bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Conceptual Large Autonomous Subsea Freight-Glider for Liquid CO2 Transportation
Authors: Xing Yihan 
Published: October 2021

Abstract
The produced fluids in a subsea field development can be transported from the subsea well to a floating production unit using pipelines where they are thereafter offloaded to a tanker (surface ship). The flow direction is reversed in the case of CO2 injection into the subsea well. This CO2 offloading process is highly dependent on the weather conditions and it cannot be performed when the conditions are severe. Furthermore, subsea pipeline systems can be expensive to install and maintain. In the present study, a novel subsea freight-glider system is proposed as a suitable, cost-effective, energy-efficient alternative to tanker ships and pipelines. The proposed vehicle is autonomous, 50 m long, has a 1500 DWT displacement, and can carry approximately 800 tons of cargo. The subsea freight-glider uses variable-buoyancy propulsion instead of traditional propellers/thrusters. It changes ballast to provide positive and negative net buoyancy which allows it to glide subsea through the water using hydrodynamic wings. This is an extremely energy efficient way of transporting large amounts of cargo over medium/long distances. Since the subsea freight-glider operates underneath the sea surface, it is not affected by wind and waves and can operate in any weather condition. Furthermore, subsea fields that are not large enough to justify the installation of subsea pipelines can still be developed. Even though the subsea freight-glider is proposed as a vehicle for liquid CO2 transport, it can also transport different types of cargo such as hydrocarbons, injection fluids and gasses, and even carry electrical power using batteries.
Failure Mechanism and Limit Load Capacity of Subsea Pipelines With Dent Defects
Authors: Chen Yanfei , Zong You , Dong Shaohua , Yan Yufeng , He Guoyan , Hou Fuheng 
Published: October 2021

Abstract
With the development of oil and gas resources extending to the deep sea, more and more submarine pipelines are applied, and the importance of the structural and functional integrity of submarine pipelines is becoming more and more prominent. Dent has long been considered one of the potential factors affecting the integrity of submarine pipelines, which can be formed when pipelines are impacted by fallings objects from the sea surface. Due to the seabed subsidence, pipeline suspension and earthquake, mudslide activity and other factors, submarine pipelines may be under bending moment, seriously affecting the safe operation of submarine pipelines. The study of failure and limit load capacity of submarine pipelines under external pressure and bending moment is of great significance. In this paper, the nonlinear finite element method is used to study the collapse failure and local buckling failure of subsea pipelines under external pressure and bending moment respectively. The process of the pipeline being dented by the impact of objects is simulated, spherical denter and wedge-shaped denter are considered. The influence of D/t and dent depth on collapse capacity and bending capacity are investigated. The results can be referred in engineering practice.
Evaluation of Belleville Springs and Damping Through Static Cyclic Loading “Hysteresis” for pVARD Optimization: Part-I
Authors: Abugharara Abdelsalam , Butt Stephen 
Published: October 2021

Abstract
One unconventional application that researchers have been investigating for enhancing drilling performance, has been implemented through improving and stabilizing the most effective downhole drilling parameters including (i) increasing downhole dynamic weight on bit (DDWOB), (ii) stabilizing revolution per minutes (rpm), (iii) minimizing destructive downhole vibrations, among many others.
As one portion of a three-part-research that consists of a comprehensive data analysis and evaluation of a static compression hysteresis, dynamic compression hysteresis, and corresponding drilling tests, this research investigates through static cyclic loading “Hysteresis” of individual and combined springs and damping the functionality of the passive Vibration Assisted Rotary Drilling (pVARD) tool that could be utilized towards enhancing the drilling performance.
Tests are conducted on the two main pVARD tool sections that include (i) Belleville springs, which represent the elasticity portion and (ii) the damping section, which represents the viscous portion. Firstly, tests were conducted through static cyclic loading “Hysteresis” of (i) a mono elastic, (ii) a mono viscus, and (iii) dual elastic-viscus cyclic loading scenarios for the purpose of further examining pVARD functionality.
For performing static compression tests, a calibrated geomechanics loading frame was utilized, and various spring stacking of different durometer damping were tested to seek a wide-range data and to provide a multi-angle analysis.
Results involved analyzing loading and displacement relationships of individual and combined springs and damping are presented with detailed report of data analysis, discussion, and conclusions.
Agree – Disagree: Comparing Traffic Limitations in the Kara Sea
Authors: Kim Ekaterina , Panchi Nabil 
Published: October 2021

