and maintenance of offshore wind farms.
The approach has already proven successful with fixed measurement buoys, and work is ongoing to adapt the modelling framework to use satellite-derived wave data as an input. With freely available global coverage, satellite data is a useful complementary data source to wave buoy data. Several Earth Observation satellite missions host radar altimeters that report significant wave height along the satellite’s ground track. The first step towards utilising radar altimeter data with the machine learning framework is assessing the impact of using only significant wave height data as measurement inputs. This paper compares the model outputs from running the model with wave height, period, and direction data, and with wave height data only. The results show that running the model with wave height data only produces a small reduction in the accuracy of output wave predictions in coastal areas.
Time Domain Prediction of Combined CF and IL VIV Responses Under Constant Currents
Authors: Wu Jie , Yin Decao , Lie Halvor , Passano Elizabeth , Baarholm Gro Sagli , Sævik Svein 
Published: August 2024

Abstract
The slender marine structure (e.g., deep water riser systems) subjected to vortex induced vibrations (VIV) can oscillate simultaneously in both cross-flow (CF) and in-line (IL) direction relative to the flow direction. The IL response is important as it may contribute to fatigue damage to the same order of magnitude as the CF responses for high mode responses. A combined CF and IL load model is also required for prediction of VIV responses in more complex flow conditions. The time domain VIV prediction load model has been extended to include an IL VIV load term. The present study aims to validate the latest combined CF and IL load model using laboratory tests and evaluate its limitations. The validation results showed that the averaged spatial and temporal energy transfer process between fluid and structure is sufficiently described by the load model. The time domain VIV load model is able to obtain reasonable prediction of key VIV responses, including curvature, frequency, fatigue damage, higher harmonic responses in both CF and IL directions as well as drag amplification in one single non-linear time domain analysis. This overcomes some of the limitations in the present frequency prediction models.