bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Generic Allocation Algorithm for Optimal 6dof Motion Control Including Interaction Effects and Physical Limitations
Authors: van Daalen Ed 
Published: December 2020

Abstract
In this paper we consider the allocation problem within the context of optimal motion control for floating or submerged bodies. The purpose of our research is to develop an allocation algorithm which allows for (1) multiple bodies with up to six modes for each body, (2) arbitrary actuator types — azimuthing thrusters, propeller-rudder systems etc., (3) arbitrary objective functions, (4) interaction effects such as forbidden zones, and (5) physical limitations such as saturation.
Some ideas presented in [1, 2] were generalised to more widely applicable concepts. Each body has an arbitrary number of actuators, each actuator has an arbitrary number of degrees of freedom. Interaction effects are modelled by means of state-dependent effectivity coefficients. Coupled states, such as propeller thrust and torque, are modelled as linearised constraints. The constrained optimization problem is solved with a combination of Sequential Quadratic Programming and Steepest Descent methods.
The Python implementation is coupled with MARIN’s extensible modelling framework (XMF). We demonstrate the generic allocation algorithm for an underwater vehicle with multiple actuator types, physical limitations and coupled states and for a surface vessel with two propeller-rudder systems and a bow tunnel thruster. The results show that the allocation algorithm is able to handle complex configurations with specific physical limitations and coupled modes while adopting a generic approach.
Development of a Protocol to Couple Wave and CFD Solvers Towards Reproducible CFD Modeling Practices for Offshore Applications
Authors: Bouscasse Benjamin , Ducrozet Guillaume , Kim Jang Whan , Lim Hojoon , Choi Young Myung , Bockman Arne , Pakozdi Csaba , Croonenborghs Eloïse , Bihs Hans 
Published: December 2020

Abstract
Generating waves inside the CFD domain is a topic of interest in the offshore and naval industry. For practical reasons it is useful to use a potential wave kinematic solver (PWKS) to generate incident waves and use this solution to initialize and propagate incident waves in the CFD solver. Protocols to transfer the wave data from PWKS to CFD solver have been developed to ensure the reproduction of the wave kinematics from a PWKS in CFD solvers. Based on the survey results from a number of PWKS and CFD solvers available, the paper presents the various ways to express the solution and what is needed to reconstruct the fields needed in the CFD.
Using Data Science and Artificial Intelligence to Enable Technology-Driven Offshore Opportunities
Authors: Nanda Subrat , Bhatia Meenakshi A. 
Published: December 2020

Abstract
Recent developments in data science are enabling new opportunities for marine and offshore operators to adopt a more effective asset management strategy. The crux of this strategy is to combine data analytics with maintenance records and operational experience to reduce unplanned downtime. This case study focuses on the assimilation and utilization of diverse and mostly unstructured data, which up until now was largely untapped in the marine and offshore industries. The information extracted from such sources is used to identify key trends in equipment reliability and to improve the understanding of assets’ conditions. Such insights are particularly useful for marine and offshore operators in making critical decisions relating to machinery: optimal resource allocation; proactive planning for planned maintenance events and maximizing overall asset availability. From a Classification Society’s perspective such as American Bureau of Shipping (ABS), this allows operators and/or owners to derive Class-based benefits like Condition-Based Maintenance (CBM).
Utilising Advanced Digital Technologies to Provide Automated Drilling Riser Fatigue Tracking to Support Condition Based Maintenance
Authors: Bohan Paul , Lang Donogh , Williams Dara 
Published: December 2020

Abstract
The traditional industry approach to drilling riser joint inspection and maintenance has centered on recertification of riser joints at fixed five-yearly intervals. There are significant potential efficiencies to be gained from moving to a condition-based maintenance regime where inspection intervals are determined based on the actual usage of the riser joint. One of the critical factors driving the requirement for inspection is the fatigue damage sustained by the riser joint during use.
This paper describes a unique drilling riser joint fatigue tracking system that uses the latest digital technologies, advanced automation processes and a state-of-the-art finite element model of the drilling riser to provide an accurate and efficient solution to the challenge of long-term riser joint fatigue tracking. The architecture and operation of the system is described in detail and the application of a fracture mechanics-based approach to fatigue calculation versus the traditional S-N curve-based approach is discussed.
Utilization of Ocean Water for CO2 Capture via Amine Scrubbing
Authors: Ratanpara Abhishek P. , Shaw Alexander , Deshpande Sanat , Kim Myeongsub 
Published: December 2020

