bluuebunny/crossref_metadata_2025_split huggingface dataset:
Echo State Networks for Surface Current Forecasting in a Port Access Channel
Authors: Marino Moreno Felipe , Fialho Coelho Jefferson , Sproesser Mathias Marlon , Rodrigues de Barros Marcel , Fabricio Deberaldini Netto Caio , Palmiro de Freitas Lucas , Dottori Marcelo , Gagliardi Cozman Fábio , Helena Reali Costa Anna , Satoshi Gomi Edson , Aoun Tannuri Eduardo 
Published: September 2023

Abstract
This work employs Echo State Networks (ESN) to improve one day ahead forecasts of water currents in a port access channel entrance, with the aim to provide a more accurate method that can be used to alert the port authority about unsafe conditions for navigation in the near future. For this task Leaky integrator Echo State Networks (LiESNs) are applied to predict one day ahead currents in the Santos channel, Brazil; The method has been trained with data obtained from an Acoustic Doppler Current Profiler installed in the channel, with data available between the years of 2019–2020. Results have been compared with the Santos Operational Forecasting System (SOFS), a numerical model already in use for the same region. Experiments show that the LiESN outperforms the numerical model by the metrics of Index of Agreement (0.922 versus 0.812) and RMSE (0.152 ms−1 versus 0.220 ms−1).
Numerical Simulation of Motion Responses of a Cabin-Suspended Catamaran in Head Waves
Authors: Han Jialin , Kitazawa Daisuke , Murai Motohiko 
Published: September 2023

Abstract
In this study, the motion responses of a suspension catamaran in head waves are presented using numerical calculation and experimental validation. The cabin-suspended ship has 9 degree-of-freedom, as the heave, pitch, and roll motion of the cabin can be separated from that of the twin-hull through a suspension unit. The suspension unit consists of four compression springs and linkages to guide the motion. The hydrodynamic coefficients and the wave exciting force/moments of the twin-hull were calculated using a potential flow solver named OrcaWave. A method was proposed to approximate the wave exciting force/moments at an advancing speed using the wave exciting force/moments at zero speed. The study analyzed the motion response of the ship at different damping coefficients and spring constants. The results show that motion reduction of the cabin by tuning only the spring constant and damping coefficient is limited, and different pairs of spring constant and damping coefficient would be needed for different wave encounter frequencies. The study provides valuable insights for the design of suspension ships to reduce motion responses in head waves.
Development of an IPM Tool for Subsea System Design Considering Lifetime Production/Injection Performance
Authors: Wang Yuxi , Hong Cheng , Estefen Segen F. 
Published: September 2023

Abstract
Rational conceptual design is a formidable task to ensure feasible and economic operation along offshore oil field development lifecycle. An integrated production modeling (IPM) approach has to be adopted at the conceptual design stage since it enables the assessment of the spatio-temporal interaction between the subsea pipeline network and the reservoir. This work reports the development of an computer-aided IPM tool to facilitate effective subsea scenario comparison and selection considering the lifecycle performance of both the production system and the injection system. Three performance indicators are used for scenario comparison and selection, namely, NPV, recovery rate, and wax-free index. A case study demonstrates the application of the IPM tool in assessing the effect of subsea water separation, for both green field design and brown field revitalization purposes. The developed IPM tool allows the production engineer to focus on the subsea configuration itself since production performance of each candidate scenario is effectively evaluated from autonomous simulation results under the same development logic.
Research on Lost Circulation Diagnosis Model Based on SMOTE-Tomek and Stacking Ensemble Learning
Authors: Han Liang , Song Xianzhi , Zhang Haolin , Lv Zehao , Zhou Detao , Zhu Zhaopeng , Yao Xuezhe , Zhang Rui 
Published: September 2023

