bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electromagnetic, Mechanical and Manufacturing Properties for Cable Wound Direct-Drive PM Linear Generators for Offshore Environments
Authors: Hultman Erik , Ekergård Boel , Leijon Mats 
Published: August 2013

Renewable energy conversion in offshore environments, such as wave, wind and tidal energy, can potentially give a considerable contribution to the global electric energy demand. These harsh environments require robust generators with minimal need for maintenance at competitive costs. To reduce the generator cost, the electromagnetic design must be done with manufacturing in mind. An optimal design provides high electric efficiency, long device life-time, little need for maintenance and low manufacturing costs.
Modern simulation tools can be used to optimize the electromagnetic design of a generator for a specific task and operation mode. Hereby both electromagnetic losses and material stresses can be reduced. Industrial robots might provide new possibilities to automate generator-specific manufacturing tasks.
A generator design with a cable wound stator, surface mounted permanent magnets on the translator and direct-drive linear technology is investigated in this article. This concept has a simpler and more robust mechanical design, while both the electromagnetic losses and the need for maintenance are reduced. By reducing the number of generator assembly steps, manufacturing might also be facilitated. Further work is however needed in developing automated assembly methods and comparing them to conventional generator manufacturing.
Study of a Floating Foundation for Wind Turbines
Authors: Gueydon Sébastien , Weller Sam 
Published: August 2013

Offshore wind farms are currently located predominantly in shallow water as it is possible to cost effectively install bottom fixed offshore turbines. Where shallow water sites are not available, floating offshore turbines could be a better solution than bottom fixed turbines.
Currently three main concepts are promoted for the design of a floating wind turbine: a ballast stabilized floater (i.e. spar), a buoyancy stabilized floater (i.e. barge or semi-submersible) or a mooring stabilized floater (tension leg platform). In April 2011 the DeepCWind consortium visited MARIN to carry out model tests in the offshore wave basin with these three types of floating wind turbine platform.
This paper reports a numerical study of a wind turbine supported by a semi-submersible floater. The response of the floating system to wind and wave conditions is compared to physical measurements at 1:50 model scale. The outcome of these comparisons is discussed in the conclusions of this paper.
Development of Fixed Hydrodynamic Lifting Surfaces to Stabilise Anchoring Structures in Energetic Tidal Flows
Authors: Harding Samuel F. , Bryden Ian G. 
Published: August 2013

This paper presents the research currently being carried out on the potential contribution of hydrofoils to generate additional down-force on seabed fastenings in energetic tidal flows.
Firstly, the dynamic lift of a hydrofoil subjected to vertical velocity perturbations was analyzed numerically, showing the reduced response to the fluctuation when unsteady aerodynamic theories are introduced. Secondly, an experimental set-up was developed for the deterministic generation of two-dimension velocity perturbations in a recirculating water flume. This will allow the combined effect of vertical and longitudinal velocity fluctuations on the lift force to be measured.
The Effect of the Spectral Distribution of Wave Energy on the Performance of a Bottom Hinged Flap Type Wave Energy Converter
Authors: Clabby D. , Henry A. , Folley M. , Whittaker T. 
Published: August 2013

The power output from a wave energy converter is typically predicted using experimental and/or numerical modelling techniques. In order to yield meaningful results the relevant characteristics of the device, together with those of the wave climate must be modelled with sufficient accuracy.
The wave climate is commonly described using a scatter table of sea states defined according to parameters related to wave height and period. These sea states are traditionally modelled with the spectral distribution of energy defined according to some empirical formulation. Since the response of most wave energy converters vary at different frequencies of excitation, their performance in a particular sea state may be expected to depend on the choice of spectral shape employed rather than simply the spectral parameters. Estimates of energy production may therefore be affected if the spectral distribution of wave energy at the deployment site is not well modelled. Furthermore, validation of the model may be affected by differences between the observed full scale spectral energy distribution and the spectrum used to model it.
This paper investigates the sensitivity of the performance of a bottom hinged flap type wave energy converter to the spectral energy distribution of the incident waves. This is investigated experimentally using a 1:20 scale model of Aquamarine Power’s Oyster wave energy converter, a bottom hinged flap type device situated at the European Marine Energy Centre (EMEC) in approximately 13m water depth. The performance of the model is tested in sea states defined according to the same wave height and period parameters but adhering to different spectral energy distributions.
The results of these tests show that power capture is reduced with increasing spectral bandwidth. This result is explored with consideration of the spectral response of the device in irregular wave conditions. The implications of this result are discussed in the context of validation of the model against particular prototype data sets and estimation of annual energy production.
The Evolution of Lazy-S Flexible Riser Configuration Design for Harsh Environments
Authors: Anderson Keith , O’Connor Mark 
Published: August 2013