Abstract
As the consumption of fossil fuel resources has continuously increased to meet global fuel demands for power generation, atmospheric emissions of greenhouse gases, particularly carbon dioxide (CO2), have rapidly increased over the last century. Increased CO2 emissions have caused serious international concerns about global warming, sea-level rise, and ocean acidification. Although post-combustion carbon capture technology that separates CO2 from flue gas in fossil fuel-fired power plants has contributed to significant migration of atmospheric CO2 emissions, this approach generates considerable amounts of toxic wastewater containing a heavy chemical which is difficult to treat, raises concerns about acute corrosion of metal structures in the facility, and waste of significant amounts of freshwater. In this research, we are particularly interested in reducing the use of freshwater for CO2 capture and generating carbonate minerals, byproducts of CO2 with calcium (Ca2+) or magnesium ions (Mg2+) in ocean water which are useful building blocks for marine animals, such as seashells and coral reefs. In our experimental approach, we attempted to use ocean water with different monoethanolamine (MEA) concentrations and compared the CO2 capturing efficiency with that in DI water. We found that there are considerable benefits of the use of ocean water in CO2 dissolution, showing that a replacement of freshwater with ocean water would be a possible option. In the future, we will further enhance the dissolution of CO2 in ocean water by using nanoparticle catalysts without using MEA, which will be an environmentally friendly method for CO2 capture.
Optimization Design of the Cross-Section of the Umbilical Based on the Pseudo Mechanical Mechanism
Authors: Yang Zhixun , Yin Xu , Shi Dongyan , Yan Jun , Wang Lifu , Lu Qingzhen , Yue Qianjin 
Published: December 2020

Abstract
Umbilical is a critical equipment in subsea production system for extracting offshore hydrocarbon resources, providing electrical and hydraulic power, control signal transmission and chemical injection. A diversity of components such as electrical cables, optical cables, steel tubes and filler bodies compose the cross-section of an umbilical. Different components perform different physical properties, so different cross-sections will present different geometrical characteristic, carrying capacities, thermal distribution, the cost and the ease of manufacture. Therefore, the cross-sectional design of the umbilical is a typical multi-objective optimization problem. The methodology of pseudo mechanical mechanism is introduced in this paper. Pseudo forces are assumed based on geometrical characteristics, carrying capacities and thermal productivities of different electrical cables, optical cables, steel tube and filler bodies. Each component is analogized to a sphere with different diameters on a funnel surface. Moreover, potential energy and interaction force between different components are defined to avoid the overlap and congestion. Then, the pseudo mechanical model is established and mathematics description is presented corresponding to the cross-section of an umbilical. Iteration algorithm procedure is given to solve this problem. Finally, a case of an umbilical is studied and the optimal cross-section is obtained, which is compared with the result used in practical engineering. It is shown that the methodology of the pseudo mechanical mechanism is effective to obtain the optimal design of cross-section of an umbilical.
Assessment of a Polyamide Used in Flexible Pipes After Aging in Deoxygenated Water
Authors: Costa Danyelle , Oliveira Geovanio , Cirilo Leilane , Costa Marysilvia 
Published: December 2020

