bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of Integrated Acoustic Communication and Positioning System for Operation of Autonomous Underwater Vehicles and a Sea Trial
Authors: Watanabe Yoshitaka , Kondo Satoshi , Meguro Koji , Shimura Takuya , Deguchi Mitsuyasu , Kida Yukihiro 
Published: September 2023

Abstract
An integrated acoustic communication and positioning system for the operation of autonomous underwater vehicles (AUVs) was developed, in which the acoustic communication function and positioning functions are integrated and the transmission timing of acoustic packets is controlled to efficiently use time and frequency resources. A chip scall atomic clock (CSAC) is equipped with the system and the systems on each vehicle are synchronized. The propagation time of the acoustic packet is then measured with one-way time (OWT) of flight and information of transmission time. In the integrated and synchronized mode, uplinks (ULs) from AUVs are periodically transmitted, and transmission timing of downlinks (DLs) from autonomous surface vehicle (ASV) is controlled to avoid collision of the ULs and DLs. A sea trial was conducted in a deep-sea area with a water depth of 1,100–1,150 meters. Four AUVs were simultaneously operated with an ASV for positioning and monitoring the AUVs using the developed acoustic system with the integrated and synchronized mode. The AUVs cruised for 2.5 hours near the seabed. The developed system worked well and the sea trial was successfully performed. The period of hull swing of the ASV was rapid owing to its small body and the Doppler effect was varied quickly; however, the acoustic communication was stable. Positioning and control of transmission timing was successfully achieved. On the other hand, an improvement in the accuracy of positioning is desired for operation in deep water areas.
Flexible Pipe Fatigue Life Evaluation Based on a Dynamic Full-Scale Test Considering a Preconditioning Corrosion Procedure
Authors: Brun Coser Tiago , Sulino de Negreiros Luiz Antonio , Carneiro Campello George , Duarte Radke Erik , Delwing Rosa Carolina , Fonseca De Souza Derek , Venturini Rodrigues Luiz Francisco , Renck Tiago Samuel , dos Reis Tagliari Mariana , Favaro Borges Marcelo 
Published: September 2023

Abstract
In this work, a systematic approach was adopted to evaluate the fatigue resistance of a flexible pipe with corroded tensile armour wires. A mid-scale test apparatus was developed to expose a short flexible pipe section to a controlled corrosive environment. After the exposure period, four-point bending fatigue tests were carried out using corroded tensile armour wire samples obtained from the preconditioned short flexible pipe sample. The results were compared with a reference SN curve and it was possible to observe the detrimental effect due to the preconditioning procedure. Parallel with the mid-scale test execution, a full-scale flexible pipe sample was preconditioned with the same corrosive environment used for the short sample. After 12 months, a dynamic tension-to-tension test was conducted and the fatigue damage imposed during the test was calculated. It was possible to observe a better correlation between the full-scale test result and the estimation done when the SN curves of pre-corroded armour wires was used. Even though further studies need to be carried out, current results show that the consideration of SN curves obtained from corroded tensile armour wires would increase reliability and accuracy in flexible pipe fatigue life assessments.
Identification of Interacting Free Spans in a Subsea Pipeline
Authors: Saraswat Rajil , Patil Palash , Ciecko Edward , Koul Parul 
Published: September 2023

