bluuebunny/crossref_metadata_2025_split huggingface dataset:
Real-Time Measurement of Eccentricity in Primary Cementing of Oil and Gas Wells
Authors: Maleki Amir , Frigaard Ian 
Published: November 2019

Abstract
We propose a new method to measure eccentricity of the annulus in real-time during primary cementing. Our methodology is based on seeding the displacing fluids with neutrally buoyant particles. The process of seeding can happen by a specially designed bottom plug that releases a particle every few seconds. Particles at different azimuthal position experience a different axial velocity, because of the eccentricity of annulus. We infer the local velocity of the fluids by tracking the trajectories of particles and correlate it to the local eccentricity of the annulus. We show that this methodology allows us to find an axial profile of eccentricity along the well, and helps to identify geometrical irregularities, such as washouts, along the annulus.
Impacts of Educational Outreach on Envisioning Marine Cities of the Future Development Project
Authors: Yoshida Ikuo 
Published: November 2019

Abstract
Given today’s changing global environment and the need for people to be able to lead prosperous lives in the future, we will need technical experts who can think flexibly and respond to change, and we will also need to provide opportunities for children to awaken and develop their interest in relevant technical areas. I have used lectures and seminars on the Marine Cities of the Future Development Project [1][2], a project in which I am deeply engaged, as opportunities to verify the impact of educational outreach on students. In these lectures, I emphasize aspects such as “pushing the boundaries” and “realizing goals through reliable technology,” and tailor the content to stimulate students’ career aspirations in STEM fields. Requests from educators for further lectures aimed at cultivating students’ career aspirations and students’ heightened interest in proposals of new technology as revealed by post-lecture surveys, confirm that these efforts have had the intended effect.
Development of YS 500MPa Class Thick Steel Plate With Weld Joint CTOD Property for Offshore Structures
Authors: Terazawa Yusuke , Ichimiya Katsuyuki , Ueda Keiji , Igi Satoshi , Suwa Minoru , Tanaka Toshitaka , Tsuji Akiyoshi 
Published: November 2019

Abstract
Recently, the installation areas of offshore structures has expanded into deep sea areas, and as a result, strength and plate thickness of the steel plate required for the offshore structures have become higher. And the main property of offshore structure steel is the crack tip opening displacement (CTOD) property of multi-pass weld joint. Thus, the developed steel was designed to improve HAZ toughness of multi-pass weld joint. Firstly, in order to achieve both high strength of the base metal and good HAZ toughness, the TMCP technology was applied, and Ceq. was minimized. And to obtain fine HAZ microstructure, fine TiN and Ca(O,S) particles having pinning effect and nucleation site effect were used. Finally, to decrease the formation of brittle martensite-austenite constituent (M-A) in HAZ of multi-pass weld joint, Si content was decreased. By using above technologies, the YS 500MPa class thick steel plate with good weld joint CTOD property have been developed.
Experimental and Numerical Study on Dynamic Response of FSRU-LNGC Side-by-Side Mooring System
Authors: Yue Jingxia , Kang Weili , Mao Wengang , Chen Pengfei , Wang Xi 
Published: November 2019

Abstract
Floating Storage and Regasification Unit (FSRU) becomes one of the most popular equipment in the industry for providing clean energy due to its technical, economic and environmental features. Under the combined loads from wind, wave and current, it is difficult for the prediction of the dynamic response for such FSRU-LNGC (Liquified Natural Gas Carrier) side-by-side mooring system, because of the complicated hydrodynamic interaction between the two floating bodies. In this paper, a non-dimensional damping parameter of the two floating bodies is obtained from a scaled model test. Then the numerical analysis is carried out based on the test results, and the damping lid method is applied to simulate the hydrodynamic interference between floating bodies. The dynamic response of the side-by-side mooring system including six degrees of freedom motion, cable tension and fender force are provided and analyzed. According to the comparisons between numerical results and the test results, it is shown that the proposed coupled analysis model is reliable, and the numerical analysis can properly describe the dynamic response of the multi-floating mooring system in the marine environment. Moreover, the non-dimensional damping parameter which is used in numerical analysis can act as a good reference to the dynamic response analysis of similar multi-floating mooring systems.
Study of Wave Added Resistance and Motions of KCS in Waves With Different Wave Lengths
Authors: Guo Hao , Wan Decheng 
Published: November 2019

