bluuebunny/crossref_metadata_2025_split huggingface dataset:
Calculation of the Dynamic Positioning Capability of an Offshore Wind Farm Vessel During the Jack-Up Process in the Early Design Stage
Authors: Liebert Maximilian 
Published: November 2019

Abstract
As a consequence of the planned exit from fossil-based energy in the European Union the exploitation of renewable energies has become a major aspect of the Offshore Industry. Especially the construction and operation of offshore wind energy turbines pose a challenge which is met by the use of jack-up vessels with extendible legs. In order to dimension the vessel’s manoeuvring devices in the early design stage and to ensure a safe jack-up process for given environmental loads the dynamic positioning capability during the jacking including the influence of the legs has to be calculated. As part of the development of a holistic dynamic analysis this paper presents the implementation of the legs’ influence in an existing manoeuvring method. The manoeuvring method solves the equations of motion in three degrees of freedom (surge, sway, yaw). It is based on a force model which comprises various modular components. Therefore another component for the leg-forces is added. A Morison approach is chosen to calculate the hydrodynamic forces on the cylindrical legs. The legs’ hydrodynamic added masses are accounted for and added to the hull’s inertial terms. The benefit of the presented method is the possibility to calculate the dynamic positioning capability with extended legs without being dependent on the results of either time-consuming or non-specific model tests. Therefore the method represents a fast computing tool to design the vessel for the specific environmental conditions of the site of operation.
The Impact of Climate Change on the Long-Term Response of Offshore Structures: A Study Case
Authors: Mosquera Irvin Alberto , Sagrilo Luis Volnei Sudati , Videiro Paulo Maurício 
Published: November 2019

Abstract
This paper discusses the influence of the climate change in the long-term response of offshore structures. The case studied is a linear single-degree-of-freedom (SDOF) system under environmental load wave characterized by the JONSWAP spectrum. The wave parameter data used in the analyses were obtained from running the wind wave WaveWatch III with wind field input data derived from two Global Climate Models (GCMs): HadGEM2-ES and MRI-CGCM3 considering historical and future greenhouse emissions scenarios. The study was carried out for two locations: one in the North Atlantic and the other in Brazilian South East Coast.
Environmental contours have been used to estimate the extreme long-term response. The results suggest that climate change would affect the structure response and its impact is highly depend on the structure location, the global climate model and the greenhouse emissions scenario selected.
Qualification of Thermoplastic Composite Pipe Risers: Combined Pressure and Bending Loading
Authors: Bahtui Ali , Kidykas Karl , Richardson Joshua , Wilkins Jonathan 
Published: November 2019

Abstract
In offshore ultra-deepwater oil fields, weight and cost reduction is one of the operators’ top priorities, while maintaining safety and reliability standards. These challenges have made conventional flexible risers a less favourable choice for new construction and replacement projects and have forced asset owners to explore cost saving through innovative technologies such as Thermoplastic Composite Pipe (TCP). Magma Global’s light weight m-pipe® TCP riser and flowline product offers over 40% reduction in installed riser project costs, while bringing exceptional permeation, corrosion, high-temperature and fatigue performance and most importantly long-term reusability benefits. This product is the subject of a thorough qualification program in agreement with the requirements of operators and independent verification agents (IVA) to demonstrate the product’s safety and reliability to asset owners and local regulatory bodies.
This paper presents recent developments on the qualification campaign of m-pipe® TCP for riser applications, with a focus on combined pressure and bending tests designed to verify the pipe strength and stiffness. It addresses the product’s ability to withstand loading in the riser touch-down region of a Free Hanging Catenary (FHC). The qualification process of sample manufacture, rig setup, instrumentation & testing, design model development and validation is presented. Burst load cases and combined bend & burst load cases are tested on m-pipe® and results are compared against design model predictions. We hope the paper will be of interest to anyone working in new material development or product qualification in the offshore industry.
Comparison of VOS and ERA-Interim Wave Data
Authors: Vettor Roberto , Guedes Soares C. 
Published: November 2019

