bluuebunny/crossref_metadata_2025_split huggingface dataset:
Walking of Long Pipelines With Multiple Buckles: Can a Trend Be Trusted?
Authors: Carneiro Daniel , Rathbone Andrew 
Published: September 2018

Walking of long pipelines with multiple buckles is usually self-limiting. The buckles break the ‘long’ pipeline into multiple ‘short’ ones that are prone to walk. However, as temperature decays over the length of the pipeline, the ‘short’ sections further downstream might become cyclically constrained and eventually anchor the full pipeline length. Walking of the hot end would then slow down and cease.
This tapering down can take a large number of cycles, and not seem obvious when after a fair number of cycles, a small value of accumulated axial displacement per cycle is still observed in FEA. Often, designers would stop the analyses at some stage and assume the small rate will continue indefinitely. This can be overconservative, as a limit will often exist — which is demonstrated using first principles in the paper.
On the other hand, extrapolating without full understanding of the underlying processes can be dangerous. For some particular conditions, the trend can suddenly change after continuing unaltered for many cycles. This paper illustrates such change in behavior with the example of a fictitious pipeline seeing a gentle, gradual increase in operational temperature over time. The exercise shows that, after the trend has apparently settled, at a given point the rate of walking can increase again. The conditions that trigger it are shown to be predictable.
Microbiologically Influenced Corrosion on Seabed Chain in the North Sea
Authors: Gabrielsen Øystein , Liengen Turid , Molid Solfrid 
Published: September 2018

The last years Statoil has replaced some of our seabed mooring chain segments. Some of these chains have corrosion pits caused by Microbiologically Influenced Corrosion (MIC).
In 2016 and 2017 one full length of a seabed chain segment, including anchor, was retrieved from a SEMI at approximately 300m water depth in the North Sea. The chain has been 20 years on the seabed. The corrosion on the chain was carefully documented, and showed significant levels of MIC. The extent of the MIC showed a strong dependency on seabed contact and how well the chain was buried in the sediments. The observed MIC is caused by Sulphate Reducing Bacteria (SRB). After corrosion identification, the chain has also been subject to full scale fatigue testing.
This paper presents the technical condition of the seabed mooring chain, describing the different levels of MIC, typical SRB corrosion attacks, and the results from the fatigue testing.
Effect of Moonpool Shape and Dimensions on Drillship Operability
Authors: Chalkias Dimitris , Krijger Jan Willem 
Published: September 2018

All modern drillships are equipped with moonpools, through which drilling and other subsea operations are performed. The operability of the vessel, is the percentage of time that the vessel can perform a specific operation in a specific location not limited by environmental conditions. Specific operations such as lowering a BOP or X-tree through the splash zone, have strict operability criteria and often a drillship is waiting on weather to perform these operations.
In this paper, the underwater shape of the moonpool of a drillship is varied and the operability of the vessel is calculated and compared to the original shape. Ten moonpool configurations are used for the study. The GustoMSC “Galene” moonpool shape is used which is comprised of an upper and a lower chamber. The lower chamber or cutout step dimensions such as length, breadth and height are the variables for this study.
An analytical method originally proposed by Newman [1] and extended by Chalkias and Krijger [2] is used in this optimization study. The method is comprised of a potential flow radiation/diffraction solver, where the moonpool modes are accounted as additional separate generalized modes. In this way each mode can be damped separately.
In order to calculate the damping factors for the moonpool modes used in the potential flow solver, free decay CFD calculations are performed and a P-Q analysis is applied on the resulting time-traces. Additional regular wave CFD calculations are performed for method validation purposes. The efficiency and ease of the proposed method is demonstrated by calculating the responses and operability of multiple shape variations in the frequency domain.
Turbulence and Wake Effects in Tidal Stream Turbine Arrays
Authors: Nuernberg Martin , Tao Longbin 
Published: September 2018

Electricity generation from tidal current can provide a reliable and predictable addition to a reduced carbon energy sector in the future. Following the deployment of the first multi-turbine array, significant cost reduction can be achieved by moving beyond demonstrator projects to large scale tidal turbine arrays. The interactions between multiple turbines installed in close proximity can affect the total electricity generation and thus require knowledge of the resulting flow field within and downstream of the array.
Results are presented for experimental and numerical studies investigating the flow field characteristics in terms of velocity deficit and turbulence intensity in a staggered tidal turbine array section. Multiple configuration with varying longitudinal and transverse spacing between devices in a three-turbine array are tested.
Comparison between numerical and experimental flow characteristics shows that open source numerical models with dynamic mesh features achieve good agreement and can be used for the investigation of array wake effects. The standard k–ω SST shows good agreement with experiments at reduced computational efficiency compared to higher order turbulence models (RSM). The importance of mixing with ambient flow is highlighted by identifying areas of significantly reduced velocity recovery within closely spaced arrays where ambient flow does not penetrate between adjacent wakes.
Drilling Data Quality Management: Case Study With a Laboratory Scale Drilling Rig
Authors: Geekiyanage Suranga C. H. , Sui Dan , Aadnoy Bernt S. 
Published: September 2018

