bluuebunny/crossref_metadata_2025_split huggingface dataset:
Drilling Riser Analysis During Installation of a Wellhead Equipment
Authors: Sevillano Lucas C. , Morooka Celso K. , Mendes Jose Ricardo P. , Miura Kazuo 
Published: November 2013

In offshore petroleum drilling, the BOP stack is run into the sea by a string, composed of long and wide-bore pipes, called the marine drilling riser. It also connects the BOP stack (BOP + LMRP) on the wellhead to the drilling vessel at the sea surface, serving as conduit between them.
While being lowered down, a special riser spider is used to support the riser. During this operation, the hanging riser is under the effects of sea current, waves and displacements induced by sea surface drilling vessel motions.
The discovery of petroleum fields in deeper waters, usually in remote and harsh environments, makes it a requirement for the riser to withstand more severe conditions. Nevertheless, riser design and failure analysis during this operation is a seldom studied topic, even though drilling in ever increasing water depths imply the riser is subject to risks inherent to running a BOP for a longer period of time. It is of utmost importance the adequate modeling of the system’s response during this operation, in order to safely evaluate failure cases due to extreme static and dynamic stresses.
As such, the present paper describes and proposes a methodology developed for the analysis of extreme stresses that act over the riser during the BOP running. Case studies were conducted for a water depth up to 2000 m. Numerical simulations were run to evaluate system’s static and dynamic behavior due to environmental loading.
As a result conclusions were drawn regarding operation limits in ultra-deep waters. Results are shown through charts that delimit ocean conditions and vessel’s response that are secure to operate under.
Engineering Critical Assessment in Sour Service by Fracture and Fatigue Small Scale Sour Testing
Authors: Nakamura Jun , Hisamune Nobuyuki , Fukuba Tetsuya , Scott Colin Stuart , Thodla Ramgopal , Gui Feng 
Published: November 2013

Engineering critical assessments (ECA) have increasingly become a routine part of pipeline design to determine tolerable flaw sizes for weld defects. These assessments are now being applied to pipeline systems in deeper water with increased loadings arising from responses to thermal and pressure cycling. Often these are flowline systems in which fatigue damage is exacerbated by the presence of aggressive internal conditions.
Deep water flowlines operating at high temperatures and pressures need to be designed to accommodate issues such as significant end expansion, walking and lateral buckling. Offshore flowlines are subject to large thermal transients particularly during shut down. These thermal transients tend to vary from about 200°F to ambient temperature and place a large fatigue demand on the pipelines. The transients typically are very low frequency events with high amplitudes, which can lead to lateral buckling. The loading rates associated with the transients are very slow, hence the toughness properties of the material in environments at low loading rates is important. The pipelines are also subject to high stress and thus need to have good toughness properties. Riser materials are also subject to significant fatigue loading, though under conditions different from flow lines. They are typically pre-loaded and operate under smaller amplitudes of loading and at higher frequencies associated with wave motion.
Currently for a number of offshore sour service pipelines, Engineering Critical Assessment (ECA) for flaw acceptance criteria are performed using knockdown factors up to 50X on fatigue crack growth rates. The toughness values used for the analysis are performed assuming a CTOD of 0.1 mm. In order to develop material chemistry and heat treatment procedures for offshore pipelines, it is important to be able to understand the fracture toughness behavior as well in sour environments.
In order to evaluate the safety of offshore flowlines and risers applications fatigue and fracture toughness properties of X80 parent pipe material in sour environments were determined. The data developed was used to develop an ECA framework for flowlines and riser applications.
Model Testing of Turret-Based Drill Ship in Ice Conditions
Authors: Kovalyov Maksym V. , Dobrodeev Aleksey A. , Blagovidova Iryna L. , Sazonov Kirill Ev. , Kolchenko Leonid V. , Klementieva Nataliya Yu. , Blagovidov Lev B. 
Published: November 2013