Abstract
Accuracy of Voluntary Observing Ship’s reports is evaluated by a one-to-one comparison with ERA-interim database, specifically considering significant wave height. A first screening allows to detect the most common and undeniable mistakes, as for instance clear errors in reporting the position of the vessel, and delete these observations. Moreover, previous literature is considered to remove systematic biases. Then each report is matched with the appropriate numerical data in terms of location and time, in order to evaluate the scattering of the data, to identify the outliers, and to further prune the database. The procedure allows not only to maintain a database clean from clearly wrong information, which can compromise the statistics, but also to recognize areas and conditions in which the mismatch between numerical data and observations is critical, eventually speculating on the motivations.
Comparison of Temporal and Spatial Statistics of Nonlinear Waves
Authors: Bitner-Gregersen Elzbieta M. , Gramstad Odin 
Published: November 2019

Abstract
In the past, it was most common to derive wave parameters and their statistics from time series of wave elevation. The duration of the wave records has been usually restricted to 20 or 30 minutes. Recently, increasing attention has started to be given to spatial wave data and wave statistics, particularly due to introduction in oceanography of stereo camera systems for collecting space–time ensemble of sea surface elevation. Using numerical linear, 2nd and 3rd order simulations this study compares temporal and spatial statistics of wave parameters. The 3rd order wave data are simulated by a numerical solver based on the Higher Order Spectral Method (HOSM) which includes the leading order nonlinear dynamical effects, accounting for the effect of modulational instability. The Pierson-Moskowitz and the JONSWAP spectrum with different gamma parameters are used in the analysis. Sea states with wave steepness where rogue waves were recorded in nature are considered. Consequences of using temporal contra spatial statistics are discussed in perspective of marine structures’ design. Functional dependency between wave parameters characterizing occurrence of rogue waves in unidirectional wave field is proposed.
Simplifying Methods for Fatigue Analysis of Risers
Authors: Pereira Luiz O. C. M. , Videiro Paulo M. , Sagrilo Luís V. S. 
Published: November 2019

Abstract
This work presents methods for reducing computational costs to estimate fatigue damage in riser structures by simplifying the sea state matrix to be solved in time domain by finite element analyses. Two different methods are proposed: The Equivalent Damage Method (EDM), which is a lump block method with an innovative formulation using vessel linearized response to determine significant sea states; and the Response Surface Method (RSM), which uses results from a few sea states to estimate results for other intermediary scenarios required for the fatigue analysis. Basic assumptions and guidance on how to apply the proposed methods are explained through the text.
The methods are used to solve an example of a Steel Catenary Riser (SCR) connected to a Semi-Submersible vessel, resulting in a reduction of almost 80% of the required computing time. Results show accurate values for damage estimates at the top of the riser, and limitations at the touch down zone. Advantages and disadvantages of each method are discussed in detail, demonstrating that they can be used with discretion at early design stages to estimate fatigue damage of risers, umbilicals and mooring lines in general.
Development and Validation of CFD Analysis Procedure for Predicting Wind Load on Commercial Ships
Authors: Lee Sang-Hun , Kim Sei-Hwan , Kim Deok-Su , Lee Young-Bum 
Published: November 2019

Abstract
This paper describes a numerical procedure for the prediction of the wind load on various types of commercial ships, such as LNGC, oil tanker and container ship. As the size of vessels increases, wind load is playing a more important role when sailing in an open sea and mooring at harbors. To estimate wind load, 3D steady RANS CFD simulation is performed and validated with experimental results obtained from wind tunnel tests. The effect of turbulence source is studied to maintain the turbulence intensity profile at the test section of the wind tunnel and the boundary layer mesh is also investigated to improve the accuracy. The discrepancy in force and moment coefficients between CFD results and wind tunnel tests is reduced and the comparison results show good agreements.
Motion and Load Prediction of Floating Platform in South China Sea Using Deep Learning and Prototype Monitoring Information
Authors: Yao Ji , Wu Wen-hua , Zhao Zi-shu 
Published: November 2019