Abstract
This study investigates variability of ships’ operational limitations for ice conditions in view of national rules and international recommendations (the Rules for Navigation in the Water Area of the Northern Sea Route and the International Maritime Organization Recommendations). As an example, the Kara Sea region is considered for the period of 2017–2019. The ship data from two datasets were considered: (1) the Northern Sea Route Administration data and (2) the Automatic Identification System data. For each ship’s ice class, the ice information (concentration and type) was used to derive operational limitations based on the Polar Operational Limit Assessment Risk Indexing System (POLARIS), and the results were compared with the newly updated Northern Sea Route access criteria. Preliminary results indicate that national rules are generally stricter than international recommendations, however on some occasions, the national rules impose lesser restrictions on operations as ships with ice class PC7/Arc4 are allowed to operate when the international recommendations suggest an elevated probability of an accidental event.
Comparison of Different Modeling Techniques for Solid-Fluid Interface for Wave Loading
Authors: Saladin Tara , Kwon Young W. , Klamo Joseph T. 
Published: October 2021

Abstract
Computational fluid dynamics (CFD) has been used to estimate the wave loading applied to a fully submerged body near the surface. The Navier-Stokes equations were used for the present study. In terms of modeling the fluid-solid interface, two different techniques are available in ANSYS CFX. One is the Rigid Body Method (RBM) and the other is the Immersed Solid Method (ISM). This paper compares the two modeling techniques in terms of accuracy and modeling flexibility. For this study, a CFD model of the NPS tow tank with wave generation and a submerged body was created to investigate different methods of solid body modeling. A comparison of the RBM and ISM was performed modeling a submerged rectangular body at different depths. The models produced similar results when the body was lower beneath the wave surface with limited fluid-solid interaction. As the amount of fluid-solid interaction increased, the RBM showed increased amounts of wave energy dissipation as compared to the ISM. This disruption of the wave energy resulted in the RBM showing smaller body forces and moments when compared to the ISM solid model. The increased wave energy dissipation in the RBM is likely caused by the different mechanism for modeling body-solid interaction. The numerical results were also compared to the experimental data.
Enhancing Machine Learning Models With Prior Physical Knowledge to Aid in VIV Response Prediction
Authors: Ma Leixin , Resvanis Themistocles L. , Vandiver J. Kim 
Published: October 2021

Abstract
Practical engineering prediction models for flow-induced vibration are needed in the design of structures in the ocean. Research has shown that structural vibration response may be influenced by a large number of physical input parameters, such as damping and Reynolds number. Practical response prediction tools used in design are inevitably a compromise between complexity and simplicity of use. Modern machine learning tools may be used to identify which input parameters are most important. Standard machine learning techniques enable the researcher to compile a list of the most important input parameters, ranked or ordered by the effect of each on the prediction error of the model. When all inputs are treated as equals, blind application of machine learning may lead to predictions that are inconsistent with prior physical knowledge. To address this problem, we conducted a parameter selection process using a prior knowledge-based, trend-informed neural network architecture. This approach was used to identify features important to the prediction of the cross-flow vibration response amplitude of long flexible cylinders, given the known prior effect of Reynolds number and damping. The model balances the usual goal of minimizing the model prediction error, but doing so in a manner that closely follows the extensive knowledge we have of the influence of Reynolds number and damping parameter on response. The resulting neural network model was able to reveal additional insights, including the role of mode number shifting, mode dominance and travelling waves in the regulation of VIV response amplitude.
Hydrodynamic Coupling of Viscous and Non-Viscous Numerical Wave Solutions Within the Open-Source Hydrodynamics Framework REEF3D
Authors: Wang Weizhi , Pákozdi Csaba , Kamath Arun , Martin Tobias , Bihs Hans 
Published: October 2021

Abstract
A comprehensive understanding of the marine environment in the offshore area requires phase-resolved wave information. For the far-field wave propagation, computational efficiency is crucial, as large spatial and temporal scales are involved. For the near-field extreme wave events and wave impacts, high resolution is required to resolve the flow details and turbulence. The combined use of a computationally efficient large-scale model and a high-resolution local-scale solver provides a solution the combines accuracy and efficiency. This article introduces a coupling strategy between the efficient fully nonlinear potential flow (FNPF) solver REEF3D::FNPF and the high-fidelity computational fluid dynamics (CFD) model REEF3D::CFD within in the open-source hydrodynamics framework REEF3D. REEF3D::FNPF solves the Laplace equation together with the boundary conditions on a sigma-coordinate. The free surface boundary conditions are discretised using high-order finite difference methods. The Laplace equation for the velocity potential is solved with a conjugated gradient solver preconditioned with geometric multi-grid provided by the open-source library hypre. The model is fully parallelised following the domain decomposition strategy and the MPI protocol. The waves calculated with the FNPF solver are used as wave generation boundary condition for the CFD based numerical wave tank REEF3D::CFD. The CFD model employs an interface capturing two-phase flow approach that can resolve complex wave structure interaction, including breaking wave kinematics and turbulent effects. The presented hydrodynamic coupling strategy is tested for various wave conditions and the accuracy is fully assessed.
Effect of the Installation Process on the Pullout Capacity of Helical Anchors
Authors: El Haj Abdul Kader , Soubra Abdul-Hamid 
Published: October 2021