Abstract
Free span in pipelines can occur intentionally either due to the seabed topography during laying, or it can be caused by scouring of the seabed during operation. A free span section can either be on its own which is known as ‘single span’ or multiple spans can be in close vicinity and form a ‘multi-span’. The unsupported section (free span) of the pipeline in presence of currents has a potential of causing vortex induced vibration (VIV). In such a scenario, the pipeline can vibrate along the flow direction (inline) or perpendicular to it (crossflow). This is detrimental to the pipeline especially to the welds, as this leads to the accumulation of fatigue damage leading to a reduction in fatigue life.
The recommended practice DNV-RP-F105 ‘Free Spanning Pipelines’ [1] lays out the methodology to assess fatigue in free-spanning pipelines. In a multi-span scenario, the spans in close vicinity may interact with each other. The morphological classification plot (release 2006 Figure 1-2) in the DNV-RP-F105 provides means to decide whether the span is interacting based on relative lengths of the spans and intermediate shoulder. In a recent update of the DNV-RP-F105 (2017), this classification plot was called out as inaccurate. Additional guidance was added describing an algorithm to assess whether a span is a single span or an interacting multi-span.
In this work the new guidance was used to classify the spans as isolated or interacting for an existing pipeline. The free spans were identified through a survey of the pipeline using multibeam echosounder and sidescan sonar. The multi-spans were identified from the free span listing. For each multi-span multiple finite element (FE) models were developed to compare the modal response of the multi-span against each span member. A comparison was also made with the morphological classification plot to check its validity.
Semi-Analytical Load Models Accounting for the Tilt and Motion of a Cylinder Impacted by a Plunging Breaking Wave
Authors: Renaud Paul , Hulin Florian , Batlle Martin Marc , Scolan Yves-Marie , Tassin Alan , Jacques Nicolas , Harris Jeffrey C. , Filipot Jean-François 
Published: September 2023

Abstract
This work is part of the DIMPACT project that addresses breaking-wave-induced loads on floating wind turbines. In this context, the hydrodynamic impact of a strong plunging breaking wave on a cylinder is studied using semi-analytical models, with a focus on the loads sensitivity to the cylinder tilt and wave-cylinder relative motion.
Two semi-analytical models are applied in a strip theory approach under the Froude-Krylov assumption. A numerical wave is generated using a Fully Nonlinear Potential Flow (FNPF) solver, whose free surface geometry and kinematics feed the semi-analytical models. Semi-analytical slamming loads are compared with force measurements collected in a wave flume for different pitch angles and surge speeds. The temporal variation of the force as well as the maximum force acting on the cylinder are well estimated by the semi-analytical models. A new engineering formula is finally developed, accounting for the inclination and surge motion of the cylinder. The impact loads computed with this formula also show good agreement with the experimental tests.
Predicting Weather Down Time for an Offshore Wind Turbine Installation Vessel (WTIV) With Feeders Using Rapid Spectral RAO-Based Hindcast Vessel Motions in Wave Environment
Authors: Mohtat Ali , Hertel Melissa , Hooper Christopher , Jors Charles , Souquet Benjamin , Van Gundy Coulston 
Published: September 2023

Abstract
The relatively new source of alternative energy, offshore wind energy, has brought many new challenges into the logistics and maritime operations in the north America. “Jones Act Maritime Law” prohibits foreign flagged vessels from transporting cargo between locations within the U.S. territorial sea. This restriction means Offshore Wind Turbine Installers can either build new Wind Turbine Installation Vessels (WTIV) in the United States, or transport wind turbine generators (WTG) using coastwise qualified feeder vessels and foreign WTIVs. The constraints on the motion and acceleration of WTG components may limit operations or require motion compensation systems. To support system design, a tool is required that allows the user to evaluate the difference is uptime between different vessels, load conditions, motion compensation equipment and lifting appliances. Traditional weather down time analysis evaluates operations against hind cast environmental data. The method described here expands the weather downtime simulation to include cargo motions and accelerations and vessel responses. The results can then be used to evaluate the relative value of each feeder type or motion compensation system to inform installation system design, risk analysis and contracting.
The model is applied to analyze multiple candidate feeder vessels and various turbine models, transit routes, and installation sites covering 41 years of hourly hindcast data. To accommodate this scope, a technique is applied to rapidly compute vessel motions using pre-computed Spectral Response Amplitude Operations (SRAOs) at each hindcast time step. The SRAO database has parameters of wave heading (ϕ), modal period (Tp), significant wave height (Hs), directional cosn spreading, and spectral shape (γ). SRAOs are referenced for each wave condition to approximate motions in wind waves and swell. This method offers quick turnaround, simulating millions of hours of hindcast vessel motions in a few hours of computational time on a 120-core cluster. Weather uptime for this sensitive operation is drastically increased in some instances when the feeder vessel can be aligned to the predominant wave direction. By capturing the underlying hydrodynamics in the proposed simulation, the method presented here can be applied to understand project schedule risk and fleet logistics during the project planning stages. This model can be further leveraged to offer operational guidance to the vessel operator during the wind farm construction phase.
Spatial-Temporal Evolution Of The Regional Shipping Network: A Case Study of Ports Along the Maritime Silk Road
Authors: Zhou Yong , Luo Shihui 
Published: September 2023