Recently, process platforms and drill ships featuring anchor sea-keeping system equipped with a turret arrangement have increasingly been proposed for deep-water offshore applications to be operated in freezing seas. A possibility of environmentally-oriented yawing with the ship’s bow ahead of the resulting vector of environment actions provides the major advantage of the turret system use. The turret system allows passive positioning of the ship without activation of any propulsion means or thrusters, which is particularly important in ice conditions where ship controls can be difficult to operate.
CDB Corall PJSC designed a promising turret-based drill ship (TBDS) intended to perform drill operations in seas of Russian Arctic region. The design is substantially different from drill ships and platforms conventionally considered for similar purposes. The adopted design solutions ensure significantly higher drill ship performances in ice conditions.
The report includes results of TBDS model tests performed in the model basin of the Federal State Unitary Enterprise “Krylov State Research Centre”. Tests of ice resistance and tension of the anchor sea-keeping system have been incorporated in the test program, while the model was being interacted with the variable-thickness ice sheet at a 0° heading. Testing to investigate behavior of the interacted with ice ridge formations have also been performed at the same heading.
The study of passive model yawing at 90° and 170° conditions made up a highly important part of the program. Such tests were performed both for model/ice sheet and model/ice ridge interaction types. In addition to measuring force parameters during the tests, changes in heading, heel and trim, as well as model displacements were also determined. Testing proved high ice resistance and maneuverability of the test model.
The report includes comparison of the results obtained in model basin tests with other experimental data for models fitted with turret arrangement and anchor sea-keeping system features. The comparison suggests considerable advantages of the new solution versus previously considered options.
Estimation of Constraint Factor on the Relationship Between J Integral and CTOD for Offshore Structural Steel Weldments
Authors: Moon Dong Hyun , Lee Jeong Soo , Lee Jae Myung , Kim Myung Hyun 
Published: November 2013

As ships and offshore structures become larger than before the usage of high strength steel and ultra thick plate has been increased. However, the thick plates have disadvantages with respect to brittle fracture and fatigue strength. Elastic plastic fracture mechanics (EPFM) is the domain of fracture analysis which considers extensive plastic deformation at crack tip prior to fracture. The J integral and crack tip opening displacement (CTOD) have been commonly used as parameters for EPFM analysis. The relationship between these parameters has been studied by industry and academia. The plastic constraint factor can serve as a parameter to characterize constraint effects in fracture. Therefore, the characteristics of plastic constraint factor are important in EPFM analysis.
In this study, the relationship between J Integral and CTOD was investigated by conducting 3-point bending tests using single edge notched bend (SENB) specimens. Two types of specimens were fabricated. One is API 2W Gr.50 welded by means of flux cored arc welding (FCAW) with heat input 15kJ/cm, and the other is API 2W Gr.50 welded by means of submerged arc welding (SAW) with heat input 45kJ/cm. The plastic constraint factor was estimated considering heat input, temperatures at weldment and heat affected zone (HAZ).
At-Sea Experiment of a Hybrid SPAR Type Offshore Wind Turbine
Authors: Ishida Shigesuke , Kokubun Kentaroh , Nimura Tadashi , Utsunomiya Tomoaki , Sato Iku , Yoshida Shigeo 
Published: November 2013

Ministry of the Environment of Japan started the national demonstration project of Floating Offshore Wind Turbine (FOWT) in 2010 FY. In this project two SPARs with different scales are used. The first half-sized model, supporting a 100kW wind turbine, was installed in 2012 and is currently in operation. It is characteristic that the floater has a hybrid structure, i.e., the upper part is constructed of steel and the lower part of pre-stressed concrete and that the turbine is downwind type of horizontal axis.
The FOWT is equipped with many sensors for measuring motions of 6 DOF, the strain of the steel / concrete parts and other factors. In this paper the measuring system is presented. In September 2012, the FOWT was attacked by a huge typhoon and it survived, although the measured wave height exceeded the designed value. The measured record of the floater in the storm is also presented.
Steep Wave Loads From Irregular Waves on an Offshore Wind Turbine Foundation: Computation and Experiment
Authors: Paulsen Bo Terp , Bredmose Henrik , Bingham Harry B. , Schløer Signe 
Published: November 2013

Two-dimensional irregular waves on a sloping bed and their impact on a bottom mounted circular cylinder is modeled by three different numerical methods and the results are validated against laboratory experiments. We here consider the performance of a linear-, a fully nonlinear potential flow solver and a fully nonlinear Navier-Stokes/VOF solver. The validation is carried out in terms of both the free surface elevation and the inline force. Special attention is paid to the ultimate load in case of a single wave event and the general ability of the numerical models to capture the higher harmonic forcing. The test case is representative for monopile foundations at intermediate water depths.
The potential flow computations are carried out in a two-dimensional vertical plane and the inline force on the cylinder is evaluated by the Morison equation. The Navier-Stokes/VOF computations are carried out in three-dimensions and the force is obtained by spatial pressure integration over the wettet area of the cylinder. In terms of both the free surface elevation and the inline force, the linear potential flow model is shown to be of limited accuracy and large deviations are generally seen when compared to the experimental measurements. The fully nonlinear Navier-Stokes/VOF computations are accurately predicting both the free surface elevation and the inline force. However, the computational cost is high relative to the potential flow solvers. Despite the fact that the nonlinear potential flow model is carried out in two-dimensions it is shown to perform just as good as the three-dimensional Navier-Stokes/VOF solver. This is observed for both the free surface elevation and the inline force, where both the ultimate load and the higher harmonic forces are accurately predicted. This shows that for moderately steep irregular waves a Morison equation combined with a fully nonlinear two-dimensional potential flow solver can be a good approximation.
Assessment of Hull Monitoring Measurements for a Large Blunt Vessel
Authors: Storhaug Gaute , Hareide Ole Jakob 
Published: November 2013

