bluuebunny/crossref_metadata_2025_split huggingface dataset:
Feasibility Study of S-Lay Installation for Deepwater SCRs and Pipelines
Authors: Hou Jing , Yu Chenteh Alan , Cheng Yongming , Bangalore Gurudutt , Song Hao 
Published: December 2020

Abstract
The J-lay and S-lay are two common methods for SCR and pipeline installations. When using the S-lay installation method, onboard welded pipe joints leave the vessel horizontally and are guided to the seabed over a stinger structure. The pipe is lowered using tensioners. With the advantage of high production rate, Slay can be a cost-effective solution for deepwater riser and pipeline installation. Based on HYSY201 installation vessel, this paper investigates the feasibility of S-lay installation for deepwater SCRs and pipelines to be used in South China Sea.
It first introduces the SCRs and pipelines to be used for a deep draft semi-submersible for the Lingshui 17-2 project. It then presents the S-lay installation vessel HYSY201 and S-lay configuration. The hydrodynamic motion analysis for a Response Amplitude Operator (RAO) was computered for HYSY201 in different environmental headings. With the site-specific metocean design basis, this paper presents an installation procedure, analysis methodology, and acceptance criteria.
The study covers different sizes of SCRs and pipelines to investigate the feasibility of S-lay installation. The study starts from the static installation analysis of SCRs and pipelines and includes different installation steps. The acceptance criteria are examined for the pipes at over bend and sag bend regions. The support reactions load on the stinger structure are reported at each step. The dynamic analysis is selectively performed to evaluate Dynamic Amplification Factors (DAFs) of support reaction loads especially for roller box supports on the stinger structure. The sensitivity of DAFs to wave parameters such as wave height and peak period is analyzed as well.
The extreme support reaction loads are computed for evaluating the strength performance of the stinger structure. The feasibility of S-lay installation for deepwater SCRs and pipelines is determined by the global performance of SCRs and pipelines, installation vessel hold back tension and A&R winch load capacity, and performance of the stinger structure.
Based on the study work, this paper finds the feasibility of S-lay installation of deepwater SCRs and pipelines for Lingshui 17-2 project using the installation vessel of HYSY201.
Nonlinear Time-Domain Simulation of the Heaving-Buoy Type Wave Energy Converter by Using Three-Dimensional Potential Numerical Wave Tank Under Irregular Wave Conditions
Authors: Kim Sung-Jae , Koo Weoncheol , Kim Moo-Hyun 
Published: December 2020

Abstract
The aim of this paper is to evaluate the hydrodynamic performance of a heaving buoy type wave energy converter (WEC) and power take-off (PTO) system. To simulate the nonlinear behavior of the WEC with PTO system, a three-dimensional potential numerical wave tank (PNWT) was developed. The PNWT is a numerical analysis tool that can accurately reproduce experiments in physical wave tanks. The developed time-domain PNWT utilized the previously developed NWT technique and newly adopted the side wall damping area. The PNWT is based on boundary element method with constant panels. The mixed Eulerian-Lagrangian method (MEL) and acceleration potential approach were adopted to simulate the nonlinear behaviors of free-surface nodes associated with body motions. The PM spectrum as an irregular incident wave condition was applied to the input boundary. A floating or fixed type WEC structure was placed in the center of the computational domain. A hydraulic PTO system composed of a hydraulic cylinder, hydraulic motor and generator was modeled with approximate Coulomb damping force and applied to the WEC system.
Using the integrated numerical model of the WEC with PTO system, nonlinear interaction of irregular waves, the WEC structure, and the PTO system were simulated in the time domain. The optimal hydraulic pressure of the PTO condition was predicted. The hydrodynamic performance of the WEC was evaluated by comparing the linear and nonlinear analytical results and highlighted the importance accounting for nonlinear free surfaces.
CFD Simulation on Dynamic Installation of the Light-Weight Gravity Installed Plate Anchor in Clay
Authors: Liu Jun , Bu Nanqiao , Han Congcong 
Published: December 2020