Abstract
Since the 21st Century Maritime Silk Road (MSR) initiative was launched in 2013, sixty-five countries and regions have already joined the construction of the MSR, and the development of blue economy has gradually become an international consensus. In order to investigate the impact of the MSR initiative on port developments and regional economy, this paper focuses on analyzing the spatial-temporal dynamics and evolution of shipping network among and within port clusters along the MSR. Specifically, a shipping network consisting of ports along the MSR and shipping routes is firstly built based on the complex network theory. Then a variety of data related to port infrastructure and operation as well as regional economy are collected and processed. With the aid of Herfindahl-Hirschman index (HHI) and Zipf’s law, the shipping network will be analyzed from the perspectives of network structure and market shares and size distribution of the involved ports. The results can be used to understand the changes in the pattern of seaborne trade along the MSR, and provide decision support for the sustainable development of economic globalization and regional economic integration.
From Offshore Flexible Flowlines to Dynamically Installed Anchors – A Concept Study
Authors: Hu Yuxia , Gao Minghui , Draper Scott , Hossain Muhammad Shazzad 
Published: September 2023

Abstract
Decommissioned subsea flexible flowlines and umbilicals pose a particular waste management challenge as there is limited capacity to process these materials in Australia. Approximately 3200 km of flexible flowlines and umbilicals will be decommissioned in Australia over the next 3 decades. Research can play a significant role in developing and validating approaches to better recycle and repurpose these flowlines and umbilicals, and at a broader scale redefine how industrial waste is managed in Australia.
This paper presents a concept study on designing new dynamically installed anchors using decommissioned flexible flowlines for supporting offshore floating facilities such as floating wind turbines, wave energy converters and floating aquaculture cages. For testing, a new model anchor was designed as if the anchor shaft was truncated from a decommissioned flexible flowline and ‘fish-scales’ were serrated on the external plastic layer of the flowline to enhance anchor holding capacity after installation. The new model ‘fish-scale’ anchor and model conventional deep penetrating anchor were tested for hydrodynamic and geotechnical characteristics. Their performances during free-fall in water and during penetration in clay were compared. The preliminary test results provided confirmation on the concept that decommissioned flexible flowlines could be turned into dynamically installed anchors with potential better performance.
Effect of Nonlinearity on Tubular Joint of Jacket Structure and its Response Under Dynamics Loading
Authors: Kumar Ram , Kumar Deepak 
Published: September 2023

Abstract
The jacket structure is one of the most important offshore structures. It’s a relatively stiff structure because its base is fixed to the foundation. Due to the fixidity at the bottom its natural period of vibration is much small in comparison to other floating structures. A jacket structure is framed structure that is generally made of tubular members and each member is connected rigidly. Under a huge load of platform and ocean waves, the member’s connection/joint undergoes rotation and deformation. Due to rotational and deformational responses at joints, the nonlinearity develops, and depending on structure properties and load it can be significant enough to affect the responses of the overall jacket structure. In this study, the joint of the jacket structure is remodeled using an analytical technique available in the literature, and the effect of the angle between the members is considered one of the factors for the nonlinearity in its flexibility matrix. The present study shows that considering the changing angle between the members shows a higher degree of nonlinearity in the flexibility matrix. Further, the same joint is modeled in Abaqus software for understanding the analytical results obtained previously. Further, buckling of the tubular member at the joint level due to external load is also considered in Abaqus for obtaining the relationship between load and displacement. This helps in obtaining the nonlinear stiffness matrix in the concerned degrees of freedom under the consideration of varying angles between members and buckling at the joint level of the tubular member. Further, the obtained nonlinear stiffness matrix is utilized to do the dynamic analysis of the joint in its concerned degree of freedom. Study shows that the nonlinear effect of joint is considerable enough and its effect is visible on dynamic response.
LSTM-Based Model Predictive Control for Motion Stabilized Platform of Doppler Lidar for Offshore Wind Observation
Authors: Kinugasa Mizuki , Yamamoto Yusuke , Terada Daisuke , Katayama Toru 
Published: September 2023

