bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Platform Mounting Orientations on the Long-Term Performance of a Semisubmersible Wind Turbine
Authors: Zhou Shengtao , Li Chao , Xiao Yiqing , Lemmer Frank , Yu Wei , Cheng Po Wen 
Published: November 2019

Abstract
Due to the non-fully-symmetrical configuration, the platform laying angle of semi-submersible floating offshore wind turbines relative to wind/wave load directions has a noticeable influence on the dynamics characteristics of the whole structure, which indicates that the platform mounting orientation should be carefully considered before installation at sea. The directionality effects of short-term wind/wave loads had been discussed in previous studies, which are, however, insufficient to make a full understanding of the directionality impacts. In our study, based on a 25-year met-ocean database, long-term analysis is carried out by means of an efficient frequency-domain model with eight degrees of freedom. The nonlinear quantities such as aerodynamic loads, aerodynamic damping and mooring stiffness are derived from the time-domain simulation tool FAST, serving as a preprocessing database for the frequency-domain model. A case study is carried out by comparing the long-term responses of a Y-shape semi-submersible floating wind turbine in four mounting orientations. Significant differences can be seen. The platform mounted in the most unfavorable orientation tends to suffer from larger peak nacelle acceleration, which would increase the loads and cause higher tower base fatigue damage. These findings highlight the importance of platform mounting orientations and can serve as a basis for the installation of semi-submersible floating wind turbines.
The Influence of Non-Prescriptive Legislation in the Evolution of Offshore Well Integrity Practices: An Exploratory Review
Authors: Morais Carlos H. B. , Abreu Danilo T. M. P. , Santos Joaquim , Maturana Marcos C. , Colombo Danilo , Martins Marcelo R. 
Published: November 2019

Abstract
Among the stochastic tools and risk analysis techniques, ALARP (As Low As Reasonably Practicable) concept has proved to be the most influential guidance regarding the development of regulations and standards of the offshore industry in terms of risk assessment and consequently of equipment integrity. The reasons for that can be traced back to early seventies, when the British Health and Safety Executive (HSE) released its seminal document “The Health and Safety at Work etc. Act 1974”. The 1974 Act was the first regulation to adopt a non-prescriptive approach as a basis to configure the ruling legislation of industrial activities. Since then, risk analysis methods have encountered a vast field of opportunities in the wide range of options proportionated by such framework. In this sense, the Safety Case and the NORSOK standards play a significant role in the non-prescriptive approach application in the offshore industry. The present work discusses the influence of these two frameworks in the definition of the current Brazilian offshore legislation, especially in terms of the design, tests, and monitoring of the so called Solidary Well Barriers throughout the well life cycle. The United States legislation, largely reviewed after the Macondo accident, will be used to counterpoint the prescriptive and non-prescriptive approaches.
Numerical Study on the Temporal Discretization Schemes in Two-Phase Wave Simulation
Authors: Kim Young Jun , Bouscasse Benjamin , Seng Sopheak , Le Touze David 
Published: November 2019

Abstract
The generation and propagation of waves in a viscous flow solver are indispensable part of naval computational fluid dynamic (CFD) applications. This paper presents numerical simulations of two-dimensional wave propagation in the framework of two-phase finite volume method (FVM) with different temporal discretization schemes. Implicit Euler, Crank-Nicolson (CN) and second-order backward temporal discretization schemes are compared by using viscous flow solver based on the open source library OpenFOAM. The combinations of each temporal discretization scheme and explicit limiter are used for the formulation of the Volume Of Fluid (VOF) field convection equation. A new formulation using the second-order backward temporal discretization scheme with explicit limiter are investigated. Two-dimensional periodic domains are considered to compare different time-stepping methods. Also, five different refinement levels of meshes are used to study the convergence properties of each method. The non-linear wave is generated with stream function wave theory using ‘foamStar’, which is a specialized OpenFOAM library package developed by Bureau Veritas in collaboration with École Centrale de Nantes.
Development of a Panel Cutting Method Coupled With an Unsteady Potential Flow Model Based on the Weak-Scatterer Approximation
Authors: Wuillaume Pierre-Yves , Ferrant Pierre , Babarit Aurélien , Lynch Mattias 
Published: November 2019

Abstract
This paper presents a new mesh strategy for unsteady potential flow based solvers. It is based on the coupling between a panel cutting method used for the body mesh and an advance front method to generate the free surface mesh. The goal is to deal with complex geometries for time-domain simulations for marine operations. Firstly, the new mesh generation process is presented in details. Then, two validation tests are presented, using an academic geometry (vertical surface-piercing cylinder) and a complex geometry (FPSO).
A Fracture Mechanics-Based Feasibility Study of Damped Steel Catenary Risers for Pre-Salt Field Developments
Authors: Garmbis Alexandre G. , Zumpano Petrônio , Aguiar Ludimar L. , Brito Raphael M. , Rade Domingos A. 
Published: November 2019

