bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lessons Learned From Operational Integrity of HP/HT Deepwater Pipelines
Authors: Cardoso Carlos O. , Solano Rafael F. , Antunes Bruno R. 
Published: November 2019

Abstract
This paper addresses the results from a monitoring inspection as part of Petrobras regular plane of inspection of rigid pipelines (PIDR) and numerical Finite Element analysis (FEA) of two parallel HP/HT subsea pipelines operating in Brazilian deepwater subjected to lateral buckling and walking behaviors. The results obtained from inspection and numerical reanalysis furnishes important feedback for the integrity management of the two pipelines, reducing potential risks and lessons learned for future projects.
Deepwater pipelines submitted to high pressures and temperatures (HP/HT) are susceptible to global buckling due to axial compressive load. To guarantee pipeline and equipment’s integrity frequently is necessary to relieve high stresses and strains at buckle apex as well as to mitigate end expansion. Thus, the two parallel HP/HT pipelines were designed with single and double sleepers to trigger buckles at pre-determined locations and an anchoring system to prevent pipeline walking. Another important design aspect was to avoid undesirable buckles at the several crossings along the pipeline route applying a special device with stoppers to lock lateral displacements.
During a programmed inspection as part of regular Petrobras pipeline integrity program of rigid pipelines (PIDR), it has been verified that some double sleepers didn’t work as foreseen in design. Otherwise, some unplanned buckles on soil have been formed along the two pipelines changing the buckle apex stress levels and end expansions foreseen in detailed design.
In order to understand buckle formation behavior and guarantee long-term integrity of the HP/HT pipelines a Multi-Beam Echosounder Survey (MBES) was conducted in 2016 to build a representative Finite Element (FE) model. The temperature and pressure gradients from steady state and transient conditions were obtained from flow assurance simulations based on monitored platform operational historic data. The FE model was calibrated with buckle shapes and end displacements to assess pipeline behavior and its long-term integrity for load scenarios different from original design.
Nonlinear Evolution of a Steep, Focusing Wave Group in Deep Water Simulated With OceanWave3D
Authors: Barratt Dylan , Bingham Harry B. , Adcock Thomas A. A. 
Published: November 2019

Abstract
Steep, focusing waves can experience fast and local nonlinear evolution of the spectrum due to wave-wave interactions resulting in energy transfer to both higher and lower wavenumber components. The shape and kinematics of a steep wave may, thus, differ substantially from the predictions of linear theory. We have investigated the role of nonlinear interactions on group-shape for a steep, narrow-banded, directionally-spread wave group focusing in deep water using the fully-nonlinear potential flow solver, OceanWave3D. Exact second-order correction of the initial conditions has been implemented together with a novel third-order approximate correction based on a Stokes-type formulation for surface elevation combined with a scaling-argument for the third-order velocity potential. Four-phase separation reveals that the third-order scheme provides a good estimate for the third-order superharmonics. A quantitative assessment of numerical error has also been performed for the spatial and temporal discretization, including energy conservation, a reversibility check and validation against previous simulations performed with a higher-order spectral (HOS) code. The initially narrow-banded amplitude spectrum exhibits the formation of sidelobes at angles of approximately ±35° to the spectral peak during the simulated extreme wave event, occurring in approximately 10 wave periods, with a preferential energy transfer to high-wavenumber components. The directional energy transfer is attributed to resonant third-order interactions with a discussion of the engineering implications.
Large Amplitude Time Domain Seakeeping Simulations of KVLCC2 in Head Seas Taking Into Account Forward Speed Effect
Authors: Pollalis Christos , Hizir Olgun , Boulougouris Evangelos , Turan Osman 
Published: November 2019