Abstract
Estimating added resistance and motions of a ship in waves are essential to predict fuel consumption and speed loss. The added resistance and motions of the 3600 TEU KRISO container ship (KCS) in regular head waves under different wavelengths are investigated using Reynolds-Averaged Navier-Stokes (RANS) method. Volume of Fluid (VOF) method is applied to capture the free surface. The in-house computational fluid dynamics solver, naoe-FOAM-SJTU, is used to compute the added resistance and motions of KCS in regular head waves. Firstly, the first-order Stokes waves in deep water are adopted and generated in naoe-FOAM-SJTU as a numerical wave tank. Secondly, it is presented that the KCS with a Froude number of 0.261 advances in these waves. Regular wave conditions with a wide range of wavelength (0.65 &lt; λ/L &lt; 1.95) are considered. The variations of resistance, pitch and heave show good agreement with experimental results.
To investigate nonlinear behaviors of predicted results, Fast Fourier Transform (FFT) is applied to analyze the results of resistance, heave and pitch with in head wave (μ = 180°). KCS with and without motions is also compared to investigate the relationship between components of resistance and wavelengths. The results of added resistances show that the added resistance of KCS is mainly induced by ship diffraction in short waves. The wave diffraction is not affected by wave frequency. In addition, CFD can accurately calculate the problem on added resistance and ship motions.
ECAs and Lateral Buckling
Authors: Cosham Andrew , Macdonald Kenneth A. , MacRae Ian , Carr Malcolm 
Published: November 2019

Abstract
An engineering critical assessment (ECA) is commonly conducted during the design of an offshore pipeline in order to determine the tolerable size of flaws in the girth welds. API 579-1/ASME FFS-1 2016 and BS 7910:2013+A1:2015 Incorporating Corrigenda Nos. 1 and 2 give guidance on conducting fitness-for-service assessments of cracks and crack-like flaws. DNVGL-RP-F108, 2017 Assessment of flaws in pipeline and riser girth welds describes a methodology to satisfy the fracture and fatigue limit states in DNVGL-ST-F101, 2017 based on Option 2 with ductile tearing in BS 7910:2013. It requires that the stress-strain curve used in a strain-based fracture mechanics analysis should represent a high yield strength combined with low strain-hardening properties (a characteristic high stress-strain curve with low strain hardening), and that used in a stress-based fracture mechanics assessment should represent a low yield strength.
A pipeline operating at high temperatures and/or high pressures is subject to high compressive axial forces. The pipeline might then relieve these forces by buckling. A design that incorporates controlled lateral buckling is an efficient solution to the problem of high compressive axial stresses. Lateral buckling does, however, give rise to relatively high tensile axial strains (possibly exceeding 0.4 percent) in the pipe wall, and, relatively high fatigue loading associated with movement of the buckle under start-up and shut-down cycles.
The calculated tensile axial strain in the pipe wall in a lateral buckle depends on the assumed stress-strain curve. It tends to be higher if a low yield strength combined with low strain-hardening properties is assumed. There is then an apparent inconsistency between the two sets of assumptions.
A deterministic assessment of a circumferentially-orientated, internal surface crack-like flaw in a girth weld in a lateral buckle is used to investigate the significance of this apparent inconsistency.
Development of a Model Predictive Controller for the Wave Energy Converter Control Competition
Authors: Ling Bradley A. 
Published: November 2019