A large blunt vessel was designed for a longer target life than usual in world-wide trade. Due to experience with whipping and springing, special attention to these effects was also made during the design and approval in order to ensure satisfactory strength of the vessel. The vessel was consequently strengthened beyond the minimum industry standard, and it has now been operated for several years.
The owner/operator who observed wave induced vibrations (whipping/springing) onboard, equipped the vessel with a hull monitoring system from a recognized supplier. After a few years of measurements, the data was sent to DNV for assessment of the effect of the vibrations and the consequence for the particular design.
The data shows that the vessel has been trading in more demanding areas than assumed during design, but the environment is less severe than the North Atlantic. The measured fatigue life based on a stress concentration factor of 2.0 has been estimated to be well below the design life, so special attention to cracks need to be taken from now on if the trade remains the same in the future. No cracks have, however, been identified so far during inspection.
The vessel has also experienced two severe storms. The maximum loading level has been higher than ever assessed by DNV before based on hull monitoring data of blunt vessels. The rule of thumb value of 20% increase on extreme loading for blunt vessels due to whipping has been exceeded. The wave bending moment according to IACS URS11 has also been exceeded without whipping. The ultimate collapse strength has been assessed and compared to the measured dynamic loading and allowable still water loading. When whipping is assumed fully effective to contribute to collapse, the safety margin is still above 1.0, but on the borderline of what is desirable. However, if the vessel had not been strengthened beyond the original design due to the concern of whipping and springing, the safety margin would have been below 1.0. This may be the first documentation of a vessel that has been saved from breaking in two due to addressing springing and whipping properly during design.
Experimental Investigation of the Effect of Waves, Ventilation and Cavitation in Bollard Pull Conditions
Authors: Hagesteijn G. , Brouwer J. 
Published: November 2013

Ventilation is a feared working condition of ship propulsors, especially in Dynamic Positioning operation, since it leads to the lost of thrust of the propeller resulting into an uncontrollable ship. Experience showed that the risk of ventilating propellers was negligently underestimated in traditional towing tank experiments but better predicted in depressurised towing tanks, where the ambient pressure is scaled down according to Froude similarity.
In 2012 MARIN’s Depressurized Wave Basin (DWB) has taken into service. This unique facility is the only one in the world that is able to generate waves in a large depressurized towing tank. This ensures correct representation of the pressure inside the enclosed ventilation bubbles and vortices, resulting into a correct physic behaviour. The EU-funded Streamline project was the first project for which ventilation inception measurements were carried out in the DWB. Tests were carried out with a fully instrumented podded ship model, sailing and in bollard pull condition, in waves and depressurised conditions.
In order to acquire detailed load measurements, MARIN used their in house developed 6 component and 5 component transducers. The 6 component transducer was used for measuring the omnidirectional propeller loads, while the 5 component transducer was used for measuring 2 blade forces and 3 blade moments. At the same time synchronised high speed video recordings were made to acquire insight in the occurring phenomena. In the present paper a description of the test set up will be presented briefly, followed by a discussion of the recordings and the observations that were made for bollard pull condition in waves.
Summary of Conclusions and Recommendations Drawn From the DeepCwind Scaled Floating Offshore Wind System Test Campaign
Authors: Robertson Amy N. , Jonkman Jason M. , Goupee Andrew J. , Coulling Alexander J. , Prowell Ian , Browning James , Masciola Marco D. , Molta Paul 
Published: November 2013

The DeepCwind consortium is a group of universities, national labs, and companies funded under a research initiative by the U.S. Department of Energy (DOE) to support the research and development of floating offshore wind power. The two main objectives of the project are to better understand the complex dynamic behavior of floating offshore wind systems and to create experimental data for use in validating the tools used in modeling these systems. In support of these objectives, the DeepCwind consortium conducted a model test campaign in 2011 of three generic floating wind systems: a tension-leg platform (TLP), a spar-buoy (spar), and a semi-submersible (semi). Each of the three platforms was designed to support a 1/50th-scale model of a 5-MW wind turbine and was tested under a variety of wind/wave conditions.
The focus of this paper is to summarize the work done by consortium members in analyzing the data obtained from the test campaign and its use for validating the offshore wind modeling tool, FAST.
Design and Estimated Economic Performance of a Floating Axis Marine Current Turbine in Kuroshio Ocean Current
Authors: Akimoto Hiromichi , Tanaka Kenji , Hara Yutaka , Uzawa Kiyoshi 
Published: November 2013