Abstract
In this paper, an advanced numerical method called Coupled Eulerian-Lagrangian (CEL) method is used for the prediction of the behavior of helical anchors in sandy soil under ultimate limit state ULS including the effect of anchor installation process. The CEL analysis allows one to overcome the drawback of the classical finite element FE method in the case of large deformation problems as it takes the advantages of both Lagrangian and Eulerian methodologies. Results have shown that the CEL analysis is relevant for the computation of the helical anchor pullout capacity. Indeed, the CEL analysis was able to rigorously determine the ultimate capacity of the anchor contrary to the classical FE method; the calculation via the CEL approach has been carried out for relatively large displacement values without encountering any problem of convergence. Furthermore, CEL analysis was able to simulate the installation process of the anchor and thus enables one to consider the effect of the soil disturbance induced by the installation process on the computed pullout capacity. The numerical simulations have shown that the pullout capacity of the helical anchor may be significantly decreased when considering the anchor installation effect.
Determination of the Vertical Location of the Axis of Rotation of the Roll Motion From Full-Scale Measurements
Authors: Johnsen Lars , Krüger Stefan 
Published: October 2021

Abstract
The behavior of a floating structure results from the mechanics of its, more or less, rigid body and the hydrostatic and hydrodynamic forces acting on it. Particularly for ships, as long and slender bodies, the axis of roll and its vertical position is of special importance. It is around this axis that the lowest lateral accelerations in roll motion occur, which is not only weakly damped but also easily stimulated due to the relatively low mass moment of inertia around the ship’s longitudinal axis. With the intention of clarifying some widespread misconceptions about the location of this axis and to investigate its relation to the natural roll period, full scale measurements have been carried out using a set of two mobile Inertial-Measurement-Units. The Inertial-Measurement-Units were placed on different heights, one above and one below the assumed location of the axis of rotation. Based on the measured accelerations and angular velocities, the average vertical location of the axis of the roll motion for small angles is determined.
Using Computer Simulations to Aid the Analysis of Fluid Contaminations During Cement Plug Placement
Authors: Wang Shuai , Dai Hu , He Liang 
Published: October 2021

Abstract
Setting a cement plug on the target zone either creates a solid seal to stop fluid movement or provides a kick-off point for sidetrack drilling operations. Successfully placing cement plugs is one of most critical steps to ensure trouble free completion, reduce the risk of loss of circulation, isolate pressure zones and enhance wellbore integrity.
The traditional method is to pump all the fluids until each fluid level is equal to that inside the string. The limitation to this method is that the fluid could be contaminated once the string is pulled out of the hole, due to variable fluid densities, as well as wellbore and work string sizes. Thus, the volume of spacers pumped ahead and behind the cement and the volume of displacement are critical to the quality of the cement plug.
A computer program is developed to model the displacement hydraulics of fluids and simulate fluids contamination during pulling pipe out of hole. The computer modeling aids in optimizing the pumping schedule to ensure balanced slurry and spacer levels after POOH (Pull out of the hole), minimizing contamination within the cement slurry and spacer, ultimately, reducing the risk of loss of circulation and enhancing wellbore integrity.
Effects of Design Parameter on Occurrence of Snap Load and Wear of Mooring Line for Spar-Buoy With Ring-Fin Motion Stabilizer for Shallow Sea
Authors: Yamamoto Yusuke , Morimoto Taishi , Katayama Toru , Goto Masahiro , Kodama Ryo 
Published: October 2021