Abstract
A high-performance polyamide grade of easy processability which presents excellent thermal and mechanical properties such as resistance to fatigue and creep is studied in this work. An accelerated aging of Polyamide 12 samples was performed in stainless steel autoclaves at 120°C in deoxygenated water at pH 8.7 in order to shorten the aging time and avoid oxidation. The samples were retrieved at distinct aging times which were enough to reach the asymptotic portion of the curve of corrected inherent viscosity (CIV) versus aging time. CIV measurements track modifications of the molecular weight due to hydrolysis. Afterwards, the samples were analyzed through their cross section in the core and edge layer in order to investigate changes due to diffusion effects. Differential scanning calorimetry (DSC) analysis assesses the degree of crystallinity and melting temperature. Thermogravimetric analysis (TGA) was employed in order to investigate changes in the thermal stability and the stage of degradation of the samples. Unlike conventional volumetric analysis techniques, the instrumented indentation tests (IIT) in micro-scale were performed to measure the mechanical properties such as elastic modulus (EIT) and hardness (HIT) along the thickness aiming to detect properties gradient between surface and core. The CIV measurements showed a decrease of 46.3% in the aged sample during the maximum aging time compared to the reference material.
Development of a GIS-Based System for Three-Dimensional Spatial Modeling of Offshore Site Investigation Information
Authors: Kim Mingi , Chung Choong-Ki 
Published: December 2020

Abstract
Offshore site investigation is time-consuming and relatively expensive compared to onshore site investigation, because it is affected by severe weather conditions and has low accessibility from the land. Due to these economic and spatial-temporal constraints, it is essential to integrate the available site investigation information for the planning and design of offshore infrastructures. In this study, a GIS-based system was developed to manage and utilize the offshore site investigation data using opensource software. The system mainly performs the function of modeling the geo-information in three dimensions based on the offshore site investigation database. Through the input module, borehole data, geophysical survey data and numerical terrain information are standardized and stored in the database. The three-dimensional spatial modeling module performs outlier analysis of borehole data, subsurface geo-layer stratification, and interpolation of geotechnical properties. For the geo-layer stratification, the geostatistical integration method of borehole and geophysical datasets is adopted as well as conventional geostatistical methods. The optimization method of the results from geostatistical conditional simulation can be used for three-dimensional modeling of geotechnical property. The geoinformation predicted by the analysis module is inserted back into the database. Although this system is designed for offshore site investigation information, it can be used to manage inland and onshore site investigation information. Three-dimensional spatial modeling of site investigation information of an expressway construction site in South Korea was carried out using the developed system and its applicability was verified.
Development and Validation of Passive Yaw in the Open-Source WEC-Sim Code
Authors: Forbush Dominic D. , Ruehl Kelley , Ogden David , van Rij Jennifer , Yu Yi-Hsiang , Tom Nathan 
Published: December 2020

Abstract
A passive yaw implementation is developed, validated, and explored for the WEC-Sim, an open-source wave energy converter modeling tool that works within MATLAB/Simulink. The Reference Model 5 (RM5) is selected for this investigation, and a WEC-Sim model of the device is modified to allow yaw motion. A boundary element method (BEM) code was used to calculate the excitation force coefficients for a range of wave headings. An algorithm was implemented in WEC-Sim to determine the equivalent wave heading from a body’s instantaneous yaw angle and interpolate the appropriate excitation coefficients to ensure the correct time-domain excitation force. This approach is able to determine excitation force for a body undergoing large yaw displacement. For the mathematically simple case of regular wave excitation, the dynamic equation was integrated numerically and found to closely approximate the results from this implementation in WEC-Sim. A case study is presented for the same device in irregular waves. In this case, computation time is increased by 32x when this interpolation is performed at every time step. To reduce this expense, a threshold yaw displacement can be set to reduce the number of interpolations performed. A threshold of 0.01° was found to increase computation time by only 22x without significantly affecting time domain results. Similar amplitude spectra for yaw force and displacements are observed for all threshold values less than 1°, for which computation time is only increased by 2.2x.
CFD Investigation on the Hydrodynamic Characteristics of Blended Wing Unmanned Underwater Gliders With Emphasis on the Control Surfaces
Authors: Guggilla Mukesh , Rajagopalan Vijayakumar 
Published: December 2020

