bluuebunny/crossref_metadata_2025_split huggingface dataset:
Theory of Nonlinear Fourier Analysis: The Construction of Quasiperiodic Fourier Series for Nonlinear Wave Motion
Authors: Osborne Alfred R. 
Published: December 2020

Abstract
I give a description of nonlinear water wave dynamics using a recently discovered tool of mathematical physics I call nonlinear Fourier analysis (NLFA). This method is based upon and is an application of a theorem due to Baker [1897, 1907] and Mumford [1984] in the field of algebraic geometry and from additional sources by the author [Osborne, 2010, 2018, 2019]. The theory begins with the Kadomtsev-Petviashvili (KP) equation, a two dimensional generalization of the Korteweg-deVries (KdV) equation: Here the NLFA method is derived from the complete integrability of the equation by finite gap theory or the inverse scattering transform for periodic/quasiperiodic boundary conditions. I first show, for a one-dimensional, plane wave solution, that the KP equation can be rotated to a solution of the KdV equation, where the coefficients of KdV are now functions of the rotation angle. I then show how the rotated KdV equation can be used to compute the spectral solutions of the KP equation itself. Finally, I write the spectral solutions of the KP equation as a finite gap solution in terms of Riemann theta functions. By virtue of the fact that I am able to write a theta function formulation of the KP equation, it is clear that the wave dynamics lie on tori and constitute parallel dynamics on the tori in the integrable cases and non-parallel dynamics on the tori for certain perturbed quasi-integrable cases. Therefore, we are dealing with a Kolmogorov-Arnold-Moser KAM theory for nonlinear partial differential wave equations. The nonlinear Fourier series have particular nonlinear Fourier modes, including: sine waves, Stokes waves and solitons. Indeed the theoretical formulation I have developed is a kind of exact two-dimensional “coherent wave turbulence” or “integrable wave turbulence” for the KP equation, for which the Stokes waves and solitons are the coherent structures. I discuss how NLFA provides a number of new tools that apply to a wide range of problems in offshore engineering and coastal dynamics: This includes nonlinear Fourier space and time series analysis, nonlinear Fourier wave field analysis, a nonlinear random phase approximation, the study of nonlinear coherent functions and nonlinear bi and tri spectral analysis.
Wellhead Fatigue Analysis Considering Global and Local Effects
Authors: Rezende Filipe A. , Lopes Guilherme K. , Sousa Fernando J. M. , Sousa José R. M. , Fonseca Carlos E. , Percy Joseir G. 
Published: December 2020

Abstract
During drilling operations, the wellhead system and top hole casings shall be designed to support dynamic loads from the connected riser through the BOP stack/LMRP. As dynamic motions are associated to stress variations, fatigue becomes a major concern for designers.
The accumulation of damage at the wellhead and close regions is dependent on several aspects, such as the riser components, the interactions soil-conductor and conductor-surface casing, and of course the environmental conditions. Consequently, fatigue analysis involves complex numerical models and requires the simulation of a huge number of loading cases.
The present paper aims to estimate the fatigue damage at critical components of the top hole casings and at the wellhead. Two different approaches were investigated. In the first, a global model is analyzed in the time domain (TD), and the Rainflow cycle counting method is used to calculate fatigue damage. The global model includes the drilling riser, wellhead, casings, and interactions between components and with soil. In the second, the same model is analyzed in the frequency domain (FD), and the Dirlik method is used to calculate fatigue damage. Additionally, to allow a better evaluation of stresses at complex geometry regions, forces and moments obtained using the TD methodology were combined with load-to-stress transfer functions, defined by means of a local model and symbolic regression (SR) analysis. The local model includes a detailed 3D model of the pressure housings, and soil-to-casing interaction.
The obtained results indicate that the pressure housings are not sensitive to fatigue, and also that the analyses performed are feasible, contributing to reduce computational costs in wellhead fatigue assessments.
Nanoparticles As Promising Additives to Improve the Drilling of Egyptian Oil and Gas Fields
Authors: Mady Ahmed , Mahmoud Omar , Dahab Abdel Sattar 
Published: December 2020