Abstract
A light-weight gravity installed plate anchor (L-GIPLA) is put forward in the present study to secure offshore floating structures, such as floating wind turbines, floating net-cages, wave and tidal energy converters, and floating oil and gas platforms. The L-GIPLA is installed with the aid of a booster, which can be connected at the tail of the anchor during dynamically installation and retrieved after installation. The L-GIPLA owns the advantages of dynamically installation, deep penetration depth and high capacity efficiency. In the present study, the dynamic installation process of the L-GIPLA with a booster in clay is modelled by conducting three-dimensional large deformation analysis in commercial software ANSYS CFX, which is a computational fluid dynamics (CFD) software based on the finite volume method (FVM). Non-Newtonian fluid model, incorporating the strain-rate and strain-softening effects, is used to simulate the undrained clayey soil. Various factors influencing the final penetration depth of the anchor have been studied. These factors include the soil strength characterizations (strain-rate and strain-softening effects), and impact velocity. The results show that the L-GIPLA can obtain a relatively deep penetration depth in the seabed, indicating the L-GIPLA is an efficient alternative in offshore engineering.
A Study of Detecting for Dragging Anchor
Authors: Saito Akira 
Published: December 2020

Abstract
Frequent attack of typhoon leads to crucial accidents caused by anchor dragging. In 2018, 21st typhoon hit west of Japan and the vessel, which was fallen into anchor dragging, collided with the bridge connecting Kansai International Airport and opposite shore. This accident had serious damage to the transportation of people and logistics. Moreover, when 15th typhoon in 2019, which gave crucial damages such as house damages and suspension of the electric power and the water supply, hit Chiba prefecture located in east of Japan, 107 vessels which were equivalent to one third of all vessels anchored in Tokyo Bay had the symptom of anchor dragging.
Seafarers must take measures as precaution to anchor dragging. However, missing its opportunity causes irreparable disasters. As the attack of typhoon becomes more frequent and serious, the means, which can evaluate the risk quantitatively to anchor dragging and help them make a decision, are necessary because seafarers have possibilities to fall into unexpected situation even if they are skilled and familiar with ship’s characteristics.
This study aims at detecting the signal of earlier stage of anchor dragging and visualizing the level of danger, as a mean to make a decision for taking precautions in an appropriate opportunity. With the acceleration meter, which can measure quantitatively ship’s lists and vibrations what human cannot recognize, acceleration data of ship’s motion were measured and evaluated. However, they don’t always show necessary factors for analyzing ship’s motion because they include all motions on the ship, such as wind, wave force and vibrations from its generator.
Then, the system, sorting of each range of frequency from measured accelerations and extracting necessary data, was created. This enables extraction of ship’s motion at anchor. The analysis results between the outer force affecting to the ship at anchor and the data extracted by this system, specified the signal of anchor dragging. In addition, the new system was built for indicating the risk of anchor dragging, by evaluating relationship between the signal of anchor dragging and the effect by outer force.
Measuring their data on actual ship showed the validity of this system. Thus, with measuring acceleration data at anchor and analyzing them, detecting ship’s motion, which indicates the signal of anchor dragging, proved to be possible.
A New Type of Robot Used for Deep Stratum Drilling in Seabed
Authors: Zhang Peihao , Chen Jiawang , Tian Zhenwei , Ren ZiQiang , Ge Yongqiang , Gao Qiaoling , Gao Feng 
Published: December 2020

Abstract
With the increasing scale of the exploitation of ocean oil and gas resources, the decomposition of natural gas hydrate and the exploitation of submarine oil will damage the engineering mechanical structure of submarine sediments, leading to submarine collapse, landslide, even earthquake and other geological disasters, seriously threatening the exploration and exploitation of Marine resources. Therefore, it is necessary to develop a deep-seabed drilling robot to carry out real-time long-term monitoring of changes in the seabed environment by carrying sensors and detection devices. This paper will describe the design structure of the drilling robot, and explain the working process through that the drilling robot is released from the sea bed into the stratum of the mining area, and can achieve autonomous drilling and steering functions in the seabed stratum. In this paper, theoretical analysis and simulation verification will prove the feasibility of the robot moving in the stratum.
Quantitative Wear Estimation for Floating Structures by Using 3-D Geometry of Mooring Chain
Authors: Takeuchi Takaaki , Utsunomiya Tomoaki , Gotoh Koji , Sato Iku 
Published: December 2020