Abstract
Time-domain analysis is important for the development of performance-based criteria for the intact stability of ship (level 3 criteria in the 2nd Generation Intact Stability Criteria). It can be implemented to assess directly the vulnerability of ships against various modes of intact stability failure and ensure a sufficient level of safety. In this context, ELIGMOS, a novel time domain simulation code combining a maneuvering model and a seakeeping model, is under development. As the maneuvering model has been the subject of previous paper, the seakeeping part is presented herein and validated in terms of linear and nonlinear vertical motions in head seas. Heave and pitch motions are augmented near the resonant periods, testing the ability of the numerical tool to capture accurately the ship’s behaviour, as it plays a dominant role for her direct stability assessment afterwards. Surge motion is considered uncoupled and it is excluded from the system of equations, keeping the forward speed constant. Comparison regarding the seakeeping performance of KVLCC2 is presented against experimental results and results obtained by a 3D-potential flow, frequency domain software as well. Ship’s geometry is modelled by means of quadrilateral panels whilst radiation forces were incorporated by means of memory functions by adopting the well-known concept of convolution integrals. The ability of ELIGMOS to capture the effect of geometrical nonlinearities on the vertical motions is demonstrated through preliminary simulation of large amplitude motions of a C11-class containership.
QUAD Lift: Enabling Lifting of Larger Integrated Topsides
Authors: van Winsen Ivan , van Dijk Radboud R. T. 
Published: November 2019

Abstract
Over the past years Heerema Marine Contractors (HMC) has developed the QUAD lift method enabling the lift of single piece objects up to 30,000mT. This development is driven by the demand from our clients to install or remove larger topsides, both in size and weight. Lifting with two (or more) vessels simultaneously has been done before. Unique is that the QUAD lift operation is performed on DP. Two vessels lifting the topsides from opposite sides, instead of lifting the topsides from one side, creates the possibility for increasing dimensions and layouts of the topsides.
The connection of the two crane vessels to the lifted object means that all actions taken on one ship influences not only the lifted object but also the second crane vessel. This requires a clear communication plan and full understanding of the complete system such as the DP behaviour, stability, ballast operations and crane operations. During a QUAD lift operation the Dynamic Positioning (DP) system plays an important role. Therefore in the development process the DP-system was modified to ensure stability of the DP system throughout the entire operation. A systematic series of tests was performed to gain insight in the DP behaviour of both vessels with the goal to ensure a synchronous move with two vessels connected in a QUAD lift configuration.
In 2018 a demonstration QUAD lift is performed using Balder and Thialf to show HMCs commitment to perform this kind of operations in the future. The QUAD lift demonstration lift was prepared and executed in the Heerema Simulation Center (HSC) with the offshore crew in preparation of the actual offshore execution.
This paper will address the steps followed to prepare for the offshore execution, describing DP behaviour, vessel coupled dynamics and human factor aspects. Based on the offshore experience validation was performed on the numerical tools used in the preparation.
Research and Development of a Self-Walking Vertical Mining System Using DTH Drilling Unit and the Scale Model Test
Authors: Watanabe Yoshiyasu , Watanabe Keisuke , Suzuki Hideyuki , Ooshima Teruo , Tsukamoto Yoshiaki 
Published: November 2019

Abstract
Traditional subsea mining systems use a heavy subsea crawler, which has a big drill and scrapes the mineral deposit horizontally and have limitations of seafloor inclination, roughness and softness. Those traditional systems also have issues from operational and economical points of view. Furthermore, traditional on-board drilling machines and seabed drilling machines are used for core sampling by drilling to analyze mineral contents of seafloor deposits at the stage of mineral resource estimation before the production but operational and economical efficiencies are required to those traditional systems as well.
The objective of this research is to develop an innovative Self-Walking Vertical Mining System (SW-VMS) that overcomes these issues. The system is a fully submerged eight-legged jack up platform and is able to walk autonomously on a rough, soft and inclined seafloor. The SW-VMS can be used both as the mining system to mine seafloor deposits and as the sample drilling system to analyze mineral contents in-situ and on-land efficiently before the mining with a DTH drilling unit.
This paper introduces the detail of the SW-VMS as the mining system at first and then introduces the concept of the SW-VMS as the sample drilling system and finally the results of the scale model test of the SW-VMS on-land are shown. The scale model test has been carried out to confirm the walking ability of the SW-VMS from the structural and autonomous control points of view. The scale of the test model is approximately 1/40 of the preliminary design of the SW-VMS which has been already completed. The test consists of test cases of walking on a flat foundation, on a flat foundation including partially soft foundations and on inclined foundations of up to 45 degrees.
Weathervane Performance and Stability of Single Point Moored FOWTs Under Wind-Current Coexisting Field
Authors: Srinivasamurthy Sharath , Hashimoto Kazuki , Iijima Kazuhiro , Nihei Yasunori 
Published: November 2019