Abstract
Egypt is both one of the major oil-producing non-OPEC countries and one of the oldest energy producers in the Middle East. Recently, the Egyptian government have signed several agreements for the exploration of oil and gas in several provinces/regions including; the Mediterranean, the Western Desert, the Nile Delta, and the Gulf of Suez. Petroleum companies have given great attention to Egypt’s new discoveries such as Zohr Gas Field and Nour exploration prospect. Successful drilling operations to reach the oil and gas targets depends strongly on the effectiveness of the drilling fluid (mud). It can be considered as the heart of the drilling process, where they are used to fulfil several valuable functions.
Drilling fluid technology is one of the most targeted and developed technologies worldwide. Several studies have examined the use of various types of nanoparticles (NPs) to enhance the properties and improve the performance of muds. NP can be defined as a simple particle structure with a size in the range of nanometers. The effectiveness of NPs can be accredited to their small size and high surface-area-to-volume ratio. Using NPs showed promising enhancements on the rheological and filtration characteristics as well as thermal stability and carrying capacity of the drilling fluid. Moreover, adding NPs to the drilling mud was found to minimize the shale permeability and thus, promote wellbore stability. The swelling and collapse of shale formations is expected under drilling with water-based mud, which might complicate the drilling operation.
In the present work four types of NPs (nanosilica, nanoaluminium, nanotitanium, and nano copper oxide) were tested as promising additives to improve the characteristics of KCL-Polymer mud, which is mainly used to drill shaly formations. The impact of NPs-type, -size, and -concentration were thoroughly investigated using standard viscometer and API filter press. The results showed higher potential of nanotitanium and nanoaluminium to enhance the mud properties when used at small concentrations (0.3–0.5 wt.%).
This research paper discusses a latest application and presents the most valuable findings concerning the efficient use of NPs in the drilling fluid industry. On this basis, different recommendations are stated, which might help researchers to better understand NPs’ functionality in this area of application and promote using NPs-based drilling muds as cost-effective and environmental-friendly fluids to drill the Egyptian oil and gas wells.
Environmental Stress Cracking on PVDF: ISO 22088-3 (Preliminary Data)
Authors: Freitas Rafael Luis , Costa Celio , Chaves Erica , Teixeira Sylvia 
Published: December 2020

Abstract
This study presents the effect of bending strain upon the structure and mechanical behavior of poly(vinylidene fluoride) (PVDF). Using the ISO 22088-3 Bent Strip Method, the PVDF samples were submitted to 3.5 % and 7.0 % strain in bending for 21 days. The unstrained and strained samples were characterized by Fourier Transformed Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) and tensile tests at 23 °C.
The applied bending strain of 3.5% and 7.0 % resulted permanent deformation for both strains applied, which curvature was very close to 3.5% and 7%. The 7% strained samples showed stress-whitening, most likely due to the well-known cavitation phenomenon; while 3.5% strained samples no cavitation was seen.
Infrared spectroscopy analysis indicates a mechanically induced α to β crystalline phase transition on the outer fibers as the bending strain increases. DSC measurements showed no change on crystallinity volume fraction and melting temperature as deformation increased. The DMA showed a shift on glass transition temperature (TG) to higher temperatures and the Elastic Modulus decreased as the bending strain increased for all temperatures.
Reverse deformation had to be applied on the plastically deformed bending samples in order to straight them out to do the tensile tests. The tensile properties measured at room temperature showed the Young’s Modulus and Yield Stress decreasing as the applied bending strain increases. On the other hand, the yield strain rose as the bending strain increased.
Numerical Evaluation of Crack in Polyvinylidene Fluoride (PVDF)
Authors: Pereira Ingrid Cristina S. , da Costa Neto Celio A. , Sousa José Renato M. , Chaves Erica G. , Teixeira Sylvia 
Published: December 2020