Abstract
In this study, the applicability of a controlled method based on LSTM (Long Short Term Memory) to motion reduction of a rigid body swing as a motion stabilized platform to place on floating platform is investigated numerically. First, for a single pendulum type motion stabilized platform on a spar-buoy type floating platform with tension-mooring, the sequential control torque required to cancel external torque is calculated. Next, one step ahead motion velocity and acceleration of the spar-buoy are predicted by using LSTM model, which is a kind of machine learning model for time series forecasting. Based on the predicted results, the effectiveness of model predictive control to reduce its motion is tried to be confirmed. However, it is difficult to reduce the motion because of prediction error. Then, skyhook dumper is applied to damp undesired control torque caused by the error. As the result, its pitch becomes less than one degree on the moderate wave condition, and magnification factor of motion amplitude of the single pendulum type motion stabilized platform becomes less than one.
A Systematic Approach for Developing a Numerical Wavetank to Simulate Driven Shallow- and Deep-Water Waves
Authors: Rehman Wajiha , Bokhove Onno , Kelmanson Mark 
Published: September 2023

Abstract
Numerical models of wavetanks for nonlinear waves driven by waveflap/piston wavemakers are developed. Variational principles (VPs) for the underlying equations of nonlinear potential-flow dynamics are implemented directly in the finite-element-based environment Firedrake. The establishment of mathematical and numerical wavetank models, based on VPs and domain-specific compiler architecture, is a novel challenge aimed at both reducing time-to-development and enabling new model experimentation. The waveflap-wavemaker problem is fundamentally more complex than the piston-wavemaker problem since reformulation of the mathematical problem into a computational domain respectively demands multi- and single-step transformations because of the respective two- and one-dimensional wavemaker motions. Hence this paper presents a systematic approach for developing a numerical piston/waveflap wavemaker wavetank, within the widely available Firedrake environment, that can simulate the dynamics of both shallow- and deep-water waves.
Experimental Modeling of Water-Wave Interactions With a Flexible Beam
Authors: Rehman Wajiha , Bunnik Tim , Bokhove Onno , Kelmanson Mark 
Published: September 2023

Abstract
A series of fluid-structure-interaction (FSI) experiments is presented for studying water-wave interactions with a flexible beam in a wide range of sea conditions thus yielding a variety of FSI test-case data. The aim is to use these experimental data in order to validate FSI solvers commonly employed by the maritime industry in the design of fixed-foundation, offshore wind turbines. The experimental setup allows simultaneous measurements of beam deflections and their effect on incident and reflected waves. In addition, the study is carried out in a wide range of sea conditions ranging from regular-to-irregular and moderate-to-extreme wave height and steepness. The study of such a wide range of conditions makes the experiments suitable for providing reliable data in the validation of a suite of mathematical and numerical FSI solvers, i.e., linear, nonlinear and high-fidelity. The data from the experiments will be made publicly available through open-source data-sharing platforms.
Aerodynamic Investigation of Tower Shadow Effects on the Horizontal Axial Dual-Rotor Wind Turbine
Authors: Zhao Mengshang , Zha Ruosi , Wang Kai , Wu Xiaodi , Chen Siqi 
Published: September 2023