Abstract
Lost circulation is one of the common risks in the drilling process, accurate and efficient lost circulation risk diagnosis is very important to ensure drilling safety. The risk diagnosis method based on machine learning has high efficiency and strong robustness, and is receiving more and more attention. However, the class imbalance of lost circulation/normal sample size seriously limits the performance of the machine learning model. Moreover, the stability and generalization of the intelligent model built using single algorithms are limited. To solve the above problems, SMOTE-Tomek algorithm is used to process the lost circulation dataset with unbalanced structure. And then random forest (RF), extreme gradient boosting (XGBoost) and support vector classification (SVC) are used to build the Stacking ensemble learning diagnosis model. Finally, the effects of the ensemble learning model and the single algorithm models are compared. The research results show that SMOTE-Tomek algorithm can effectively improve the diagnostic performance of the model for the risk of lost circulation, and the Stacking ensemble learning model has the best diagnostic effect, with its accuracy rate (96.40%), recall rate (92.74%), and missed alarm rate (7.26%) superior to the single algorithm model. This study is of great significance to ensure drilling safety and provide auxiliary reference for on-site control personnel.
Numerical Investigation of Internal Flow Effect on the Cross-Flow Vortex-Induced Vibration
Authors: Zhao Guixin , Meng Shuai 
Published: September 2023

Abstract
To examine the internal flow effect (IFE) on the vortex-induced vibration (VIV) of a flexible marine riser in the subcritical internal flow region, the cross-flow (CF) VIV of the riser with single-phase internal flows is investigated employing a semi-empirical hydrodynamic force model. The governing equation can be established based on Hamilton Principle and solved by finite element method. A MATLAB code has been developed and it has been validated for IFE and VIV respectively. The numerical simulations of a flexible riser are carried out with different internal flow velocities and internal flow densities. The IFE on CF VIV is investigated by analyzing the dominant mode, dominant frequency and displacement response of the riser. It has demonstrated that with the increase of internal flow velocity and density, (1) the dominant mode of VIV can transfer to a higher order, accompanied by a jump increase of the dominant frequency; (2) the increase or decrease of the root mean square displacement of VIV depends on whether the dominant frequency approaches or departs from the vortex shedding frequency; (3) the travelling wave characteristics of VIV can be enhanced.
Comparison Between Experiments and Simulations for a Ship Maneuvering in Waves
Authors: Ramachandran Krishnavelu , Borsutkar Visharad , Somayajula Abhilash Sharma 
Published: September 2023

Abstract
The current regulations of the International Maritime Organization (IMO) aims to increase the reduction of carbon dioxide (CO2) emissions from shipping by providing mandates to improve the Energy Efficiency Design Index (EEDI) of new ships. This has prompted newer vessels to be equipped with low-powered engines as compared to the previous vessels of similar size. However, the low power may potentially cause some vessels to be ill-equipped to maneuver effectively in the presence of waves. Although, traditionally turning characteristics of a vessel is considered in calm waters, in light of the new regulations it is important to consider course-changing ability in waves during the design process. This study aims to compare the maneuvering simulations and experiments of a scaled KRISO container ship (KCS) in calm water and in regular waves. The MMG standard method was developed by the Maneuvering Mathematical Group (MMG) which was organized by the Japan Society of Naval Architects and Ocean Engineers. This model is used to simulate the motions of the vessel in still water. A potential flow theory-based MDLHydroD software is used for calculating second-order wave drift forces and these drift forces are added to the MMG model. The simulations are compared with free-running model tests in both calm water conditions and in regular waves.
Seabed Proximity Effect on Free Spanning Pipelines: the FIST JIP
Authors: Caruso Mário , Sutherland James 
Published: September 2023

Abstract
Natural free spans occur in offshore pipelines when its stiffness prevents it from following the contours of the seabed., typically either due to the seabed contour or an erosion process after the pipe is laid. Free spans may be subjected to vortex induced vibrations that can lead to rapid accumulation of fatigue damage. Most offshore pipelines free spans occur in the proximity of the seabed. The influence of the seabed proximity on the hydrodynamic behaviour of the system is dictated by the span gap. When the seabed proximity significantly affects the flow around the pipeline in free span, the span may be considered a small gap span. When assessing VIV in small gap spans, current practice is to either nearly ignore the effect from proximity or to ignore VIV based on a critical gap approach. Previous research on crossflow VIV showed that both approaches are limited.
Thus, a joint industry project to study proximity effects in free spans in scour trenches, the FIST JIP, was formed. FIST JIP performed extensive test program focused on in-line VIV near seabed, with and without scoured trenches, to document the proximity effects. This paper presents the experimental work from FIST JIP and a suggestion to incorporate its results to better account for seabed proximity.
A Mesh Convergence Study for Low Frequency Second Order Wave Forces on Floating Bodies
Authors: Pan Zhiyuan , Kim Taeyoung , Heo Jaekyung 
Published: September 2023