Drilling industry operations heavily depend on digital information. Data analysis is a process of acquiring, transforming, interpreting, modelling, displaying and storing data with an aim of extracting useful information, so that the decision-making, actions executing, events detecting and incident managing of a system can be handled in an efficient and certain manner. This paper aims to provide an approach to understand, cleanse, improve and interpret the post-well or realtime data to preserve or enhance data features, like accuracy, consistency, reliability and validity.
Data quality management is a process with three major phases. Phase I is an evaluation of pre-data quality to identify data issues such as missing or incomplete data, non-standard or invalid data and redundant data etc. Phase II is an implementation of different data quality managing practices such as filtering, data assimilation, and data reconciliation to improve data accuracy and discover useful information. The third and final phase is a post-data quality evaluation, which is conducted to assure data quality and enhance the system performance. In this study, a laboratory-scale drilling rig with a control system capable of drilling is utilized for data acquisition and quality improvement. Safe and efficient performance of such control system heavily relies on quality of the data obtained while drilling and its sufficient availability. Pump pressure, top-drive rotational speed, weight on bit, drill string torque and bit depth are available measurements.
The data analysis is challenged by issues such as corruption of data due to noises, time delays, missing or incomplete data and external disturbances. In order to solve such issues, different data quality improvement practices are applied for the testing. These techniques help the intelligent system to achieve better decision-making and quicker fault detection. The study from the laboratory-scale drilling rig clearly demonstrates the need for a proper data quality management process and clear understanding of signal processing methods to carry out an intelligent digitalization in oil and gas industry.
A Transient Flow Model for Investigating Parameters Affecting Kick Behavior in OBM for HPHT Wells and Backpressure MPD Systems
Authors: Gomes Dalila , Nilsen Marius S. , Frøyen Johnny , Bjørkevoll Knut Steinar , Lage Antonio C. V. M. , Fjelde Kjell Kåre , Sui Dan 
Published: September 2018

Gas kicks can occur during conventional drilling operations, in which case the well has to be shut in and the kick circulated safely out of the system. In back pressure managed pressure drilling (MPD) systems, one can tolerate minor influx sizes before the well is shut in.
However, when using oil based mud, solubility issues can complicate the picture making both kick detection and safe handling of kicks more complex. For sufficient large pressures the solubility can be infinite. A kick can also be taken undetected and reach the riser before the free gas suddenly emerge with a corresponding volume expansion that can unload the riser. Managed pressure drilling can be based on having a rotary control device on top of the riser, which makes it possible to add a backpressure on top to dampen the volume expansion, but possibly also change the depth where free gas emerges. It has been shown in another paper how one can use transient models to predict what kind of surface pressure is needed to maintain a constant bottomhole pressure when free gas emerge.
In this paper, a fully transient model developed for a research cooperation between a research institute and Academia will be presented. The model includes behavior of kicks in oil based mud and solubility issues. The model will be used to study the behavior of kicks in riser when considering a backpressure MPD system with special focus on MPD from floaters. One objective will be to show how the results can be impacted by accuracy in the calculation method due to the amount of numerical diffusion present. Another objective will be to show how the PVT model adopted can affect the results. In addition, one will study the impact on results when varying physical input parameters like kick size, magnitude of pore pressure and the geometry of the riser.
TELWIND: Numerical Analysis of a Floating Wind Turbine Supported by a Two Bodies Platform
Authors: Armesto José A. , Jurado Alfonso , Guanche Raúl , Couñago Bernardino , Urbano Joaquin , Serna José 
Published: September 2018

This paper presents a numerical study of an innovative floating wind turbine developed by ESTEYCO S.A.P. as part of an intensive R&D roadmap initiated ten years ago. The concept is called TELWIND, an evolved spar concept composed by a telescopic tower and two independent concrete bodies: the upper tank (acting as buoyancy body) and lower tank (acting as ballasting body), connected by suspension tendons. An ad-hoc numerical model has been developed by IHCantabria, calibrated and validated, based on a set of large scale laboratory tests performed at the Cantabria Coastal and Ocean Basin (CCOB), located at IHCantabria, Santander, Spain.
The inhouse numerical model is a fully coupled model which comprehends three main modules: i) Hydrodynamic model that analyses the coupled hydrodynamics of floater and ballast. ii) Mooring and tendon module, and iii) Aerodynamic model. The full description of the numerical model is summarized, as well as the validation procedure followed. Finally, the validation of the numerical model is shown.
High Fidelity Simulation of Multi-MW Rotor Aerodynamics by Using a Multifan
Authors: Battistella Tommaso , Paradinas Daniel De Los Dolores , Urbán Albert Meseguer , Garcia Raul Guanche 
Published: September 2018