Abstract
The University of Maynooth is hosting a competition to develop a control strategy for a heaving point absorber wave energy converter (WEC). A linear model predictive control (MPC) design for the competition is presented. The state space model used in the MPC was derived numerically from the provided WEC-Sim model using linear system identification methods. A Kalman filter was used as the estimator, while also serving as an unknown input estimator to provide estimates of the excitation force on the WEC. The required excitation force predictions were made using an autoregressive linear prediction model. The inputs to the prediction model included estimated wave excitation forces and measured water surface elevation values from an up-field wave probe. Simulation results of the final control system design are also presented for each of the six wave cases specified by the competition organizers.
The Evolutionary Geometric Physics of Vortex-Induced Vibrations
Authors: Zueck Robert F. 
Published: November 2019

Abstract
Induced vibrations are multi-dimensional oscillations in a marine riser, suspended wire or other slender structures, whereby the maximum amplitude of deflection is generally perpendicular to the sustained action. In previous OMAE papers, we have shown how sustained actions evolve physical changes in slender structures. Using nonlinear physics-based simulations, we showed how these structural changes fundamentally determine the nature of the vibrations that any sustained action (including flowing fluid around the structure) can induce. In this paper, we step back to focus on a classical laboratory experiment, whereby the structure has been constrained to function as a simple mass-on-spring oscillator. In this unchanging structure, we show how the geometric physics of the fluid drag load induce Vortex-Induced Vibrations (VIV). We show how these vibrations naturally grow in time to maximum amplitude.
Time Domain Simulations of Ship Maneuvering and Roll Motion in Regular Waves Based on a Hybrid Method
Authors: Ma Chengqian , Ma Ning , Gu Xiechong 
Published: November 2019

Abstract
Ship maneuvering performance and rolling in waves under complicated environmental conditions are of significant importance for safety and economic reasons. The existing methods for predicting the maneuvering in adverse sea conditions can be categorized into unified two-time scale model, hybrid approach and CFD method. However, traditional potential methods rely tightly on ship viscous force data from test results, and CFD methods of free running ship require large computational resources consumption. In this paper, a 4-DOF (surge, sway, yaw and roll) model based on MMG method considering the wave effect is established to predict the trajectory and rolling motion with better time efficiency.
The 1st order wave force and mean 2nd order drift force in this time-domain model are calculated by the 3D panel method and Cummins impose response function. Instead of model experiments, the hydrodynamic derivatives in the maneuvering model can be calculated by RANS-based numerical simulations of the Planar Motion Mechanism (PMM) test in calm water. Verification for grid convergence is also conducted according to state-of-the-art study. The predicted turning trajectory and rolling angle of the S175 containership in regular waves using CFD results show better agreement with experiment data than empirical formula results. Furthermore, it has been demonstrated that this model is also capable of predicting the ship motion in regular waves with practical accuracy. And the effects of the wave frequency, wave height are investigated consequently base on numerical simulation results.
On Disaster Risk Reduction in Norwegian Oil and Gas Industry Through Life-Cycle Perspective
Authors: Ibrion Michaela , Paltrinieri Nicola , Nejad Amir R. 
Published: November 2019

Abstract
This paper presents the risk reduction in Norwegian oil & gas industry over the time (1975–2016) through a life cycle perspective analysis with the aim to identify the critical stage(s) both in terms of accident occurrence and cause of the accident. Fifteen accidents, major accidents and disasters for example Ecofisk 2/4 Alpha 1975, Alexander L. Kielland 1980, Songa Endurance 2016 were studied. Cases from outside of the Norwegian offshore field — the Piper Alpha 1988, the Bourbon Dolphin 2007, and the Deep Water Horizon 2010 — were also considered as comparison. For each accident and through the life cycle analysis, the occurrence stage of the accident and its main technical causes were identified and compared. It was found that a high risk is concentrated in the Operation (In-Service) stage and associated Marine Operations. Furthermore, it was observed that a high number of accidents in oil and gas industry are associated with mobile structures. All the investigated accidents have acted as powerful reminders to the oil and gas industry that a continuous improvement of risk management and reduction of uncertainty are of paramount importance in order to ensure safe operations and risk reduction for accidents, major accidents and disasters. However, a reactive learning from major accidents and disasters needs to be supported by a proactive learning and development of a dynamic risk culture in the oil and gas industry.
Use of 3D Scan of Weld Joint in Finite Element Analysis and Stochastic Analysis of Hot-Spot Stresses in Tubular Joint for Fatigue Life Estimation
Authors: Larsen Mikkel L. , Arora Vikas , Lützen Marie , Pedersen Ronnie R. , Putnam Eric 
Published: November 2019