Abstract
The second-order wave excitation forces acting on offshore floating structures are much more sensitive to mesh quality than linear forces when using the boundary element method to solve potential flow problems. This paper demonstrates the importance of mesh refinement near the waterline and sharp corners for mean drift forces, as well as low-frequency components in bi-chromatic wave conditions. To achieve better local panel refinement, a stretching factor is introduced to the Cosine spacing formulation used in meshing for the potential flow solver. This approach yields an economical and effective mesh for second-order analyses. An optimal mesh for a bottom-fixed cylinder is identified by comparing the horizontal mean drift force from numerical results against analytical values. Off-body kinematics near the cylinder are also studied as a basis for the mid-field formulation. A truncated floating cylinder is used to test the mid-field formulation applied for the vertical drift force. It is found that the drift force calculated by the pressure integration method matches well with the result obtained by the mid-field formulation when the sharp corner at the bottom is properly refined. Two ship models are then used to test the meshing strategy towards the waterline for second-order forces using both the near-field and mid-field methods. Recommendations are provided for meshing strategies on wetted hulls for boundary element method codes applied to low frequency second-order problems.
Preliminary Investigation of Ocean Wave Refraction Using an Array of Wave Energy Converters
Authors: Sergiienko Nataliia , Tuck William , Cannard Patrick , Georgiadis Mikaela , Capper Benjamin , Schultz Jesse , Cleggett James , Cazzolato Benjamin 
Published: September 2023

Abstract
Coastal erosion and its management cause significant economic, social, and environmental impacts on Australia. Current methods of controlling coastal erosion are expensive and are frequently damaged during severe weather events. However, recent studies have identified the potential for Wave Energy Converters (WECs) to provide a solution to this problem. WECs can extract energy from ocean waves and attenuate the wave field propagating towards the shore. The aim of this project is to determine whether arrays of WECs can not only reduce the magnitude of the propagated wave but also change its direction, thereby creating more favourable nearshore conditions.
The study is conducted using small-scale experiments in a wave flume using an array of ten oscillating water columns (OWC). The OWCs are placed perpendicular to the incoming wave and equally spaced across the width of the wave flume. The OWCs are constructed using L-shaped pipes of 60-mm diameter, and the natural frequency of each OWC is tuned using different horizontal pipe extensions, which ultimately change the mass of water within the OWC. The damping is tuned using end-caps with different orifice diameters. Each OWC is equipped with a pressure sensor to measure the differential air pressure inside the OWC air chamber. The downstream wave field is characterised using a row of 6 resistive wave gauges located at a distance of 2 m from the wave array. The study is conducted using regular waves with a wave frequency of 1 Hz. The preliminary results demonstrate that the array of OWCs can change the direction of the incoming wave by several degrees.
Fatigue Crack Propagation Prediction for Pipeline Steel Under Gaseous Hydrogen Environment
Authors: Zheng Tingsen , Chen Nian-Zhong 
Published: September 2023

Abstract
Hydrogen embrittlement (HE) refers to the irreversible damage caused by hydrogen diffused in the metal lattice with the metal material itself or other chemical elements in the matrix, which may lead to fatigue failure. Therefore, for safety reasons, it is of great significance to investigate the impact of HE on the fatigue strength of pipeline steel under gaseous hydrogen environment. Cyclic cohesive zone model (CCZM) is one of the potential methods for simulating the hydrogen assisted crack (HAC). A fatigue crack propagation simulation for API X52 pipeline steel based on a modified CCZM under gaseous hydrogen environment is performed in this paper. The modified CCZM is proposed where not only the degradation of cohesive strength but also the degradation of accumulated cohesive length is considered in order to clarify the impact of HE on the fatigue crack propagation. The degradation of cohesive strength and that of accumulated cohesive length is expressed with piece-wise linear relationships. The results of simulation are then compared with test results to demonstrate the capability of the proposed CCZM. The proposed model tends to provide a useful reference for further research on the simulation for HAC by CCZM.
Bayesian Updating of Estimated Parameters Representing Multi-Modal Directional Wave Spectrum Using Measured Ship Hull Stresses
Authors: Kubo Hiromi , Okada Tetsuo , Chen Xi , Kawamura Yasumi , Mitsuyuki Taiga , Hayakawa Ginga 
Published: September 2023