Abstract
In this paper, unsteady numerical simulations for horizontal axis dual-rotor wind turbines with and without a tower were carried out using the actuator line model (ALM) instead of the traditional body-fitted mesh and the large eddy scale (LES) turbulence model to improve the numerical accuracy of the wake. The power coefficient Cp, axial force coefficient Cz and velocity distribution in the near wake were used to validate the accuracy of ALM based on model experimental results of a conventional wind turbine. The results indicated that ALM can accurately predict the aerodynamic performance and wake characteristics which agreed well with the experimental data. Tower shadow had little influence on average aerodynamic performance. But, it can significantly increase the fluctuation amplitude of the dual-rotor wind turbine. Both 1-time RF (rotational frequency) and 2-time RF were nearly noticeable for the dual-wind turbines in the case with a tower, while 2-time RF was obviously remarkable for the dual-rotor wind turbine in the case without a tower. The distribution of the transverse velocity was generally symmetrical in the near wake of 1-5D away from the wind turbine, but the distribution of the longitudinal velocity lost symmetry due to the tower shadow. However, the tower shadow had a negligible effect on the velocity recovery in the far wake.
Impact of Cleaning Efficiency on Disc Cutter Drilling Performance
Authors: Akindele Oluwatimilehin Mary , George Judith Onyedikachi , Abugharara Abdelsalam , Butt Stephen D. 
Published: September 2023

Abstract
Large diameter drilling operations, including tunnel boring and raise boring, are capital-intensive projects. As such, proper estimation of time and cost is critical to the planning of the drilling project. To arrive at the correct estimation of the drilling time during the drilling phase, accurate prediction of the drilling performance is needed. In large diameter applications, disc cutters are the primary cutting tools, hence, several investigations have focused on developing accurate estimation of disc cutter forces. Other studies have also sought to understand the impact of rotary speed and cutter geometry on drilling performance. This study seeks to contribute to existing body of knowledge by evaluating the impact of cuttings cleaning efficiency on disc cutter drilling performance. This technical paper presents the results of two sets of drilling experiments. Both experiments were conducted under atmospheric condition on the same granite block using same rotary cutting machine and tri-disc disc cutter with tungsten carbide inserts. Same drilling parameters were applied during each of these experiments. However, the difference lay in the adopted cuttings evacuation method. One drilling procedure adopted the dry method wherein the cuttings were evacuated with vacuum while in the second procedure, the cuttings were cleaned using the jetting action of a high spray nozzle. The results of these experiments show how much influence the cleaning efficiency has on the disc cutter drilling performance.
A New Multi-Criteria Decision-Making Tool for Subsea Oil and Gas Asset Decommissioning
Authors: Caprace Jean-David , Lourenço De Souza Marcelo Igor , Violante Ferreira Claudio , Ribeiro Nicolosi Eduardo 
Published: September 2023

Abstract
The designed life of many offshore O&G facilities is reaching its end. Decommissioning these facilities has become a critical task due to unpredictable costs, high operational risks, potential social impacts, and finally, environmental protection issues. Decision making plays a decisive role in finding a trade-off between the concerns and interests of stakeholders such as O&G companies, government bodies, environmental protection organizations, sea and coastal environment users, and local communities. The decision problem is often complex as it usually involves several criteria. Most of the time, there is no one perfect option available to suit all the criteria: an ‘ideal’ option does not usually exist. Therefore, a compromise must be found. To address this problem, the decision-maker may use advanced approaches such as Multi-Criteria Decision Analysis (MCDA). These models have recently attracted the attention of the industry. Here, we describe a new tool that improves the decision-making process ranking the different decommissioning options of O&G subsea assets. This model considers 37 attributes gathered into 6 criteria: Safety, Environment, Waste management, Technical, Social, and Economic. Several decommissioning alternatives are compared. The new tool has been tested on the Brazilian decommissioning of Espadarte Field, showing remarkable performance in aiding the decision-making process.