Abstract
For reducing the maintenance cost of floating offshore wind turbine structures, it is necessary to establish a quantitative wear estimation method for the mooring chains. In this paper, attempts have been made to improve the accuracy of the estimation method in terms of the mooring chain model. These investigations were performed about a spar-type floater moored with three catenary mooring lines at Goto, Nagasaki prefecture, Japan.
Up to now, the mass-spring model had been used for the mooring chain in response analysis and the relative angle between two spring lines was considered as only a sliding angle without friction. However, there is also rolling in the motion between mooring links, which should cause less wear than by sliding. In this study, the detailed motion of the link in response analysis is calculated and applied to the wear estimation by using a 3-D model in MSC. Adams. This enables the wear estimation considering link motion closer to a real phenomenon. A Contact analysis between the 3-D chain model requires some contact properties (e.g. contact stiffness and friction). In this paper, these properties are calculated based on the Hertzian contact method and FEM analysis.
As a result, the wear amounts overestimated by using the mass-spring model in the previous investigation, especially at the point located clump weight and touchdown point, decrease getting closer to the measurements. In addition, by tracking the contact points it is found that the major motion caused between links is the rolling. For future works, there remains a need for further validation and the consideration of elasticity between mooring links, impressions caused by proof load test and the effect of corrosion.
Numerical Study on the Hydrodynamic Performance of the DARPA Suboff Submarine for Steady Translation
Authors: Takahashi Kenshiro , Sahoo Prasanta K. 
Published: December 2020

Abstract
This study was built upon previous works conducted by the authors in a series of numerical studies on submarine hydrodynamics and is aimed at enhancing the accuracy of computational fluid dynamics (CFD) application processes, which estimate the hydrodynamic performance of underwater vehicles for steady translation conditions in the horizontal and vertical planes. In an earlier work, the computed straight-ahead resistance of a submarine agreed with those of experiments within a comparison error of 2%. However, a maximum comparison error of approximately 20% was obtained for sway force under a steady translation condition. The Defense Advanced Research Projects Agency (DARPA) Suboff submarine model was adopted as a benchmark, and the computational modeling was based on the Reynolds-averaged Navier–Stokes (RANS) turbulence model for steady simulations. The curvature correction approach was tested to improve the computation of circumferential flow around the cylindrical hull, in particular. The dominant maneuvering coefficients were calculated using the computed forces and moments as a function of the yaw and pitch angles along with simplified equations of motion by fitting a curve to the plots. The hydrodynamic forces and moments exerted on the stern plane were individually computed using a locally refined mesh around the tail section.
It was confirmed that the curvature correction approach improved the computational accuracy for the steady translation conditions, and general trends were captured over the tested yaw and pitch angles. However, some data points had notable comparison errors. Some of the estimated maneuvering coefficients agreed well between the CFD simulation and the experiments, whereas others had considerable comparison errors. The individually computed forces and moments exerted on the stern plane that had attack angles were inconsistent with those obtained in experiments. Those comparison errors may have been amplified by the complexity of configuration and arisen from differences in the experiments, such as the presence of a free surface and supporting strut to mount the hull to a carriage, and, perhaps, the geometrical differences owing to machining accuracy.
The investigation of flow field at the propeller plane revealed that the wake distributions inside the nozzle were significantly affected by the angled stern planes; the reduced velocity area was expanded and shifted. Furthermore, harmonic analysis of the wake fraction was conducted, and several primary nth harmonics were observed, which were associated with the struts and stern planes. This result suggests the risk of higher noise levels associated with the number of blades.
Line Type Optimization of the Flexible Jumper for New Generation Subsea Suspended Manifold Production System
Authors: An Weizheng , Li Zhigang , Luo Wentao , Wang Yingying , Duan Menglan 
Published: December 2020