Abstract
Polyvinylidene fluoride (PVDF) is an engineering thermoplastic having a high degree of sensibility to crack, which affects long-term mechanical behavior. This study evaluates the crack-sensitive of PVDF for one commercial-grade through the development of a numerical model.
Firstly, tensile tests using DIC were performed on both uncrack and pre-crack specimens to get experimental tensile as DIC-displacement, displacement-control, and load data. For pre-crack specimens, it was proposed two values of depth: 1.0 and 1.5 mm, opened by razor blade. All specimens were uniaxial tests at 23°C under 5 mm/min. Secondly, tensile tests using extensometer were implemented for uncrack samples to determine material parameters for calibration of the numerical model and comparison with DIC-displacement. Finally, a numerical model based on the FE was implemented using ANSYS-student that inputs PVDF’s material properties, which considered the elastic-plastic behavior in simulation tests.
The PVDF demonstrated significant crack sensitivity, as it can be seen in experimental and numerical data. And, the numerical model developed based on MKHP was successfully agreement against experimental data obtained by Blue Hill 3 software. Therefore, the results allowed us to observe that pre-crack acts as a stress concentration and the numerical model got well simulates this influence on the PVDF mechanical behavior.
Assessment of Global Wave Datasets for Long Term Response of Ships
Authors: de Hauteclocque Guillaume , Zhu Tingyao , Johnson Michael , Austefjord Håvard , Bitner-Gregersen Elzbieta 
Published: December 2020

Abstract
Ship structure design process begins with the evaluation of environmental conditions a ship is expected to withstand. This paper deals with wave data, and more specifically with global wave dataset that can be used to evaluate waves encountered by a ship along its lifetime track. Benchmark of existing global hindcast datasets is performed, having in mind its use to assess extreme ship response. The presented comparison is thus not limited to the mean and standard deviation but includes also extreme significant wave height. Wave period that can significantly modify ship behaviour is also investigated. Five different hindcast datasets are selected for the present analysis and compared with buoy and altimeter data. Area of interest is region far from the coast, and more specifically the North-Atlantic, which is currently considered the most severe for sailing ships. In such area, the global wave models are expected to provide decent results (as opposed to near shore area where a local mesh would be required). Two datasets are provided by ECMWF (ERA5 and ERA-Interim) that uses WAM model, two others are from NOaAA/NCEP and Ifremer and use WaveWatchIII, finally WAV-ERYS dataset is provided by the Copernicus program, and uses MFWAM. Some differences are observed in the wave parameters projected by different models, especially on extremes. Reasons for this scatter are briefly discussed, but more emphasis is put on the consequence for ship response. This work has been performed within IACS (International Association of Classification Societies) framework.
Umbilical Fatigue Analysis for a Wave Energy Converter
Authors: Ballard Billy , Yu Yi-Hsiang , Van Rij Jennifer , Driscoll Frederick 
Published: December 2020

Abstract
Unique umbilical designs for wave energy converters (WECs), including the ability to handle significantly larger motions and loads over long deployments, are often required when conventional marine umbilical designs for offshore oil and gas and offshore wind may not meet the design and cost needs of wave energy technologies. This study details a fatigue analysis of a dynamic power umbilical attached to a two-body floating point absorber WEC system, using the sea states provided for the PacWave testing facilities. The 6 degrees of freedom motion time history for the WEC was simulated, and the motions of the attachment point for the umbilical on the WEC and respective sea states were used to analyze the dynamic motions and fatigue of the connected power umbilical to predict the fatigue life. The results show that the fatigue damage observed is more significant in shallow water, and extensive fatigue damage may occur because of the larger curvature response of the umbilical. The umbilical configurations departing at 90 deg off incoming waves were found to have the highest fatigue life attributed to less extension or compression of the umbilical. However, additional bend stiffener/limiter features may need to be incorporated into the buoyancy section and touchdown regions to minimize curvature-induced fatigue.
Digital Technologies and Standardization for Next Generation of FPSO Hulls
Authors: Torres de Mattos Bernardo , de Souza Lima Figueiredo Eduardo , Queiroz Jackson Luan 
Published: December 2020