Abstract
Underwater Gliders are unique buoyancy propelled oceanographic profiling vehicles. Their speed and endurance in longitudinal motion are affected by the symmetry, sweep dihedral angle and span of the control surfaces. In the low-velocity regime, these parameters can be varied to examine the flow around the glider. They also affect the lift-to-drag ratio (L/D) essential for the manoeuvring path in longitudinal and transverse motions. In this paper, the sweep angle of the main wing of a blended wing autonomous underwater glider configuration is varied as 10°, 15°, 30°, 45° and 60° and the resulting hull forms are numerically simulated in the commercial software, STARCCM+. The main wing is a tapered NACA0018 section (taken as per the general arrangement requirement) with 1.5m chord at the root and 0. 1m at the tip. The numerical model is validated using the CFD results of NACA0012 airfoil from Sun.C et al, 2015 [1]. The hydrodynamic forces are obtained by varying the angle of attack (α) of the body from −15° to 15°, for flow velocity of 0.4m/s. The hydrodynamic coefficients (lift-to-drag ratios) and flow physics around the wing are analyzed to arrive at an optimum Lift-to-drag ratio for increased endurance.
In Service Experiences With Ship-Shaped Floating Production Units
Authors: Halsne Marita , Oma Narve , Ersdal Gerhard , Kvitrud Arne , Leonhardsen Roger L. , Langøy Morten , Andersen Terje , Bjørheim Lars G. 
Published: December 2020

Abstract
FPSOs and FSOs have been used on the Norwegian continental shelf for petroleum production, storage and offloading since the 1980’s and have been increasingly common since the end of the 1990’s. During these years a significant amount of experience has been gathered.
On the Norwegian Continental Shelf (NCS) shipowners and operators are obliged to report damages and incidents to the Petroleum Safety Authority Norway (PSA).
This article gives an overview of reported incidents related to the structural and maritime systems on offshore ship shaped units in the petroleum activity (FPSOs and FSOs) on the Norwegian Continental Shelf. Reported incidents are summarised with a focus on the period 2000 to 2019. The incidents include cracks, dents, corrosion, turret incidents, green water, position keeping systems, stability and ballasting, collisions and incidents related to the offloading systems as reported by operators and shipowners to the PSA.
A summary of the reported damages and incidents are discussed with respect to common causes based on available data. The importance and the possible consequences of such incidents are further discussed.
Characterization of the Rheological Behavior of Drilling Fluids
Authors: Cayeux Eric , Leulseged Amare 
Published: December 2020

Abstract
It is nowadays well accepted that the steady state rheological behavior of drilling fluids must be modelled by at least three parameters. One of the most often used models is the yield power law, also referred as the Herschel-Bulkley model. Other models have been proposed like the one from Robertson-Stiff, while other industries have used other three-parameter models such as the one from Heinz-Casson.
Some studies have been made to compare the degree of agreement between different rheological models and rheometer measurements but in most cases, already published works have only used mechanical rheometers that have a limited number of speeds and precision. For this paper, we have taken measurements with a scientific rheometer in well-controlled conditions of temperature and evaporation, and for relevant shear rates that are representative to normally encountered drilling operation conditions. Care has been made to minimize the effect of thixotropy on measurements, as the shear stress response of drilling fluids depends on its shear history. Measurements have been made at different temperatures, for various drilling fluid systems (both water and oil-based), and with variable levels of solid contents.
Also, the shear rate reported by the rheometer itself, is corrected to account for the fact that the rheometer estimates the wall shear rate on the assumption that the tested fluid is Newtonian. A measure of proximity between the measurements and a rheological model is defined, thereby allowing the ranking of different rheological behavior model candidates. Based on the 469 rheograms of various drilling fluids that have been analyzed, it appears that the Heinz-Casson model describes most accurately the rheological behavior of the fluid samples, followed by the model of Carreau, Herschel-Bulkley and Robertson-Stiff, in decreasing order of fidelity.
The Status of Arctic Offshore Pipeline Standards and Technology
Authors: Paulin Mike , Caines Jonathan , Davis Amy , DeGeer Duane , Cowin Todd 
Published: December 2020