Abstract
The objective of this study is to understand the weathervane performance and stability of FOWTs moored to SPM systems under wind and current coexisting field. Two types of FOWT systems, a semi-submersible and a spar (1/200 scale) are designed and manufactured based on Froude’s scaling law. A series of scaled model experiments are conducted and compared during wind-current coexisting field in a circulating water tank at Osaka Prefecture University, Osaka, Japan. Weathervane performance is evaluated under various conditions of wind and current. It is found during experiments that the weathervane performance of the SPM-FOWT systems is acceptable in rated wind and slow current condition. However, in the rated wind and high speed current condition, the weathervane performance is found to be not acceptable and unstable oscillation is observed. A numerical program is also developed to understand the behavior using the maneuvering equations. Further, attempts are made to understand the stability of SPM-FOWT systems based on Eigenvalue analysis.
Investigation on Mechanical Properties of Fiberglass Reinforced Flexible Pipes Under Bending
Authors: Gao Yifan , Jin Shan , Cheng Peng , Han Peihua , Bai Yong 
Published: November 2019

Abstract
Fiberglass reinforced flexible pipe (FRFP) is a kind of composite thermoplastic pipe, which has many advantages compared to boned flexible pipes. This paper describes an analysis of the mechanical behavior of FRFP under bending. The bending behavior of FRFP was investigated by experimental, analytical and numerical methods. Firstly, this paper presents experimental studies of three 10-layer FRFP in a typical four-point bending test. Curvature-bending moment relations were recorded during the test. Then, based on the nonlinear ring theory and the principle of virtual work, a simplified method was proposed to study the mechanical behavior of FRFP. In addition, a finite element model (FEM) including reinforced layers and high density polyethylene (HDPE) layers was established to simulate the HDPE layers and reinforced layers, respectively. The result of Curvature-bending moment relations obtained from three methods agree well with each other, which proves that the simplified analytical model and FEM are accurate and reliable. The conclusions of this paper could be useful to manufacturing engineers.
Three-Dimensional Direct Numerical Simulations of Flows Past an Inclined Cylinder Near a Plane Boundary
Authors: Ji Chunning , Zhang Zhimeng , Xu Dong , Srinil Narakorn 
Published: November 2019

Abstract
Flows past an inclined cylinder in the vicinity of a plane boundary are numerically investigated using direct numerical simulations. Parametric studies are carried out at the normal Reynolds number of 500, a fixed gap ratio of 0.8 and five inclination angles (α) ranging from 0° to 60° with an increment of 15°. Two distinct vortex-shedding modes are observed: parallel (α ≤ 15°) and oblique (α ≥ 30°) vortex shedding modes. The occurrence of the oblique vortex shedding is accompanied by the base pressure gradient along the cylinder span and the resultant axial flows near the cylinder’s base. The drag and lift coefficients decrease from the parallel mode to the oblique mode, owing to the intensified three-dimensionality of the wake flows and the phase difference in the vortex-shedding along the span. The Independent Principle (IP) is valid in predicting the hydrodynamic forces and the wake patterns when α ≤ 15°, and IP might produce unacceptable errors when α ≥ 30°. Compared to the mean drag force, the fluctuating lift force is more sensitive to the inclination angle. The IP validity range is substantially smaller than that for flows past a wall-free cylinder.
Visualization Study on Plugging Mechanism of Fibers and Particles in Rough and Tortuous Fracture
Authors: Fan Fan , Zhou Fujian , Yuan Lishan , Yang Xuda 
Published: November 2019