Abstract
A new generation of subsea production system with the suspended manifold as the major characteristic was proposed to solve the disadvantages for hard to be discarded and recovered for the traditional subsea manifold fixed in seabed. Here, the flexible jumpers connecting the dry trees in the subsea functional chamber to the suspended manifold, can not only provide enough mooring forces as the mooring system, but also transport oil and gas from dry trees, which is an indispensable part of a complete new generation of subsea production system. So how to optimize the flexible jumpers to guarantee a good hydrodynamic performance is quite essential. In this paper, a steep wave type of flexible jumper is optimized by changing the suspended height, connection width, and position and diameter of the buoyancy block. The result shows that the location and the size of the buoyancy block both have a great influence on the distribution of the mechanical property and the line type of the flexible jumper while the influence of suspended height and connection width is very small. Calculations and analysis demonstrated that changing the position of the buoyancy block has no effect on the maximum tensile force of the flexible jumper, but the farther the buoyancy block is from the seabed, the larger the minimum bending radius of the flexible jumper is. Meanwhile, the larger the diameters of buoyancy block becomes, the larger the maximum tensile force is, and the smaller the minimum bending radius will be.
Study on Estimation of Flow Around Marine Propeller by Large-Scale LES and Affection of Grid Resolution and Reynolds Number
Authors: Fujisawa Takeharu , Tsubokura Makoto , Tanaka Hisao 
Published: December 2020

Abstract
To develop a ship with higher propulsion performance, accurate estimation method is required. Tthe performance of ships is estimated by both experimental methods using scale models and numerical methods based on computational fluid dynamics (CFD) using Reynolds average Navier-Stokes equation (RANS) models. Experiments with scale models have limitations regarding fast execution and cost reduction due to physical constraints, and we believe it is important to improve numerical methods. Adjustment of turbulent models can improve the estimation accuracy of numerical methods, but it is necessary to continuously compare and verify the numerical and experimental results. There is a limit to the improvement of the estimation accuracy of the numerical method with RANS models.
Direct numerical simulation (DNS), which can be solved without modeling the turbulence field, can acquire an accurate flow field, but it is difficult to implement because it requires a huge number of grids. In a large eddy simulation (LES) model, if the grid resolution (filter size) is fine, the limitations imposed by the model itself are reduced. LES performed with a sufficiently fine grid resolution may be able to achieve the comparable estimation accuracy as DNS without a high computational load. We considered this method to be promising for accurately estimating ship performance.
This is an initial study of a ship performance estimation calculation method using large-scale LES. We performed LES calculations with up to 6.4 billion cells for propeller open water test and obtained basic knowledge about large-scale LES calculations. We carried out calculations with different grid resolutions under the same operating conditions, and with different Reynolds numbers at the same resolution to show how the grid resolution and Reynolds number affect the estimation of propeller performance and flow around the propeller.
Water Wave Diffraction and Radiation by a Submerged Horizontal Circular Cylinder in Front a Vertical Wall
Authors: Li Ai-jun , Liu Yong 
Published: December 2020

Abstract
This article studies water wave diffraction and radiation by a submerged horizontal circular cylinder in front of a vertical wall under the assumption of linear potential flow theory. Based on the image principle, the hydrodynamic problem of a horizontal cylinder in front of a vertical wall is transformed into an equivalent problem involving symmetrical cylinders in a horizontally unbounded fluid domain. Then, analytical solutions for the present physical problem are developed using the method of multipole expansions combined with the shift of polar coordinate systems. The wave exciting forces on the cylinder as well as the added mass and radiation damping due to the cylinder oscillation are calculated. The analytical solutions converge very rapidly with the increasing truncated number of multipoles. Calculation examples are presented to examine the effects of different parameters on the hydrodynamic quantities of the cylinder. Results indicate that the hydrodynamic quantities of the cylinder in front of a vertical wall greatly differ from those in a horizontally unbounded fluid domain.
Model Tests on the Parametric Resonance of the Deep Draft Semi-Submersible Under Regular and Irregular Waves
Authors: Li Chenglin , Yu Liwei , Wang Shuqing , Tian Zhe , Wang Xujie 
Published: December 2020