Abstract
In order to enhance competitiveness of rigid risers for the Brazilian pre-salt, great effort has been devoted to study the feasibility of Steel Catenary Risers (SCR) directly connected to Floating Production Storage and Offloading (FPSO) units, where cost savings are expected from the reduction of pipe buoyance modules and overall piping length. A recent paper presented the technical feasibility of Damped SCR, which is a new SCR concept. In that study, some non-field-proven fatigue performance improvements were required, such as girth welds for mechanically lined pipe (MLP) with increased fatigue strength and/or upset end pipes. During the development of this technology, a fracture mechanics approach became essential for the assessment of fatigue and fracture limit state in order to guarantee that the risks associated with fabrication and inspection are within acceptable safety levels. This paper presents the main issues related to fabrication and inspection activities with a particular focus on the smallest critical flaw size. A semi-deterministic Engineering Critical Assessment (ECA) was performed as part of the conceptual design. The uncertainties about input data are discussed and a simplified procedure is proposed. Results are compared with relevant non-destructive testing reliability statistics. This study indicates that the benefits obtained from the use of materials with superior fatigue resistance are limited to the non-destructive testing reliability at some degree. As the proposed methodology deals with uncertainty in input data, a roadmap for the development of a full probabilistic risk assessment of fabrication and inspection feasibility at early design stages is devised.
Controlling Factors of Carcass Fatigue in Unbonded Flexible Pipes
Authors: Fernando Upul S. , Roberts Andrew P. , Davidson Michelle 
Published: November 2019

Abstract
Carcass, the innermost layer of a flexible pipe structure is designed to prevent the collapse of the pressure sheath due to external pressure. Weakness, damage or failure of the carcass layer can result in collapse with associated loss of production and potentially serious risk to pipe integrity and hydrocarbon leakage to the environment. Avoiding carcass failure in service is therefore an essential consideration during the design of unbonded flexible pipes.
Carcass failure is rare in service. This paper highlights the three possible failure modes and presents further analysis on the fatigue failure mode, relevant to dynamic service. Two key features of carcass manufacture are identified as causes for dynamic stress; locking of the carcass profile due to extended pitch and polymer ingress within the carcass cavity.
Guidelines for the design of carcass profiles, setting safe pitch limits and appropriate barrier profile controls to mitigate carcass fatigue failure in dynamic service are presented.
Computational Methods for Moving and Deforming Objects in Extreme Waves
Authors: Veldman Arthur E. P. , Seubers Henk , Hosseini Matin , Chang Xing , Wellens Peter R. , van der Plas Peter , Helder Joop 
Published: November 2019

Abstract
Wave forces can form a serious threat to offshore platforms and ships. The damage produced by these forces of nature jeopardizes their operability as well as the well-being of their crews. Similar remarks apply to coastal defense systems. To develop the knowledge needed to safely design these constructions, in close cooperation with MARIN and the offshore industry the numerical simulation method ComFLOW is being developed. So far, its development was focussed on predicting wave loads (green water, slamming) on fixed structures, and for those applications the method is already being used successfully by the offshore industry. Often, the investigated object (ship, floating platform) is dynamically moving under the influence of these wave forces, and its hydrodynamic loading depends upon the position of the object with respect to the oncoming waves. Predicting the position (and deformation) of the body is an integral part of the (scientific and engineering) problem. The paper will give an overview of the algorithmic developments necessary to describe the above-mentioned physical phenomena. In particular attention will be paid to fluid-solid body and fluid-structure interaction and non-reflecting outflow boundary conditions. Several illustrations including validation, will demonstrate the prediction capabilities of the simulation method.
Fatigue Performance and Crack Growth Assessments of Riser Welds in Mild Sour Environment
Authors: Ghosh Rupak , Aune Robert P. , Popelar Carl F. 
Published: November 2019