Abstract
New fields development deadlines are growing short every day and FPSO projects shall be adapted to sustain these new patterns, even though actual process plants are becoming larger and more complex. FPSO projects critical path is the hull construction and changes are being made to shorten the duration of this process. For this to be feasible, hull project must be standardized to fit various topside configurations and any changes made must be absorbed as quickly as possible. This requires the use of innovative solutions and digital technologies to reduce design time. The core of these solutions is the modelling of the hull digital twin during the basic design phase with a high level of structural definitions that only happen during detailed engineering phase.
This paper presents some initiatives that results in a more consistent design and on a desktop-based virtual reality model that can be used to accelerate fabrication during construction and assembly phases. Furthermore, the way of doing hull basic design is being changed.
Safety Analysis of Liquefied Natural Gas Bunkering and Simultaneous Port Operations for Passenger Ships
Authors: Iannaccone Tommaso , Jeong Byongug , Cozzani Valerio , Zhou Peilin 
Published: December 2020

Abstract
The use of liquefied natural gas (LNG) has been recognized as an effective alternative fuel for marine propulsion, evidently, a growing number of vessels, including passenger ships, is already running on such a fuel. While LNG bunkering can be performed in several ways, depending on transferred volumes and managerial considerations, the time spent for LNG bunkering is regarded to be a key factor to ensure the cost-effectiveness of such operation, since a minimization of bunkering duration at the berth will make port infrastructures available for more vessels. As a result, passenger embarkment is simultaneously conducted with ship bunkering, which may increase the potential risk to individuals both onboard and nearby. Given this background, this paper is to investigate the potential risk of passenger vessels with the identification of credible scenarios for port operations that can be carried out simultaneously with LNG bunkering. An approach of quantitative risk assessment is applied to determine the risk levels pertinent to proposed scenarios. For frequency analysis, the technique of the fault tree analysis is adopted to integrate the influence of human error and management policy to the likelihood of unwanted events. Consequence analysis is conducted in aids of a commercial software to simulate the impact of LNG dispersion and fires. Research findings have shown that simultaneous operations have a negative impact both on frequency and consequence of accidental scenarios arising from LNG bunkering, taking the risk beyond lower acceptance criteria. Finally, a quantification of the risk increase is proposed to help stakeholders identify criticalities and reduce the risk contributions of simultaneous operations.
Evaluation of Flow Characteristics in an Oil-Water Separator Using Computational Fluid Dynamics
Authors: Potter Terry , Acharya Tathagata 
Published: December 2020

Abstract
Multiphase separators on production platforms are among the first equipment through which well fluids flow. Based on functionality, multiphase separators can either be two-phase that separate oil from water, or three-phase that separate oil, natural gas, and water. Separator performances are often evaluated using mean residence time (MRT) of the hydrocarbon phase. MRT is defined as the amount of time a given phase stays inside the separator. On field, operators usually measure MRT as the ratio of active volume occupied by each phase to the phase volumetric flowrate. However, this method may involve significant errors as the oil-water interface height is obtained using level controllers and the volume occupied by each phase is calculated assuming the interface can be extrapolated from the weir back to the separator inlet. In this study, authors perform computational fluid dynamics (CFD) on a two-phase horizontal separator to evaluate MRT as a function of varying water volume flowrates (water-cut) in a mixture of water and oil. The authors use residence time distributions (RTD) to obtain MRT at each water-cut — a method that results in significantly more accurate results than the regular method used by operators. The numerical model is developed with commercial software package ANSYS Fluent. The code uses the Eulerian multiphase model along with the k-ε turbulence model. The simulation results show agreement with experiments performed by previous researchers. Additional simulations are performed to assess the effect of various separator internals on separator performance. Simulation results suggest that the model developed in this study can be used to predict performances of two-phase liquid-liquid separators with reasonable accuracy and will be useful towards their design to improve performances under various inlet flow conditions.
Seal Tight Endfitting and Means to Identify Annulus Condition for Pre-Salt Flexibles in Brazil
Authors: Brandão M. O. , Pires F. , Benirschke C. , Almeida E. , Iecker T. , Roberts A. 
Published: December 2020