Abstract
To ensure structural safety of large container ships, advanced application of monitoring data is pursued. To estimate sea state in a probabilistic manner, in this paper, we attempted peak-by-peak Bayesian updating of the multi-modal directional wave spectrum estimated using the measured ship hull stresses. In addition, time history of the probability distributions of stress responses according to the obtained probabilistic sea state was discussed compared with the measurement.
Hydrodynamic Forces on Near-Bed Cylinders in Steady Currents
Authors: Hu Xiaoyuan , Cheng Liang , Tong Feifei , Teng Yunfei , Qu Yan , Jiang Hongyi 
Published: September 2023

Abstract
Numerical simulations are carried to investigate hydrodynamic forces and flow patterns around cylinder clusters of equally-spaced tandem cylinders closed to a plane wall in steady flow. The Reynolds number covered in the study are Re = 10000 and 200000. The number of cylinders in the cluster are 2, 3 and 6 with the spacing between the cylinders being 1, 2 and 4 and the gap to diameter D ratio (e/D) ranging from 0.1 to 1. The numerical results show that the sheltering effect of the leading cylinder in the cluster leads to significant reductions of hydrodynamic forces on the downstream cylinders in the cluster, for the parameter ranges considered in this study. A methodology based on the combination of low fidelity computational fluid dynamic simulations and reliable published force coefficients is proposed for estimating hydrodynamic forces acting on individual cylinders in the cluster.
Motion Suppression of a Floating Offshore Wind Turbine Using Heaving Point Absorbers: A Case Study in Australia
Authors: da Silva Leandro Souza Pinheiro , Y. Sergiienko Nataliia , S. Cazzolato Benjamin , Meng Fantai , de Oliveira Marielle , Ding Boyin 
Published: September 2023

Abstract
Hybrid platforms composed of a floating offshore wind turbine (FOWT) and heaving point absorbers (PAs) can be a promising solution to reduce project costs while improving the quality of energy and ocean space utilisation. Although this hybrid platform idea is attractive, wave energy converters (WECs) may transfer part of their energy to the FOWT via motion if the devices and their respective power-take off (PTO) systems are not properly designed, leading to undesirable loads. Based on that, an alternative option is the use of WECs to reduce the FOWT platform motions, while absorbing wave energy. This approach is particularly important in locations where both resources are abundant, such as in Australia, where the hybrid solution may extend the platform’s lifetime. In this general context, this work aims to investigate the use of PAs as a motion suppression device. The hybrid platform is assumed to be subject to realistic environmental conditions: turbulent wind (temporal and spatial effects) and irregular waves. The numerical model is built in the frequency domain, and important sources of nonlinearities are estimated using statistical linearisation. The performance of the hybrid platform is compared against the standalone FOWT for an offshore site in Sydney, Australia. Results demonstrate that depending on the PTO configuration, the hybrid platform has a superior response compared to the standalone FOWT, suppressing the horizontal nacelle acceleration by around 8% while extracting an additional 30 kW from waves.
Analysis of Turbulence Parameters for a Tidal Energy Site in a Wave-Current Environment
Authors: Tan Tian , Venugopal Vengatesan , Sellar Brian 
Published: September 2023