Abstract
Several methods for modelling and finite element analysis of tubular welded joints are described in various design codes. These codes provide specific recommendations for modelling of the welded joints, using simple weld geometries. In this paper, experimental hot-spot strain range results from a full-scale automatically welded K-node test are compared to corresponding finite element models. As part of investigating the automatically welded K-joint, 3D scans of the weld surfaces have been made. These scans are included in the FE models to determine the accuracy of the FE models. The results are compared to an FE model with a simple weld geometry based on common offshore design codes and a model without any modelled weld. The results show that the FE model with 3D scanned welds is more accurate than the two simple FE models. As the weld toe location of the 3D scanned weld is difficult to locate precisely in the FE model and as misplacement of strain gauges are possible, stochastic finite element modelling is performed to analyse the resulting probabilistic hot-spot stresses. The results show large standard deviations, showing the necessity to evaluate the hot-spot stress method when using 3D scanned welds.
Study on the Influence of Mesh Grouping on Numerical Simulation Results of Fish Cages
Authors: Huang Liuyi , Li Yuyan , Ni Yi , Cheng Hui , Wang Xinxin , Wang Gang , Zhao Fenfang 
Published: November 2019

Abstract
The Morison Model is widely applied in the numerical simulation for the hydrodynamics assessment of fish cage. In the Morison model, hydrodynamic forces are calculated based on twines. To reduce the computational time, mesh grouping methods (replacement of multiple meshes with less number of equivalent meshes) have been implemented widely in the calculation. However, as the hydrodynamic equation for a mesh is quite different under wave and current, it is not appropriate to use the classical mesh grouping. On the basis of basic hydrodynamic equations of the meshes with current and wave, this paper carried out the study about theoretical analysis of two methods (the equivalent area method and the equivalent volume method) of the mesh grouping, using main parameters of nets such as the diameter, solidity ratio and elastic modulus related to mesh grouping. A single-point mooring cage, of which tension and displacement could be calculated with finite element method, was selected as a case to carry out the verification of two mesh grouping methods. Flume model experiment was used to validate the accuracy of mesh grouping methods. The results indicated that, the equivalent area method has a higher accuracy in the pure current condition, while the equivalent volume method was more accurate in combined waves and current. The accuracy of results using mesh grouping to analyze hydrodynamics of nets within a certain range of grouping times could be insured with an improved calculation speed. This paper can provide practical advice on the mesh grouping process in the numerical simulation of fish cages and fishing gear.
Dented Externally-Pressurised Pipes Subjected to Cyclic Axial Loading
Authors: Chatziioannou Konstantinos , Huang Yuner , Karamanos Spyros A. 
Published: November 2019

Abstract
The present paper describes a numerical investigation of the mechanical response of externally-pressurized dented stainless-steel pipes, subjected to reverse cyclic axial loading. This is the first part of a large-scale project, between The University of Edinburgh and Tianjin University, and is motivated by the mechanical response of offshore pipelines, which are often subjected to cyclic loading during installation or operation. Under those cyclic loading conditions, the pipe may collapse because of accumulation of plastic deformations at the dent area.
The paper describes a numerical simulation of the above physical problem, in an attempt to support experiments on 50mm-diameter stainless steel pipes, which are being performed at the laboratory facilities of Tianjin University. Pipe segments are subjected to reverse cyclic axial loading (tension and compression), in the presence of external pressure. Prior to the application of external pressure and axial load, the pipes are locally dented, in the form of “smooth dent” or “local ovalization”, so that collapse initiates at the dent area. The numerical simulation is aimed at examining some aspects of pipeline behavior to support and complement the experimental observations. The simulation is conducted using rigorous finite element tools, which account for large displacement and nonlinear material. Towards this purpose, an advanced material model is employed, capable of describing the phenomenological aspects of material response under cyclic loading, such as the accumulation of plastic strain and ratcheting.
In the first part of the analysis, the local ovalization (denting) process is simulated. Subsequently, the pipes are subjected to uniform constant external pressure and, keeping the pressure level constant, monotonic or cyclic axial loading is applied until collapse. The numerical results are aimed at identifying the interrelation between the magnitude of the applied loading and the number of loading cycles to failure. The results are presented in diagrams of axial displacement, ovalization and local strain versus the corresponding number of cycles to failure, for specific levels of external pressure.
A Study on Improvement of Fatigue Performance by Shot Blasted Surface Treatment
Authors: Fujii Toshihiro , Gotoh Koji , Deguchi Junichi , Murakami Koji 
Published: November 2019