During the last decades the offshore wind energy sector has experienced large developments. Despite bottom fixed wind turbines have been widely used, some their limitations have brought to scout and develop concepts based on floating support structures.
The behavior of such structures is affected by forces of different nature, so the analysis of these structural systems becomes complex and requires an accurate definition of their dynamics. This is one of the reasons for which the numerical simulations can be highly improved from experimental tests at reduced scale.
The interaction between hydrodynamic forces and the structure is investigated experimentally by means of wave tank tests. In these circumstances the correct representation of the aerodynamic forces is not trivial due to laboratory scale law conflicts. These issues can be eased by using hybrid systems.
This work aims to describe a hybrid system developed by IH Cantabria. The system is meant to define the most significant aerodynamic loads affecting the dynamic performance of a floating wind turbine by using an aerodynamic model (BEM), while their generation in the scaled model is obtained by using a multi-fan system.
This approach successfully satisfies issues related to the scalability of the aerodynamic forces and their variability due to the turbine controller and wind variability. Nevertheless, some shrewdness have to be taken in order to comply with the following matters.
The correct representation of the dynamic effects relative to the aerodynamic forces requires high frequency calculations. For this reason some simplifications on the aerodynamic model must be taken. This work explains the criteria used to define the simplifications to be adopted, showing the low impact they have on the tests results. On the present paper it will be demonstrated the capabilities of the multi-fan that was chosen to reproduce the rotor aerodynamics. Moreover, it will evidence the high fidelity of the forces developed by the multi-fan, both in terms of amplitude and reactiveness on the forces fluctuations.
The final section will prove the ability of the hybrid system to reproduce with high fidelity and large flexibility the aerodynamic load conditions desired in lab scale wave tank tests.
The Effect of Blade Pitch and Reynolds Number on the Performance of Cross-Flow Turbines
Authors: Somoano Miguel , Huera-Huarte Francisco J. 
Published: September 2018

In this work we studied experimentally the performance of a three straight-bladed Cross-Flow Turbine (CFT) based on symmetric NACA-0015 profiles, with a chord to rotor diameter ratio c/D = 0.16. The fixed pitch angle of the blades of the CFT can be changed, so experiments were carried out with a β = 0° and with a β = 8° toe-out blade pitch. Tests were made in a wind tunnel facility at three different turbine diameter Reynolds numbers in the range ReD = 3 · 105 – 5 · 105. The Tip Speed Ratios (TSRs) covered in the experiments went up to 2.6.
Results showed how as the Reynolds number based on the diameter of the turbine, had practically no effects on the performance of the CFT for the experiments conducted with β = 0°, in the case of β = 8° toe-out, the range of ReD covered a transitional region in which the torque produced by the blades overtook the aerodynamic resistive torque imposed by the arms (blade supports) of the CFT yielding high performances for the case with ReD = 5 · 105.
Cooperation of the Ports at the Time of the Large-Scale Disaster Such As High Tide and Tsunamis
Authors: Takahashi Koji 
Published: September 2018

The Great East Japan Earthquake in Japan paralyzed functions of Japanese ports operated by the local governments in 2011. If an anticipated Nankai Trough Earthquake occurs, port functions may be paralyzed just as in 2011 under the current port operation system conducted by the local governments. Today, horizontal/vertical division of work has been expanded in the global economy, and thus, paralysis of Japanese port functions may result in severe damage on the global economy. Using the sacrifice model, the variation in container logistics caused by earthquakes was analyzed for the Nankai Trough Earthquake.
Through the case of Japan, it was demonstrated that the powerful leadership of the national government could establish port operations resistant to large-scale natural disasters.
This paper has developed the author’s research [1]–[13].
Research on Influence of Horizontal Offsets of Underwater Equipment Based on Pendulous Installation Method
Authors: Wang Jingqian , Sun Liping , Deng Zhongchao , Ma Gang , Zhu Xiaomeng , Hou Zhicheng 
Published: September 2018

Large underwater equipment used in deep-sea engineering, which needs mooring line in order to hang down while using pendulous installation method in 1500m deep-water installation. During the procession, the mooring line will suffer the vessel’s pull, large equipment’s traction, fluid force leading to elongation, bending and other deformation, so need to analyze its motion. Aiming at the numerical simulation problem of underwater equipment installed by pendulous installation method in deep-water environment, this paper combines lumped mass method, three-dimensional potential theory and Morison equation to establish the analysis model of the whole installation system. Under the different horizontal dropping offsets of the equipment, this paper computes not only tension of mooring line, but motion performance of underwater equipment and working vessel during the pendulous lowering phase.
The Pendulous Installation Method (PIM) puts a working vessel, a mooring line and a underwater equipment installed in succession, and there is a coupling interaction among them, so it is essential to do time-domain coupling analysis. So the Orcaflex Software is used to simulate the entire deep-water installation system. Using different horizontal dropping position as a variable, we can get the contrast about the different movement states of the mooring line and underwater equipment, and finally we will get the conclusion.
Research Regarding the Conceptual Change Observed in the Sea City Concept
Authors: Sugahara Ryo , Kuroyanagi Akio 
Published: September 2018