Abstract
The offshore floating platform shows the strong nonlinear characteristics subject to harsh ocean environmental conditions. It is of practical significance and engineering value to predict the marine environmental load and platform motion response by using the prototype monitoring information. Meanwhile, under the interaction of the high-frequency six degrees of freedom (DOF) movements of the platform.
Based on the long-term prototype monitoring data of a semi-submersible platform in the South China Sea, the present paper mainly studies the following two aspects:
1.The prediction of ocean environmental load considering time correlation is studied based on the method of long-short-term memory (LSTM) neural network with the combination of the field monitoring data. The comparison between predicted and measured results shows that the present prediction method has the high accuracy and low computation cost. Besides, this method can be extended to short-term predictions of other environmental loads.
2.The nonlinear mapping relationship between the ocean environment load and the floater motions is constructed based on the deep learning method. The simulated results indicated that the mapping relationship can be used to predict the six DOFs motions of the platform with high accuracy by using the forecasting prototype monitoring data and ocean weather information. Based on this research and the short-term prediction of environmental loads, we can do some studies on short-term prediction of floater motions in the future.
UHB Design Approach for Multiple Pipelines Installed in Shared Trench
Authors: Liu M. , Cross C. 
Published: November 2019

Abstract
Upheaval buckling (UHB) mitigation for trenched and buried pipelines can constitute a substantial cost element for offshore field development. There appears to have a variety of reasons for dual or more pipelines and umbilicals to be considered for installation inside the same trench. A single shared trench has been used for multiple pipelines not only for cost saving, but especially when constrained and driven by route corridor challenges. The common practice for dual pipeline trenching and UHB design is to either perform UHB design independently without due consideration of the pipelines in the proximity, potentially resulting in a compromised UHB mitigation design, or simply combine the uplift resistance required for each individual pipeline in the proximity to obtain the overall backfill/rock dumping to account for pipeline interactions.
This paper re-examines the rationale of the normal practice and some fundamental aspects of UHB design for dual pipelines installation inside the same trench. The proximity effect on the uplift resistance is investigated with respect to pipeline spacing and burial depth. Its impact on the UHB mitigation is considered by a detailed analysis and a series of parametric simulations with respect to pipeline dimensions and gaps. The sensitivity of the soil slip failure angle and the dilatancy is also performed.
Based on the theoretical analysis and FEA modelling, a model solution is formulated and proposed for evaluating uplift resistance reduction for multiple lines. The formulae are extended to deal with multi-layered soil and rockdump. A number of pipeline configurations have been discussed including a piggyback arrangement. A robust UHB mitigation and reduced optimum rockdumping can be achieved by considering the proximity effect through challenging the industry norms and common approach.
Recent Developments and Challenges of Cleavage Fracture Modelling in Steels: Aspects on Microstructural Mechanics and Local Approach Methods
Authors: Jiang Quanxin , Bertolo V. M. , Popovich V. A. , Walters Carey L. 
Published: November 2019

Abstract
Offshore activity in low-temperature areas requires the use of analysis methods that are capable of reliably predicting cleavage (brittle) fracture of ferritic steels in order to guarantee the structural integrity during service. Cleavage fracture is controlled by physical events at different size scales and is influenced by the multiple microstructural parameters of the material. The prediction of fracture toughness of steels based on the microstructure has received great attention, and relevant techniques have been continuously developed. This paper is aimed at reviewing the recent development of cleavage fracture modelling in steels and identifying the existing challenges to inspire further research. The paper contains three parts aimed at explaining how methods are developed and utilized to predict fracture toughness of steel from its microstructures. (1) The complex multiparametric nature of the microstructures of ferritic steels and its influence on cleavage fracture is introduced. (2) A review is given on the main perspectives and models in micromechanisms of cleavage fracture in steels. (3) Discussion is contributed to the link between micromechanisms and the local approach in cleavage fracture modelling. As a result, the paper gives a state of the art on microstructural mechanics and local approach methods of cleavage fracture modelling in structural steels.
Tethered BOP Stacks: Performance and Monitoring
Authors: Killbourn Stuart , Kebadze Elizbar B. , Maher James 
Published: November 2019