Flexible riser configurations in harsh environments require riser buoyancy in order to decouple vessel induced motions from the seabed interface. This is achieved through either wave (distributed buoyancy) or S (subsea buoy) solutions.
In the UK sector of the North Sea circa 30% of all floating production system field developments utilise subsea buoys in Lazy-S configurations. The majority of these fields have been in service for many years and designed prior to the widespread adoption of current industry standards, the analytical rigour available today, and better characterisation of the metocean environment. In many cases original system design has also been for 50yr return period conditions, compared to the specified 100yr return period events required in todays codes and standards, e.g. ISO 13628-2 [1].
Therefore, when replacement riser or life extension work is performed on existing structures or new developments are being designed there can be significant challenges in confirming the applicability of traditional system configuration designs.
The principal challenges with these configurations is minimising sag bend compressions driven by differential buoy vs. vessel motions and maintaining the riser or umbilical minimum curvature and compression criteria at the seabed touch down. The latter point is a particular problem for umbilicals routed via Lazy-S configurations owing to their relatively low weight and stiffness, and constraining MBR criteria.
This paper considers the applicability of Lazy-S configurations as a solution to modern harsh environment field developments and the evolution in Lazy-S system design to address the design challenges with particular emphasis on the TDP response.
Comparison of Different Equivalent Design Waves With Spectral Analysis
Authors: de Hauteclocque Guillaume , Derbanne Quentin , El-Gharbaoui Amine 
Published: August 2013

Design waves are widely used to assess stress in vessels. Compared to a full spectral analysis, this method reduces the number of required structural calculations and is expected to provide similar results. Moreover in a rule context, it allows loading a structural model with a simplified hydrodynamic loading, via explicit formulae for extreme hydrodynamic loads and associated load combination factors (LCF).
In a broad sense, an equivalent design wave (EDW) is a wave on which a selected response is equal to a target value (generally the spectral extreme response). If general practice is to define the EDW as a regular wave, it is possible to define it more realistically; there are also different ways to define heading and period of the EDW which can lead to significantly different results. In this paper the EDW are not restricted to regular waves: response conditioned waves (RCW) and directional response conditioned waves (DRCW) are also investigated. Those waves include more physics and are shown to overcome some of the inconsistencies of the regular wave (Load Combination Factor above 1 for instance).
The different methods are then applied to an FSRU; hydro-structure calculations are carried out, the resulting stress is calculated in more than 2000 relevant elements. The way to select a few design waves among a lot of individual loads from the hydro-dynamic calculation (motion, acceleration, internal loads, pressure) is discussed and finally, the stress computed by the different design waves is compared to the direct spectral calculation.
On Pipeline Lateral Buckling: Lessons Learned and Current Design Challenges
Authors: Maschner Emil A. , Abdalla Basel 
Published: August 2013

The subject of lateral buckling design in recent years has by necessity become increasingly more involved as pipeline projects have moved into more difficult environments where there is a need for optimized economic solutions with assured through-life reliability.
The authors have had direct design responsibility and specialist involvement with a large number of projects covering a diverse range of environments, single or PIP systems, variable product characteristics and operating conditions, external applied loading type, and geographical installation limitations. These include shallow and deep water, large thin walled and small thick walled diameter pipes, flat to undulating hard to soft seabed, variable cohesive and non-cohesive surficial soil types and various other project considerations which have impacted on the chosen design solution.
The purpose of this paper will be to highlight aspects of global buckling design associated with reliable in place systems and conversely those aspects associated with integrity risks to the as-laid operational pipelines. A review of past project challenges along with a commentary as to the state of the art at the time gives an opportunity to evaluate risks and challenges being faced on current projects. Particularly, as it seeks to develop ever more cost effective designs with proven robustness but optimized safety margins for the installation and operation of HT/HP pipelines in marginal fields.
Underwater Stress Relief and Fatigue Improvement by Ultrasonic Peening
Authors: Kleiman Jacob , Kudryavtsev Yuri , Lugovskoy Alexander 
Published: August 2013

A new ultrasonic peening instrument was developed for underwater treatment of welds and welded structures. The Ultrasonic Peening (UP) established itself as a promising process for fatigue life improvement of welded elements and structures. The beneficial effect of UP is obtained through relieving of harmful tensile residual stresses and introducing of compressive residual stresses into surface layers of materials, and through decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of the surface layers of the materials.
In the design of the underwater UP instrument specially selected anti-corrosion materials are used. The underwater UP instrument can be used for treatment of welds at depths up to 30 meters or, if required, with certain modifications, even deeper. Acoustic pump principle is used in the originally developed system for water cooling of the transducer. The developed UP system allows for improvement treatments at four different power levels and is using replaceable working heads that come in various configurations with variable numbers of pins, depending on the application.
Offshore Platform Fluid Structure Interaction Simulation
Authors: Marzban Ali , Lakshmiraju Murthy , Richardson Nigel , Henneke Mike , Wu Guangyu , Vargas Pedro M. , Oakley Owen 
Published: August 2013