Abstract
Recently, the strength of the hull structure including fatigue strength has seen significant improvement because of application of IACS CSR (Common Structure rule), developed by IACS. Various methods which can increase the fatigue strength at welded joints are suggested, since the damage morphology on the recently welded structures was observed to be primarily fatigue failure. In Shipbuilding industry, smoothening of the welding bead toe by grinding is the method that is customarily adopted in order to increase fatigue strength. And recently, peening treatment at the welding bead has also been adopted. The peening treatment can reduce stress concentration by smoothening of the welding bead toe, and a compressive residual stress field generated by the impact of peening.
In case of generating compressive residual stress by impact, the same effect could be expected by shot blasting, which is the steel surface treatment before painting.
In this study, the condition of the residual stress generated at welding toe by shot blasting was investigated, and then from results of the fatigue test, the increase in fatigue strength due to residual stress is verified.
Optimization of a Horizontal Axis Tidal Current Turbine by Multi-Objective Optimization
Authors: Nagataki Takumi , Kurokawa Ko , Yamada Reiko , Sakaguchi Daisaku , Kyozuka Yusaku 
Published: November 2019

Abstract
A global search optimization system is applied to the design of a horizontal axis tidal current turbine with shroud. 11 design parameters of the turbine blade and 4 design parameters of the shroud casing are considered for the optimization using a genetic algorithm. In order to reduce the simulation cost, a neural network is applied as the meta-model of the RANS (Reynolds-averaged Navier–Stokes) equation solver. Multi-objectives of the power coefficient at different tip speed ratios are applied to cover a wide operating range of the turbine. The CFD (Computational fluid dynamics) for optimization is validated experimentally for the case of a baseline design, and an optimum design is proposed. In this paper, a static structural analysis has been performed, and its robustness is confirmed under several operating conditions. Furthermore, internal flow of the optimized turbine is discussed in detail. It is found that the optimized blade generates a swirling flow and suppresses flow separation at the diffuser wall. The wide angle of the diffuser successfully achieves a high pressure recovery ratio and results in a high level of suction at the inlet of the turbine. It is found that the high-performance tidal turbine is possible to design if both the blade and the shroud diffuser are optimized at the same time.
Application of the Spectral Nudging on Global Tides Towards a Global Total Water Level Prediction System
Authors: Kodaira Tsubasa , Bernier Natacha , Thompson Keith R. 
Published: November 2019

Abstract
With the long-term goal of developing an ensemble forecast system for coastal flooding, we are developing a dynamically-based, numerical model of the global ocean. The model is based on the NEMO framework and has been used to predict global tides and surges in previous studies. This study focuses on the optimization of the joint prediction of both tides and surges, the two main components of total water level that cause coastal flooding. To improve the predictions of the tide we use a modified form of “spectral nudging”. We show this leads to significant improvements in the prediction of the M2 tide in the open ocean, and also in the shallow regions closer to shore where the model is not nudged. The median value of the vector difference of the tidal amplitude based on sea level observations and a data-assimilative model, and the predictions of our ocean model, is reduced from 11.2 cm to 2.66 cm by the nudging. The improvement deteriorates significantly however if additional tidal constituents are included in the model (most notably S2). This is explained in terms of spectral leakage between tidal bands associated with the nudging methodology and a straightforward solution is proposed.