Abstract
Fatigue design of deepwater riser system in a sour environment is a challenging task in a project cycle. More often, the challenge is in identifying an appropriate project specific fatigue curve using accurate environmental representation, and establishing a crack growth curve to confirm the acceptance criteria of the welds. Conventional practice in industry is to use a knock down factor (KDF) to capture the effect of corrosion fatigue, rather than taking an effort in executing detailed test/qualification program. A KDF approach can turn out to be very unreliable, specifically, for mild sour environment where significant test data are not available. As a result, there can be several impacts, including delivery of an under-designed system with potential operational risks.
This paper presents comprehensive findings from a sour service qualification program executed in a project cycle. The sour environment is mild, and is slightly above NACE limit (0.1psi ppH2S, pH ∼ 6). The program included a detailed scope of work consisting of in-air and in-environment fatigue test as well as limited scope in understanding fatigue crack growth rate in the same environment. The material used is API 5L X65 seamless pipe with mechanized GMAW girth weld. The results show the unpredictable side of corrosion fatigue, especially in this kind of mild sour environment, which is not well understood.
Wave Effects on the Turning Ability of an Ultra Large Container Ship in Shallow Water
Authors: Tello Ruiz Manases , Mansuy Marc , Donatini Luca , Villagomez Jose , Delefortrie Guillaume , Lataire Evert , Vantorre Marc 
Published: November 2019

Abstract
The influence of waves on ship behaviour can lead to hazardous scenarios which put at risk the ship, the crew and the surroundings. For this reason, investigating the effect of waves on manoeuvring is of relevant interest. Waves may impair the overall manoeuvring performance of ships hence increasing risks such as collisions, which are of critical importance when considering dense traffic around harbour entrances and in unsheltered access channels. These are conditions met by Ultra Large Container Ships (ULCS) when approaching a port, e.g. in the North Sea access channels to the main sea ports of Belgium. Note that due to the large draft of ULCS and the limited water depth, shallow water effects will also influenced the ship. Thus, in such scenarios the combined effects of shallow water and waves on the ship’s manoeuvring need to be studied.
The present work investigates the effect of waves on the turning ability of an ULCS in shallow water. Simulations are carried out using the two time scale approach. The restricted water depth corresponds to 50% Under Keel Clearance (UKC). To gain a better insight on the forces acting on the ship, the propulsion, and the rudder behaviour in waves experimental studies were conducted. These tests were carried out in the Towing Tank for Manoeuvres in Confined Water at Flanders Hydraulics Research (in co-operation with Ghent University) with a scale model of an ULCS. Different wave lengths, wave amplitudes, ships speeds, propeller rates, and rudder angles were tested. The turning ability characteristics obtained from simulations in waves and calm water are presented, and discussed.
Metocean Criteria for the Fatigue Analysis of Subsea Pipelines
Authors: Gibson Richard , Christou Marios 
Published: November 2019

Abstract
This paper is concerned with a methodology for defining metocean criteria for the analysis of subsea pipelines. The approach that has been developed incorporates the statistical dependence between wave and current loading. The method achieves this through a combination of the application of the conditional extreme value model of Heffernan and Tawn (2004) and clustering algorithms. This is particularly important in regions where the currents are largely wind driven as there can be a strong correlation between the two. The results can be used to assess fatigue damage from vortex-induced-vibrations and wave loading. The same model can be used to derive deterministic design events. The method is applied to a pipeline in the Caspian Sea. The results are compared to models that assume either independence or a perfect correlation between waves and currents. It is shown that simpler models that do not accurately model the dependence between the waves and the currents can provide estimates of fatigue damage that are an order of magnitude too high or too low.
Computational Simulation of the Drilling Vessel Motion and its Effects on the Riser/BOP Connection
Authors: Castello Xavier , Párraga Quispe José Luis , Estefen Segen F. , de Souza Marcelo Igor Lourenço , de Moura Jorge Nilo 
Published: November 2019

Abstract
During subsea offshore drilling operations, the floating vessel is connected to the wellhead through a series of equipment assemblies. The riser is exposed to dynamic loads from currents, waves, and drilling platform motions. Therefore, a dynamic analysis of the riser system is required to obtain forces and moments in the wellhead. It is even more important in dynamic positioning (DP) operations, where the knowledge of boundary conditions for a safe emergency disconnection is highly relevant. The objective of this paper is to calculate the effects of changing the light and older BOP (typically with 4 rams) for newer and heavier BOPs (after Macondo accident, with 6 rams) on the Emergency Disconnect Sequence (EDS) time and on wellhead equipment strength. A typical scenario of drilling is proposed, in which the marine riser system considers the drilling string, the lower flex-joint, the marine riser, the kill and choke lines and the tensioners. Tensioners are used to top tension the marine riser and to compensate relative heave motion between the riser and the floating vessel. Riser systems were designed using the API RP 16Q and simulated using Orcaflex software. Vessel dynamic motions were calculated according to the response amplitude operator (RAO) data from a typical offshore drilling semi-submersible. The vessel motion is superimposed by a drift-off motion, which consists of a horizontal displacement along time in the direction of the propagating waves. It is employed to simulate the condition of vessel position loss due to thruster and or control system failure. Results indicate that the use of heavier BOPs reduces significantly the available time for initiating the EDS. Results are worse if older generation of wellhead equipment is used, where a smaller drift-off is necessary to safely disconnect the riser before potential equipment and environmental damage occurs.
The State-of-the-Art in Structural Integrity Management: A Review and Proposed Data-Driven Approach
Authors: Heo YeongAe 
Published: November 2019