In this study a one-way coupled fluid-structure interaction (FSI) between ocean waves and a simplified offshore platform deck structure was modeled. The FSI model consists of a Volume of Fluid (VOF) based hydrodynamics model, a structural model and an interface to synchronize data between these two.
A Computational Fluid Dynamics (CFD) analysis was used to capture the breaking wave and impact behavior of the fluid on the structure using commercially available software STAR-CCM+. A 3D Finite Element (FE) model of the platform deck developed in ABAQUS was used to determine the deflection of the structure due to hydrodynamic loads. Nonlinear material behavior was used for all structural parts in the FE model. Transient dynamic structural analysis and CFD analysis were coupled by transferring the CFD-predicted pressure distribution to the structural part in each time step using the co-simulation capabilities of STAR-CCM+ and ABAQUS. The one-way FSI model was applied to investigate the possible physical causes of observed wave damage of an offshore platform deck during a hurricane. It was demonstrated that with proper physical conditions/configurations, the FSI model could reproduce a structural deformation comparable to field measurement and provide valuable insight for forensic analysis.
Predictions of Armour Wire Buckling for a Flexible Pipe Under Compression, Bending and External Pressure Loading
Authors: Sertã Otávio , Fumis Rafael , Connaire Adrian , Smyth John , Tanaka Rafael , Barbosa Teofilo , Godinho Carlos 
Published: August 2013

During installation and operation a flexible pipe may be subjected to high compressive forces, high cyclic curvatures and external pressures leading to high reverse end-cap loads. Under such loading conditions, which occur particularly in the touchdown region for deep water applications, the limiting condition for the flexible pipe can be the compressive stability of the tensile armour wires. Two potential instability modes are possible: radial mode (birdcaging) and lateral mode (lateral wire disorganization). Previous work on the subject has established the key factors which influence the onset of each buckling mode [1],[2],[3] and [4].
In order to ensure the feasibility of flexible designs for applications with increasing water depth, it is important to improve the knowledge of the mechanisms which can lead to instability of armour wires and enhance the ability to predict with greater assurance, the particular conditions which increase the risk of wire instability.
The focus of this work is the comparison of finite element prediction of radial buckling (birdcaging) with physical testing results under loading states that lead a pipe to birdcaging failure.
The numerical model incorporates all tensile armor wires and their interactions with each other and adjacent layers. The outer sheath and reinforcing tape layers are explicitly represented, while the inner layers of the pipe (pressure armour and carcass sheath) are idealized using a homogeneous representation. The model also incorporates the effects of manufacturing pre-tension and hoop strength in the anti-birdcaging tape layers which are critical determinants for the onset of buckling.
A key aspect of the method presented is the means by which the loading is applied. Specifically, the modeling handles the simultaneous and controlled application of end rotations, axial compression and radial resistance of the tapes through to the point of tape failure, pipe ovalisation and subsequent radial displacement and buckling of individual wires.
In summary, in this paper a solid modeling approach is presented, which is compared with full a scale sample test data, that enables the simulation of a flexible pipe undergoing large combined compression, curvatures and pressure loading.
SCR Fatigue Feasibility Prediction for Deepwater FPSO Applications
Authors: Xiang Sherry , Cao Peimin 
Published: August 2013

Many of the recent offshore oil and gas discoveries in the world have occurred in deep waters, at locations far away from the existing subsea infrastructure. Floating Production Storage and Offloading systems (FPSOs) are the preferred field development solutions for those locations with mild and moderate environments. The simplest fluid transfer system between the seabed and the FPSO is a simple catenary configuration, with Steel Catenary Risers (SCRs) as the preferred solution for deep water, high pressure and high temperature applications.
This paper introduces an effective engineering SCR fatigue screening methodology for FPSO applications. The focus of this study is to better understand SCR fatigue performance at Touch Down Point (TDP) and develop a simple but reasonable correlation between FPSO porch motion and the riser dynamic stress response at TDP. This methodology enables one to perform the porch motion statistics analysis and the riser dynamic response analysis independently. By using the wave screening approach, SCR fatigue feasible map can be effectively developed. The paper presents an example performing the fatigue screening evaluation. SCR feasibility design flow chart for FPSO application is also addressed.
Particular for FPSO application in a new development, the fatigue feasibility prediction approach along with the strength feasibility check can help the project make the informative decision on the overall FPSO and riser system selection at the early stage of the development.
Dynamic Behavior Analysis of a Deepwater Self Standing Hybrid Riser System
Authors: Morooka Celso K. , Shiguemoto Denis A. 
Published: August 2013