Abstract
Tidal power converters deployed in areas where waves and tidal currents coexist face high levels of turbulences, which can lead to unstable power generation and increase the risks of turbine blade fatigue failure. In order to improve the design and safety operation of tidal turbines in a combined wave-current environment, it is necessary to understand and characterise the turbulence parameters such as turbulence intensity (TI)/turbulent kinetic energy (TKE) etc. It is also important to characterise how waves and currents separately affect these parameters.
In this study, field data collected by an Acoustic Doppler Current Profiler (ADCP) at the Pentland Firth, Orkney Islands, Scotland, are analysed to evaluate the levels of TI produced separately by waves and tidal currents. The empirical mode decomposition (EMD) method has been utilised for this analysis. At first, using the EMD, the velocity components corresponding to waves and tidal current components are separated. In order to verify the separation methodology, a two step process is adopted. In step one, wave component velocities are converted to significant wave heights using linear wave transfer function. For the second step, the significant wave heights obtained from step one are compared with the same hindcast by a coupled wave-current numerical model. A very good match between wave heights is observed with a correlation coefficient of 0.8, thus validating the methodology followed. Then, the depth-varying vertical profiles of the turbulence intensity (TI) of the decomposed wave and current components are calculated. It is found that the streamwise wave-induced TI is about 5% at the height of 15m where the turbine hub is placed, while the tidal current-induced TI is 10%–17%. The wave-current combined TI is 13%–20%. This study has demonstrated a methodology to successfully separate and quantify turbulence intensities produced individually by waves and tidal currents when they coexist at a site.
Deepwater RCM and SRI Design of Production Rigid Flowline Loops
Authors: Chatzimanolis Nikolaos , Jalali Hossein , Bedrossian Arek , Xie Min , Lewis Mark 
Published: September 2023

Abstract
Deepwater High Pressure High Temperature (HPHT) rigid flowlines laid on large slope seabed morphology, with complex operational loading and multiple subsea well tie-in locations, impose significant design challenges. This paper presents a novel thermomechanical design for production flowline loops which involves the deployment of deepwater Residual Curvature Method (RCM) and Subsea Rock Installation (SRI). It focuses on the RCM engineering which ensures that the design satisfies all the criteria for any as-landed angle of the RC sections; i.e. irrespectively of the level of rolling of the RC sections during installation. This design accounts also for the effect of the cooldown of thick insulated flowlines, on the seabed just after pipelay from as-laid to ambient seawater temperature, on their response. The effects of soil berms on the initial formation and through-life performance of the lateral buckles at RC sections are discussed. Moreover, the design accounts for the through-life response of the engineered lateral buckles at locations of relatively high transverse slopes. Furthermore, the reliability of the RCM is demonstrated with a deterministic approach. Additionally, this paper presents a comparative study which demonstrates the lower carbon footprint of RCM relative to that of sleepers. Finally, the paper discusses the deployment of SRI to partially restrain the flowlines and control their axial displacements at critical locations to acceptable levels.
A Dynamics Experiment With a Submerged and Suspended Vertical Riser Pipe Small Scale Model Undergoing Forced Motions at the Top
Authors: Cesar de Oliveira Trigo Caio , Bordalo Sergio Nascimento , Morooka Celso Kazuyuki 
Published: September 2023

Abstract
The present work describes a laboratory experiment with a small scale model of a vertical marine riser with a free lower end and with forced motions at the top end, inside a water tank. Long and slender flexible vertical riser pipes are very common in offshore operations. They are used in drilling rigs for re-entry operations in subsea petroleum wellbores, they are employed to elevate cold water from the deep ocean in order to refrigerate equipments in the floating petroleum production facility at the sea surface, among other purposes, and they are also used to lift mineral slurry mixtures in seabed mining operations.
In the present experiment, the transversal movements of the model along its length were recorded over time. This paper describes the experimental set-up and the optical measurement system developed to obtain the model’s displacements. The challenges and solution to find a satisfactory material for the pipe model are commented and the design of the small scale model is discussed. Numerical simulations for the model’s vibrations were computed to evaluate the measurement results. Advancements were developed for the experimental procedure and modeling, including the testing mechanism and the instrumentation to measure the main parameters of the dynamic behavior of the vertically suspended and submerged flexible pipe model.
The experimental method used herein could be extended to other configurations and conditions with the proper scaling and design of the physical set up, and consequently be applied to various offshore operations dealing with the exploitation of natural resources and energy of the oceans.