Abstract
Probabilistic risk-based approaches have been used for cost-effective structural design and maintenance guidelines. The effectiveness of these provisions, however, has yet to be adequately validated. Also, current risk management approaches are hardly adaptable to changes in operational and environmental conditions as well as structural properties over the service life of structures. As the need and demand of real-time monitoring systems have increased dramatically for high-value and high-risk facilities such as offshore structures particularly, it is important to discuss directions for future research to advance the risk-based management approaches by utilizing the invaluable “big-scale” field data obtained from sensor network systems. Therefore, knowledge gaps in the current state-of-the-art structural risk management approaches are discussed in this paper. Subsequently, a novel risk management framework is presented in this paper integrating physics-based data into a data-driven decision model. The proposed decision framework will improve system adaptability to future performance requirements due to changing operational and environmental conditions and will be applicable to any structural systems instrumented by sophisticated SHM systems such as complex naval and marine systems.
Additives to Enhance Cement Sheath Durability
Authors: Tabatabaei Maryam , Dahi Taleghani Arash , Alem Nasim 
Published: November 2019

Abstract
The primary goal of the oil and gas well cementing is zonal isolation. During the production life of a well, the cement experiences various severe conditions affecting its permeability. These conditions include cracking, debonding, and shear failure which can be worsened by pressure fluctuations during hydraulic fracturing operations. Any of these conditions by forming micro-cracks within the cement or micro-annuli at the casing/cement or cement/rock interfaces create cement permeabilities far beyond the intrinsic permeability of the intact cement sheath. Recently, some studies have been devoted to improving the overall mechanical behavior of the cement by adding carbon nanotubes and carbon nano-fibers. Although these nano-additives offer considerably high strength and modulus, the high costs of these materials persuade us to find alternatives at relatively low costs, such as, graphite nanoplatelets (GNPs). Our preliminary laboratory studies show the effectiveness of GNPs in the enhancement of durability characteristics of the prepared nanocomposite cement paste by improving its compressive strength, ductility and toughness resistance. Considering the importance of dispersion of nanoadditives within the cementitious matrix, we physically or chemically manipulate the surface properties of GNPs to prevent the agglomeration of nanoparticles.
Trend of Utilization of Ocean Space According to Structural Form of Oceanic Architectures
Authors: Sugahara Ryo , Kuroyanagi Akio 
Published: November 2019

Abstract
The aims of this research are to understand the construction history, subsequent refurbishment, and use of existing oceanic architectures and to clarify the establishment cause, location, and facility use of oceanic architectures, from which the current state of the oceanic buildings and propose new ways of using maritime areas in the future may be recognized.
First, a wide variety of facilities of oceanic architectures have been built all over Japan in line with economic growth since 1960. However, in the 2000s as public interest in oceanic architectures become sluggish, many facilities have been forced to close. After these circumstances, the use of marine areas has been recognized again in recent years, and the interest in oceanic architectures has been reintroduced.
For the survey method, existing examples using aerial photographs are confirmed and the operation status of the facilities are clarified. Based on this, we selected ten study subjects. We carried out on-site survey at the target facilities and conducted interview survey to local governments, facility owners, and other concerned parties. In addition, relevant design books and materials are collected, and facility outline, construction history, usage trends, and the surrounding locations are studied.
As a result, it was confirmed that oceanic architectures are closely related to the surrounding seas. In addition, it was confirmed that oceanic architectures have a certain base as regional entities, and increasing the usefulness of facilities can be achieved by acquiring new added values through continuous use of the maritime area.
Effect of Non-Gaussian Distribution of Fully-Nonlinear Waves on Offshore Platform Motion Responses
Authors: Baquet Aldric , Lim Ho-Joon , Kim Jang Whan 
Published: November 2019

Abstract
In this paper, we focus on the effect of the non-Gaussian distribution in the fully-nonlinear wave on offshore platform response. The motion responses of two kinds of floating platforms are investigated numerically using a conventional time domain program. The input wave is generated using two methods. In the first method, linear wave components with randomly distributed wave phases are used as input in the time domain software as it is usually done in the global performance analysis during offshore projects. In the second method, the wave components come from a nonlinear irregular wave simulation using a potential numerical wave tank (PNWT). For both cases, twenty realizations of 3-hour duration are performed and the ocean wave is described by a JONSWAP spectrum. Then the response spectra, the probability distributions and the extreme responses of the platform motions and air gaps are compared.