Abstract
Model tests on the parametric resonance of the deep draft semi-submersible (DDS) under regular and irregular waves are conducted in the wave flume of the Ocean University of China (OUC). Model tests with and without mooring lines are conducted under various regular and irregular waves with different wave angles. From the results of the model without mooring lines, it is found that parametric resonance generally occurs when wave period is about the natural period of heave and about half of the natural period of pitch or roll. The steady amplitude of the parameter resonance is larger under larger wave height. In heading waves, parametric resonance occurs in the roll direction, while parametric resonance occurs in both roll and pitch direction for the beam wave. In irregular waves, parametric resonance is practical non-ergodic. For the model without mooring lines, parametric resonance does not occur under the constraints of the mooring system.
Experimental and Numerical Study of an Obliquely Towed Ship Model in Confined Waters
Authors: Terziev Momchil , Elsherbiny Khaled , Tezdogan Tahsin , Incecik Atilla 
Published: December 2020

Abstract
In this study, the forces and moments acting on the KCS ship model as a result of oblique towing at 10 and 20 degrees drift angles are evaluated experimentally and numerically via a commercial Reynolds averaged Navier-Stokes solver. For the purposes of this work, the KCS hull is modelled both experimentally and numerically at a scale factor of 1:75. The adopted case-studies feature both horizontal and vertical restrictions. Thus, the subject of this work is the oblique motion of a ship in a narrow canal with a depth of h/T = 2.2. The relative impact of turbulence modelling is assessed by comparing the computed integral quantities via several eddy-viscosity closure strategies. These include significant variants of the k-ϵ and k-ω models as well as a widely used one-equation closure. Multiphase numerical simulations are performed at several of the experimentally investigated depth Froude numbers for each drift angle condition in order to fully capture the physics of the problem at hand. The present study aims to provide a quantitative evaluation of the performance of the adopted turbulence models and recommended the best closure strategy for the class of investigated problems.
Investigation of Thermal Effects on Gas-Oil Stratified Flow Wax Deposition
Authors: Chi Yuandao , Daraboina Nagu , Sarica Cem 
Published: December 2020

Abstract
Two-phase flow wax deposition is a flow-pattern-dependent phenomenon. The thickness and hardness of the deposit vary along the pipe circumference. In this work, two-phase gas-oil stratified flow wax deposition experiments at various liquid and gas flow rates have been conducted systematically using Garden Banks condensate and natural gas in a 2-inch I.D. multiphase flow loop under the pressure of 350 psi. Both deposit mass and wax content increased as superficial gas and liquid velocities increased. The local deposits were observed to be thinner but harder at the sides compared to the bottom of the pipe.
Meanwhile, the cross-sectional deposits were crescent-shaped with an increasing local wax mass flux along the circumferential direction. The local multiphase hydrodynamic and heat transfer characteristics are known to play an essential role in the wax deposition process, and the temperature gradient is critical for establishing the concentration gradient. Thus, it is paramount to have a proper understanding of the local momentum and heat transfer to predict wax deposition in multiphase flow accurately.
Therefore, numerical simulations with an SST (Shear Stress Transport) k∼ω turbulent model was implemented to understand local heat transfer in two-phase gas-oil stratified flow. After each simulation, the ANSYS CFD-Post was used to export, visualize, and analyze the simulated results. A total of 19 locations were selected for circumferential sampling to analyze the local heat transfer in the model. Detailed information on liquid volume fraction, shear stress, and temperature were analyzed. It has been observed that the local shear stress, temperature gradient, and inner wall temperature decrease with increasing θ. The thickness of the thermal boundary layer increases as θ increases due to reduced Nuθ. The comparison between the localized Nuθ and Nu from unified heat transfer model has revealed that variation in Nuθ is critical in the circumferential heat transfer calculation and wax deposition modeling.