Although ocean currents are more stable than wind, the present cost of energy produced by ocean current turbine is considered to be higher than that of offshore wind turbines. It is caused by the expensive cost of submerged devices and difficulties of their maintenance. To solve the problem, the authors are developing a new concept of a cross flow turbine for high economic performance. The turbine axis of the concept is not fixed in the upright position for the reduction of supporting structures and device cost.
Since a firm foundation is not available in ocean environment, discarding the idea of fixed turbine axis position is a very natural approach in ocean engineering. The economic performance of the proposed turbine is estimated based on the existing cost analysis of floating wind turbines and ocean plants. Although there are remaining problems of high mooring tension, possible changes of ocean current path and survivability in rough sea conditions, the result shows favorable economic performance of the concept.
Employing Visual Image Correlation for the Measurement of Compressive Strains for Arctic Onshore Pipelines
Authors: Ozkan Istemi F. , Bandstra Daryl J. , Timms Chris M. J. , Zielinski Arthur T. 
Published: November 2013

The Arctic onshore environment contains regions of discontinuous permafrost, where pipes may be subject to displacement-controlled bending in addition to high hoop stresses due to the pressurized fluids being transported. Considering the displacement-controlled nature of the deformations, strain-based design methodologies have been developed for permafrost pipelines when they are subject to bending and tension, which limit the longitudinal compressive and tensile strains. The widely accepted methodology in the industry to obtain the compressive strain capacity of line pipes subject to bending is to conduct Finite Element Analysis, incorporating material and geometrical nonlinearity calibrated against benchmark full-scale tests (bend tests) [1,2]. During these tests, compressive strains can be measured by various methods. The seemingly obvious choice is to apply strain gauges along the compression face of the specimen with respect to bending (intrados). This method will provide reasonable results until the compressive strain pattern begins to vary due to the initiation of buckle formation, which typically occurs shortly after yield. In order to measure average compressive strain beyond yield and up to buckling, the method used by C-FER Technologies (C-FER) involves using rotation measurement devices (inclinometers) to calculate the strain change between the most compressive and tensile fibres of the specimen (intrados and extrados, respectively) with respect to the bending direction. This value is then subtracted from the tensile strain gauge readings as measured by the strain gauge(s) located on the extrados of the specimen. The average compressive strain values derived from the inclinometer and extrados strain gauge measurements are based on the assumption that the plane sections remain plane.
Recently, five large diameter pipes were bend-tested at C-FER’s testing facility in Edmonton, Alberta. In addition to the compressive strain measurement method used by C-FER described above (C-FER method), a visual image correlation (VIC) camera system was used to survey the strain distribution on the compressive face of the specimens. This paper gives a brief description of the test setup and instrumentation of this test program. The VIC camera setup and measurement technique are described and the overall strain distribution on the bending intrados as measured by the VIC cameras is presented. Strain measured by the VIC system is compared with gauge measurements at local points as well as the average compressive strain behaviour of the specimens obtained through the C-FER method described above. The results show that the VIC system can be a candidate to replace the conventional measurement techniques employed for compressive strain limit testing in support of strain-based design of arctic pipelines.
Efficient Computation and Modeling of Viscous Flow Effects in ComFLOW
Authors: van der Heiden Henri J. L. , van der Plas Peter , Veldman Arthur E. P. , Verstappen Roel W. C. P. , Luppes Roel 
Published: November 2013

In offshore applications, details of viscous flow effects can become relevant when predicting e.g. drag forces on the columns of oil drilling rigs, or the flow around a semisubmersible in figure 1. This motivates a novel approach for efficiently simulating viscous flow effects at high Reynolds numbers with the CFD simulation tool ComFLOW.
In ComFLOW, the Navier–Stokes equations can be solved for one-phase and for two-phase flow. The equations are discretized second-order in space, and second-order in time. An Improved Volume-of-Fluid (IVOF) algorithm is used for free-surface advection and reconstruction [1, 2].
Modeling viscous flow effects in high Reynolds number flows requires a turbulence model that provides accurate results on coarse grids. We pursue to achieve a high local grid resolution in a computationally efficient manner. Both approaches are tested for flows around a square cylinder: grid refinement at Reynolds numbers 10 and 100, and the turbulence model at Reynolds number 22,000.