Abstract
Offshore pipelines in an Arctic or ice-covered environment face unique challenges different from traditional subsea pipeline design. In 2018, Intecsea as lead consultancy delivered a report to the US Bureau of Safety and Environmental Enforcement (BSEE) Alaska Region which provided a comprehensive review and gap analysis of the Status of Arctic Pipeline Standards and Technology. The objective of this study was to provide BSEE with a comprehensive review and gap analysis of current offshore Arctic pipeline design standards, codes and regulations pertaining to design and development of offshore pipelines in the Arctic, and to report on the state-of-the-art and emerging technologies for offshore pipelines in Arctic applications. Project development information from nine existing offshore Arctic pipelines in the U.S., Canada, and Russia was summarized, as well as guidelines and industry best-practice for monitoring and leak detection.
This paper provides an overview of the results of this study; what offshore Arctic-specific pipeline design and construction challenges may entail, how they have been overcome in past projects, perceived gaps in regulations, and technology advancements that may help with future developments. This paper also summarizes the results of a comprehensive review and gap analysis of Arctic pipeline standards, assessment of the suitability of a single-walled versus pipe-in-pipe system for Arctic applications and presents information on some of the advancements in pipeline design, installation, operations and repair solutions that may be applicable to an Arctic environment.
Modelling Wave-Current-Turbulence Interactions for Tidal Energy Applications
Authors: Venugopal Vengatesan , Vögler Arne 
Published: December 2020

Abstract
This paper presents the nature of turbulence parameters produced from 3-dimensional numerical simulations using an ocean scale wave-tidal current model applied to tidal energy sites in the Orkney waters in the United Kingdom. The MIKE 21/3 coupled wave-current model is chosen for this study. The numerical modelling study is conducted in two stages. First, a North Atlantic Ocean large-scale wave model is employed to simulate wave parameters. Spatial and temporal wind speeds extracted from the European Centre for Medium Range Weather Forecast (ECMWF) is utilised to drive the North Atlantic wave model. Secondly, the wave parameters produced from the North Atlantic model are used as boundary conditions to run a coupled wave-tidal current model. A turbulence model representing the turbulence and eddy viscosity within the coupled model is chosen and the turbulence kinetic energy (TKE) due to wave-current interactions are computed. The coupled model is calibrated with Acoustic Doppler and Current Profiler (ADCP) measurements deployed close to a tidal energy site in the Inner Sound of the Pentland Firth.
The model output parameters such as the current speed, TKE, horizontal and vertical eddy viscosities, significant wave height, peak wave period and wave directions are presented, and, their characteristics are discussed in detail.
Occurrence Frequency of a Triple Rogue Wave Group in the Ocean
Authors: Bitner-Gregersen Elzbieta M. , Gramstad Odin , Magnusson Anne Karin , Sames Pierre C. 
Published: December 2020

Abstract
At 18:20 November 30, 2018, a triple rogue wave group was recorded in the central North Sea. These three consecutive rogue waves, subsequently called “Justine Three Sisters”, were recorded at a single point by a SAAB REX radar. The Norwegian Meteorological Institute’s operational wave forecast model and WAMOS marine radar’s measurements show that they appeared in a crossing sea condition with angle between wind sea and swell being 60 degrees, with swell energy much lower than the wind sea energy but with approximately the same peak frequency. We use the nonlinear wave model HOSM (Higher Order Spectral Method) to investigate frequency of occurrence of such an event in the ocean. Input to the simulations has been a wave frequency-directional spectrum generated by the operational wave forecast model of the Norwegian Meteorological Institute having 4 km resolution. The investigations show that occurrence of three consecutive rogue waves at a single point is a very seldom event in the ocean, which can, however, be reproduced in time domain HOSM simulations if sufficient number of realizations is performed. With the HOSM model being able to capture essential physics of ocean waves, we can assume to predict occurrence frequency from simulations. The study demonstrates also the effect of sampling variability on sea surface elevation and illustrates limitation of single point measurements, using the sea state in which “Justine Three Sisters” occurred as an example. Importance of using spacetime statistics in description of ocean waves as well as in design and operations of marine structures is also discussed.