Abstract
Subsea wells present challenges for fatigue utilisation throughout the life of these high-value assets. New wells may be constructed at seabed locations where soil properties may be unfavourable or uncertain. Existing wells may require workover and eventual abandonment. This can lead to relatively small conductors supporting higher BOP masses than was envisaged when these wells were constructed. To address such stability issues during drilling and work-over operations, a BOP stack may be tethered to seabed anchors to provide lateral retention. The increased foundation stiffness raises the BOP characteristic frequency which suppresses motion of the BOP and significantly reduces fatigue of the conductor and wellhead. Real-time monitoring of the tether tensions and BOP characteristic frequency provide on-going verification of the efficacy of this fatigue suppressing technology as well as tracking structural integrity. For example, the ability of the monitoring system to detect loss of tether tension and the success of ROV intervention to reapply tension is demonstrated.
Numerical Study on Vortex Induced Motion of Circular Cylinder With Low Aspect Ratio in Currents
Authors: He Jiawei , Wan Decheng 
Published: November 2019

Abstract
This paper presents the investigation results of the VIM phenomenon, discloses the characteristics of the relative motions of a floating cylinder. Floating circular platforms present a large characteristic diameter associated with a large natural period of motions in the horizontal plane. In this paper, the VIM around floating circular cylinders, m* = 1.0, with very low aspect ratio, L/D = 2, as a motivation for better understanding the VIM of Spar platforms.
In order to study vortex induced motions (VIM) response of a circular cylinder, numerical computations are carried out by our in-house VIM solver vim-FOAM-SJTU. In the CFD simulations the cylinder is moored with linear springs to provide a range of reduced velocities. The fluid domain is gridded by an unstructured grid. The boundary layer is modeled with a first boundary layer y+≈2. The focus is on the effect of reduced velocity on the VIM response. Free decay tests and vortex-induced motion (VIM) tests have been built numerically. The Fourier analysis of the motions have been performed in order to explain in figure-eight-type motion trajectory.
Design Optimization of Ship’s Bow Sailing in Kara Sea and Barents Sea
Authors: Liu Jianfei , Feng Guoqing , Ren Huilong , Hu Wenjia , Sun Yuwei 
Published: November 2019

Abstract
Ships performing their missions in the polar regions will inevitably suffer from sea ice collision, which will lead to structural safety problems. Therefore, ships should be designed according to the characteristics of polar sea ice to enable them to navigate safely in the polar regions. Based on the probability density curve of sea ice thickness and the occurrence frequency of sea ices of different sizes of the Kara Sea and the Barents Sea, this paper preliminarily designs ship’s bow sailing in the Kara Sea and the Barents Sea, establishes the ship’s bow-ice collision model and carries out numerical simulation to obtain the stress distribution. Then it optimizes the structure of the parts of the ship’s bow. After the optimization, the bow structure meets the strength requirements and the weight of the ship’s bow is relatively light.
Hydrodynamics Around a Deep-Draft Semi-Submersible With Biomimetic Tubercle Corner Design
Authors: Liang Yibo , Shi Weichao , Tao Longbin 
Published: November 2019

Abstract
Leading-edge tubercles have been investigating widely on the performance of foils in the last decade. In this study, the biomimetic tubercle design has been applied to the corner shape on a deep-draft semi-submersible. A numerical study on flow over a deep-draft semi-submersible (DDS) with a biomimetic tubercle corner shape was carried out to investigate the corner shape effects on the overall hydrodynamics and motion responses. The hydrodynamic performance of the biomimetic tubercle corner is compared with a traditional round corner design platform. It is demonstrated that, as the corner shape design changed, the motion responses alter drastically. In addition, the flow patterns were examined to reveal some insights into fluid physics due to the biomimetic tubercle corner design. The comprehensive numerical results showed that the three-dimensional effect, which causes spanwise flow, can be reduced by a continuous spanwise (column-wise) variation of the shear-layer separation points.
Robust Leakage Modeling for Plug and Abandonment Applications
Authors: Al Ramadan Mustafa , Salehi Saeed , Teodoriu Catalin 
Published: November 2019