From the 1960th to 1980th years in the second half of the 20th century, numerous “sea city concepts” were proposed as a new city image. Among these concepts, in Japan, the sea city concept reflecting the current urban development situation of that time, was drawn by the architects as an image of the ideal city.
During that period, in Japan for the purpose of the further economic development, the landfilled industrial zones were created in the surroundings of large metropolitan areas of Tokyo, Osaka and Nagoya. It led to the concentration of the population due to the people fleeing to the big cities from the provinces for employment, which created various problems of big cities such as population overcrowding, land shortage, traffic jams, air pollution, etc., so the different tasks became apparent.
As a way to solve such problems, a sea city plan has been proposed. The oldest initiative was the Tokyo Bay concept of 1958 which proposed the creation of a new city by creating a new land by landfilling Tokyo Bay. However, that initiative only covered the expansion of the existing land, and didn’t make any advantage of “ocean” resources.
For that reason, the further proposals subsequently enabled taking advantage of the sea by creating the canals, artificial islands or pile-style structures which led to adoption of proposal to float up. After that, the sea city concepts basing on the floating type had increased, and the subjected water area transited from the shallow water to the offshore area.
Furthermore, the authors are planning to arrange the process of transition of the concept of the sea city by taking into account the changes the way oceans are treated and the structures relative to time.
Cargo-Flow-Oriented Design of Supply Vessel Operating in Ice Conditions
Authors: Kondratenko Aleksander A. , Tarovik Oleg V. 
Published: September 2018

Due to the dynamic development of the oil and gas fields in the Arctic, the challenges of supply fleet sizing and composition in this region are becoming relevant. In most studies, the Arctic is mainly associated with ice conditions, but it is not the only factor that influences the design of platform supply vessels (PSV) and corresponding marine transport systems (MTS) for this region. The structure of cargo flow (i.e. its distribution by cargo types) affects the supply system significantly. It defines the level of utilization of vessel capacity that determines transport efficiency. At the same time, the literature represents this aspect poorly.
This paper describes an approach to optimize supply fleet configuration by the criterion of total cost considering both non-stationary ice conditions and structure of cargo flows. The cargo-flow-oriented design concept incorporates the detailed calculation model of PSV and the special tactical planning algorithm. PSV model allows considering the influence of cargo spaces on the main characteristics and operational parameters of the ship. It covers the main design aspects of PSVs: general arrangement; lines plan; resistance in open water and ice; engine and propeller characteristics; hydrostatics; capacity and mass calculation. The pseudo-optimal tactical planning algorithm is intended to build the plan of voyages and to set the size of fleet considering the structure of cargo flow.
As the test example, we examine a task of servicing the group of platforms in the Kara Sea. The case study shows that cargo flow structure has a high influence on the efficiency of PSVs in case of high-load operation; while a widespread “deck-cargo” approach is unable to consider this aspect because it ignores the vessel’s carrying capacity and payload. The conclusion about a higher efficiency of PSV compared to AHTS with the same displacement was drawn.
Wave Load Acting on Advanced Spar in Regular Waves
Authors: Hirai Takayuki , Sou Akira , Nihei Yasunori 
Published: September 2018

Offshore wind turbines have been investigated and developed as one of the renewable energies. In Japan, the research and development of floating type offshore wind turbines have been carried out because the water around the country is too deep to settle the bottom mounted type.
In this paper, we investigate the effects of the diameter of the column floater of the advanced spar in regular wave by using open source computational fluid dynamics software OpenFOAM. We use olaFOAM which equipped with the functions to set the boundary conditions of wave generation at the inlet and wave absorption at the outlet. The forces acting on a spar obtained by the numerical simulation and Morison’s equation are compared to examine the validity of the numerical model. A good agreement between them confirms the validity of the numerical method. Then we simulate numerically the effects of the column diameter on the flow around the advanced spars and the wave load. The result clarifies that Morison’s equation overestimates the wave force, and the difference increases with the column diameter. For more detailed analysis we divide the advanced spar into three parts, the upper spar above the column, the column floater and the lower spar below the column. As a result, we find that the difference between the wave load acting on the column by Morison’s equation and that by numerical simulation is dominant due to the flow separation around the column. Finally we modify the load coefficients of Morison’s equation for the column so that the modified equation can accurately evaluate the wave load acting on the advanced spar.