Self Standing Hybrid Riser (SSHR) system is an attractive option for deepwater application. The system is composed by a vertical riser pipe coming from the sea bottom to a subsurface buoy which is placed in around one hundred meter water depth from the sea surface. It is connected to a floating production facility at the sea surface by a flexible jumper. It almost eliminates all the undesired dynamic effects from ocean waves, in addition to relief the total riser system weight from the floating platform. Recent discoveries of petroleum in ultra-deep water Pre-salt Offshore Brazil stimulated development of innovative and nontraditional riser system configurations.
The present work deals with the dynamic behavior of a SSHR system excited by sea current, waves and displacements induced by sea surface platform motions. In plane and out of plane displacements for the SSHR system is analyzed and subsurface buoy maximum motions amplitude have been observed. Effects from current drag and vortex induced forces are investigated by numerical simulations of the dynamic behavior of the SSHR system.
Analysis procedure is presented with details, and fundamentals of the semi-empirical approach for hydrodynamic drag and vortex induced forces in the riser length and subsurface buoy are described. Numerical simulation results are presented, and evaluations are conducted for deepwater condition. Maximum amplitude of vibration is observed near from to lock-in conditions, and effects of the subsurface buoy vortex induced motion (VIM) are discussed. Hydrodynamic forces previously obtained from reduced model tests are used for the numerical approach.
Methodology for Thermoplastic Umbilical Cross Section Analysis
Authors: Silva Danianderson , Balena Rosianita , Lisbôa Rafael 
Published: August 2013

Umbilicals are composite cables responsible for communication, control and power supply of offshore systems for oil exploitation. They can be composed of elements such as power and signal cables, hoses, tubes and fiber optics. Due to their critical role of providing control and power, umbilicals properties and operational limits must be correctly calculated in order to prevent failures, which can be costly and harmful to the environment.
In order to address these needs, the main goal of this paper is to study the viability of using a finite element analysis tool for calculating the allowable bending radius (ABR) and the crush resistance of these cables. Using this tool, the engineer can have a sound basis for choosing the best cross section design at early stages of the project.
The ABR is particularly important at the point where the umbilical touches the seabed, named touchdown point (TDP). This parameter limits the possible operational configurations for the cable and has a significant influence in its fatigue lifespan. Currently, the methods used to predict the ABR of thermoplastic umbilicals are mostly empirical and/or based on samples, but, as we go to deeper areas — as the recent ultra-deep water field discoveries in Brazil, Angola and others — more accurate ways of estimating this parameter are needed.
Another effect of the higher water depths is the increase of tension on umbilicals during installation. Therefore, tensioners with higher load capacity are needed, requiring umbilicals with higher crush resistance. Sample testing during a qualification program is the main method to obtain the value of this parameter, but is costly.
Due to its reliability and relative low costs compared to sample testing, the use of a finite element tool is an attractive alternative for obtaining these limits. In this paper, crush resistance and ABR will be calculated for thermoplastic umbilicals — the most common type of umbilical used in Brazilian offshore oil exploitation — and the results will be compared with the ones achieved by traditional methods. This comparison shows the applicability of using finite element analysis for determining these parameters.
Design and Modelling of Accidental Ship Collisions With Ice Masses at Laboratory-Scale
Authors: Kim Ekaterina , Storheim Martin , von Bock und Polach Rüdiger , Amdahl Jørgen 
Published: August 2013

Knowledge about the level of damage after a collision with an ice mass is necessary for designing ships and offshore structures operating in ice-infested waters. An understanding of the physical processes during such a collision is needed to prevent (or limit) accidents, causing loss of life, the loss of a ship or environmental pollution. This study was motivated by the lack of experimental data on ship collisions with ice masses where both the ship and the structure undergo deformations. Laboratory experiments of accidental collisions with ice masses (ACIM) are essential to verify current methods for integrated analysis of the crushing and deformation of the ice and the steel structure. ACIM tests are sensitive to the structural design, i.e., the design of a structure that is flexible enough in relation to the ice mass. Both the ice and the structure should be able to deform during the collision event. The paper addresses issues related to the planning of ACIM at laboratory scale with special emphasis on the choice of:
(i) process of ice manufacturing and ice mechanical properties;
(ii) flexibility of impacted structure;
(iii) scaling of the experiment.
Experimental setup of laboratory-scale ACIM for the Aalto Ice Tank is proposed. Non-linear finite element analysis is used as a tool to predict structural damage and to guide the planning of collision experiments. The predicted damage of the test specimens caused by collision is presented.