Abstract
Oil and gas wells that require to be shut off forever, after depleting their reserves, need to be plugged and abandoned. Plug and Abandonment (P&A) operations induce many arduous challenges worldwide. The aim of P&A is to isolate and prevent fluid leakage in the wellbore in such a way that all fluids are contained in their formation for an undefined time. Failure of P&A in isolating and preventing fluid leakage can jeopardize the well integrity. Cement plugs that are used in this operation play a crucial role in maintaining the well integrity.
Cement is considered as a porous medium that has an ultra-low permeability that can be achieved when some additives are used in the cement slurry to reduce its permeability and pore space. The cement plug may deteriorate with time under harsh downhole conditions, such as high pressure and temperature and exposure to different fluids. Cement plug deterioration will result in increasing the cement permeability or the overall permeability by creating channels or microannuli.
In this study, several scenarios are presented for gas leakage through cement plugs. In these leakage scenarios, the differential pressure across the cement plug was varied. The aim of generating these scenarios is to investigate the current required cement plug length. In each scenario, four different permeability values were used to assess the risk associated with each value. In addition, the cement plug length was varied to investigate how the cement plug length is going to help ensure good well integrity.
The leakage scenarios presented revealed that longer cement plugs have a longer leakage time. In addition, the results show an increase of leakage time as microannulus gap permeability decreases. Differential pressure exerted on the cement plug have a strong effect on the leakage time. To achieve a long term well integrity in P&A phase, an ultra-low permeable cement plug with excellent bonding, longer cement plug, and a lower differential pressure across the cement must be considered.
Learning a Predictionless Resonating Controller for Wave Energy Converters
Authors: Shi Shuo , Patton Ron J. , Abdelrahman Mustafa , Liu Yanhua 
Published: November 2019

Abstract
This article presents a data-efficient learning approach for the complex-conjugate control of a wave energy point absorber. Particularly, the Bayesian Optimization algorithm is adopted for maximizing the extracted energy from sea waves subject to physical constraints. The algorithm learns the optimal coefficients of the causal controller. The simulation model of a Wavestar Wave Energy Converter (WEC) is selected to validate the control strategy for both the regular and irregular waves. The results indicate the efficiency and feasibility of the proposed control system. Less than 20 function evaluations are required to converge towards the optimal performance of each sea state. Additionally, this model-free controller can adapt to variations in the real sea state and be insensitive and robust to the WEC modeling bias.
Influence of Lined Pipe Fabrication on Liner Wrinkling
Authors: Gavriilidis Ilias , Karamanos Spyros A. 
Published: November 2019

Abstract
An economical method to protect offshore pipelines against corrosive ingredients of hydrocarbons is a double-walled (also called “lined” or “bi-metallic”) pipe, in which a thick-walled low-alloy carbon steel (“outer pipe”) is lined internally with a thin layer (“liner pipe”) from a corrosion resistant alloy material. During the deep-water installation, a lined pipe is subjected to severe plastic loading, which may result in detachment of the liner pipe from the outer pipe forming short-wave wrinkles, followed by local buckling. In the current study, alternative lined pipe manufacturing processes are investigated, including elastic, plastic hydraulic and thermo-hydraulic expansion of the outer pipe, for different initial gaps between the two pipes. The problem is solved numerically, accounting for geometric non-linearities, local buckling phenomena and elastic-plastic material behaviour for both the liner and outer pipe. Two types of numerical models are developed, a quasi-two-dimensional model, examining the mechanical bonding between the pipes, and a three-dimensional model, repeating the manufacturing process and investigating its effect on the mechanical behaviour of a lined pipe subjected to monotonic bending. In addition, the influence of initial geometric imperfections on liner pipe buckling is investigated, showing the imperfection sensitivity of the lined pipe bending behaviour, for each fabrication process.