Abstract
The purpose of this study is to propose an optimal design method of the spar-buoy with ring-fin motion stabilizer for shallow sea and its mooring system, in order to avoid the occurrence of snap load. The mechanism of occurrence of snap load is investigated by model tests, and design parameters for avoiding the occurrence of snap load are investigated. From the observation of model’s motion, it has been realized that the snap load is caused by the tension of mooring line to stop the buoy’s horizontal motion, which relaxes the mooring line. Moreover, it has been confirmed that the horizontal motion is caused by the horizontal forces acting on the center pipe and float of the buoy, which relates to the acceleration component of wave excitation forces.
In this paper, the effects of changing of design of the buoy (: diameter of center pipe and float, size of stabilizer, density of the buoy, length of mooring line) on avoiding or reducing snap load are investigated by using a numerical simulation (OrcaFlexver.11.0b), and the wear amounts are also estimated by using an empirical method (Takeuchi et al., 2019). From the results, it is confirmed that changing the buoy’s motion mode by shortening mooring line is effective to avoiding the occurrence of snap load, and to reduce the wear amount of the mooring line.
Numerical Simulation of a Jumper Conveying Slurry for Deep-Sea Mining
Authors: Yamamoto Marcio , Fujiwara Tomo , Yamamoto Joji , Masanobu Sotaro 
Published: October 2021

Abstract
One key technology for Deep-Sea Mining is the riser system. The riser is already a field-proven technology in the Petroleum Industry. However, several differences exist between a petroleum production riser and a riser for Deep-Sea Mining, mainly related to the internal flow. The ore-slurry has a larger density than the hydrocarbons and shall be pumped with a much higher flowrate.
The current software tools for riser’s dynamic analysis may include the internal fluid hydrostatic pressure and the centrifugal and Coriolis forces imposed by the bent pipe’s internal flow. However, the internal pressure drop is not calculated. The internal pressure alters the pipe’s effective tension and can alter the pipe’s bending moment changing its mechanical behavior.
This article describes a computational script’s development to run embedded in a commercial software for riser’s dynamic analysis. Our script calculates the internal viscous pressure drop along with the jumper. This pressure is then converted into wall axial tension (buckling) and imposed on each node of the jumper’s numerical model.
Each simulation case was calculated twice with and without the internal flow viscous pressure drop. The comparison with experimental data revealed that the jumper’s average position has a good agreement among all cases. However, the amplitude caused by the top oscillation showed some discrepancies. Experimental data has the highest amplitude in the horizontal direction, while the simulation without viscous pressure calculation had the smallest. The simulation with our embedded script had intermediary amplitude in the horizontal direction. The vertical direction amplitudes have the same behavior for all cases, but the experimental data showed the highest amplitude.
Tangguh Project: Multidisciplinary and Challenging Design of a Novel Concept of Buckle Initiator
Authors: Federico Formentini , Foschi Luigi , Guidi Filippo , Iannucci Ester , Marchionni Lorenzo , Zulkarnain Yansa 
Published: October 2021

Abstract
This paper is based on the experience made during the design and installation of an offshore pipeline recently completed in Indonesia, where a 24” subsea production pipeline (16km long in 70m water depth) was found susceptible during design to lateral buckling. To limit the development of excessive deformation within the acceptance criteria, a mitigation strategy based on interacting planned buckles has been adopted installing three Buckle Initiators (BI) along the pipeline route.
Buckling is a well understood phenomenon. However, this project was characterized by major uncertainties mainly driven by soil characterization, soil-pipe interaction, seabed mobility and soil liquefaction. These uncertainties have played a key role in the in-service buckling design. A lot of engineering efforts have been spent to go through the screening between alternative concepts, the validation of the chosen solution and its detailed engineering phase. This paper discusses the main contributing factors and how the uncertainties have been tackled.
The Buckle Initiators are quite large and heavy structures with two main bars: the first ramp has an inclination equal to 30° and the pipeline has been laid on it; a second horizontal ramp was used as sleeper to accommodate the development of the lateral buckle during the operating life. A rotating arm was also used to restrict the pipeline lay corridor on the inclined ramp guaranteeing a combined horizontal and vertical out-of-straightness in the as-laid configuration. The rotating arm has been released as soon as the pipeline passed the BI permitting the pipeline to slide freely over the two BI ramps. The foundation of the Buckle Initiator has a footprint surface of about 60m2 guaranteeing its stability for different soil types characterizing the three installation areas. This more complex solution was preferred with respect to a typical sleeper to increase the robustness of the system in terms of buckle mobilization.
The design of the Buckle Initiator was a multidisciplinary activity where many novel concepts were developed and many issues were faced (i.e. pipeline laying on an inclined sleeper, anti-scouring system, foundation design, etc.). The Buckle Initiator design was focused on structural calculations against design loads expected during temporary and operating conditions, geotechnical verifications, installation analysis, pipeline configuration and fatigue assessment.
This paper presents all main engineering aspects faced during design and first feedbacks from field after the pipeline installation.