Abstract
The development of Brazil Offshore fields using flexible pipes took the advantage of the possibility to move around lines, anticipate the production and postpone the decision of where exactly the development phase wells should be placed, making the drilling campaign easier, cheaper and faster. For the Pre-Salt fields, mainly in Santos Basin, it is observed high concentrations of H2S and CO2, two major impact contaminants for the metallic layers of the flexible pipe. A new failure mode by SCC is the most concerning one and have several approaches either focused on the installed fleet or focused in the next pipes to be delivered. SCC is a condition that induces cracks in the pipes metallic layers and need three elements to happen: water, stress and susceptible material. If one of these three elements is suppressed, the phenomena is not to happen.
This paper will cover and present a design of a seal tight end fitting also with capabilities to be seal tested from the shop during the factory acceptance test and further means to identify if the flexible pipe section is flooded or dry visually, using ROV This information is key for the integrity management of the flexible pipes applied to pre salt fields to assure the most extent of the service life.
Effect of Sinusoidal Oscillatory Flow on a Vertical Wall-Mounted Cylinder
Authors: Jang HaKun , Ozdemir Celalettin Emre , Tyagi Mayank , Liang Jun-Hong 
Published: December 2020

Abstract
The purpose of this study is to numerically investigate the bed shear stress and near-bed mixing due to coherent vortex structures in the vicinity of a vertically wall-mounted circular cylinder subject to an imposed finite-depth oscillatory sinusoidal flow. Previous studies reveal that the Keulegan–Carpenter (KC) number influences the formation of lee-side wake vortex structures as well as the horseshoe vortex in front of a cylinder. Therefore, parametric studies in a moderately wide range of KC from 5 to 20 are numerically performed.
In the present study, Direct Numerical Simulation (DNS) is conducted using the open-source software, OpenFOAM, that solves the three-dimensional unsteady incompressible Navier-Stokes equations using finite volume method. Nondimensional parameters used in the simulations are carefully chosen to represent the real physics. The numerical solutions are first validated using an analytical solution for the oscillating Stokes flow and the results are then systematically and quantitatively compared with the experimental measurements. The results show that the lee-side wake is significantly influenced by KC, and distinctive types of the lee-side wake are generated and classified based on KC. It is also found that both KC and the ratio of the thickness of the Stokes boundary layer to the water depth are heavily associated with the stability of the lee-side wake. In addition, the simulated size and lifespan of the horseshoe vortex agree well with the experimental data.
Analysis of the Motion Characteristics of Large Non-Metallic Composite Cages
Authors: Zhao Lin , Pan Fei , Li Qian , Jiang Zhen 
Published: December 2020

Abstract
A novel large reinforced HDPE cage system applied for the deep-sea aquaculture is proposed in this paper. This new structure is targeted at two main challenges facing by the deep-sea aquaculture. First, the deep-sea operation condition is much more complicated than in near shore area; second, the dynamic response and structure requirement of large-scale cages, which can be up to 80–100m in diameter and are significantly different to that of small HDPE cages. This study tackled with these two challenges by using the reinforced HDPE material and nested floating frame structure. In order to examine the integrity, safety and structure performance of this presented structure, the dynamic response of the structure subject to various working conditions are numerically simulated and analyzed in this paper. Simulation results of the new structure are compared to that of the traditional cage regarding the cage dynamic displacement, maximum strain/stress and net declination angle. The deformation results demonstrated that the maximum strain and stress on the cage collar of the new structure is much smaller than that of traditional design, and thus the new design can greatly reduce the local deformation of the cage collar and the declination angle to ensure the structure safety in severe sea conditions. The internal nested float frames can also be arranged with nets to make better use of the breeding space.