Abstract
Temporary plugging technology are widely used in unconventional exploitation, for it can produce more fracture thus to enhance oil recovery, however, it is still unclear how the plugging is formed and the diverters migrate in the hydraulic fracture. In this work, a self-developed visualization fracture system is set up. And the plugging mechanism of guar-based fracturing fluid with temporary plugging materials is visualized in a rough laboratory-scale fracture. Impacts of parameters on plugging process like particle concentration,fibre concentration, and fracture width are systematically investigated.Through a series of comparative experiments, it is found that the plugging process was triggered by fibre, they form nets to capture particles, then the nets with particles roll bigger and bigger like snowballs,while the nets can not capture particles will be broken in higher pressure. Comparative results indicate that the sealing effect of the same forum for wider fracture will be worse, replacing with the larger particles is more effective than increasing the amount of diverter; Increasing particles can increase sealing strength while increaing fibres can shorten the sealing formation time; Using 1% fiber only, the 3mm-wide fracture can be plugged but it cost much time and the sealing is not so firm. While using 1% particles only, a particle dump forms instead of a sealing layer. For field operation, it is suggested that (1) For wider fracture, use bigger particle is more effective than add more fibre and particles; (2) Particle should be added later than fibre; (3) To increase sealing pressure and enhance efficiency, the ratio of fibre and particles should be around 2:1.
CFD Simulation of a Twin-Screw Ship Self-Propulsion Using DDES-Overset Method
Authors: Wang Jianhua , Wan Decheng 
Published: November 2019

Abstract
Rotating propellers and moving rudders are necessary for the simulation of free running ship with the purpose of resolving detailed flow interaction. In the present work, CFD method is used to numerically investigate self-propulsion behavior for a twin-screw fully appended ship. The simulation conditions are following the experiment performed at IIHR. The benchmark ship model ONR Tumblehome is used for all the numerical computations. Overset grids are used to fully discretize the ship hull, twin propellers and rudders. Self-propulsion simulation is carried out using a PI controller to achieve target ship speed of Fr = 0.20 in calm water and the ship model is free to trim and sinkage. All the numerical calculations are carried out by the in-house CFD solver naoe-FOAM-SJTU. Unlike most previous studies based on RANS method, the present self-propulsion simulations adopt the Delayed Detached-Eddy-Simulation (DDES) approach to resolve the complex flow around ship hull, propeller and rudder. The main parameters of the self-propulsion as well as flow visualizations are presented. The predicted results are compared with previous RANS data and the available experimental data. The comparison with the experiment is satisfactory and the flow field shows that the present DDES-overset method can give more flow details for the self-propulsion condition.
Extending Integrability of Nonlinear Water Wave Equations: Nonlinear Fourier Analysis of Breather Packets and Rogue Waves at Higher Order
Authors: Osborne Alfred R. 
Published: November 2019

Abstract
I suggest a formulation to give approximate spectral solutions of nonintegrable, nonlinear wave equations in 2+1 dimensions. Nonintegrable systems such as the 2+1 NLS, Dysthe and extended Dysthe equations can be approximately integrated by selecting a nearby theta function formulation. I study the subclass of wave equations that are in the form of nonlinear envelope equations for which all members can be reduced to a particular Hirota bilinear form. To find the approximately integrable formulation associated with a nonintegrable equation, I first study the one and two soliton solutions and subsequently extend these to larger numbers of solitons to obtain the Hirota N-soliton solution (for infinite-plane boundary conditions). Subsequently, I address the one and two periodic solutions from the bilinear form, so that I can develop the associated Riemann theta function solution to a nearby integrable case. I discuss how to obtain the higher order breather packets from the point of view of the theta functions. This work is being developed for real time analysis of shipboard radar analysis of ocean waves. Further applications include real time analysis of lidar and synthetic aperture radar (SAR) data taken by airplanes flying over high sea states.
Numerical Simulations of KCS Parametric Rolling in Head Waves
Authors: Wang Shuang , Wei Junkai , Chen Xuanshu , Liu Liwei , Zhang Zhiguo 
Published: November 2019

Abstract
As a type of the ship stability failure modes, parametric rolling has attracted more attention from many researchers in recent years because of a series of accidents due to ship instability, especially the instability of container ship. Parametric rolling is a complex nonlinear stochastic dynamic problem, which is often accompanied by large amplitude vertical motions of ships. At present, there are many difficulties in the research of ship parameter rolling, mainly including the nonlinearity of parameter rolling motion, the random variation of wetted area of the hull surface up to the incident wave waterline and the coupling effect of rolling, pitching and heaving. Nowadays, the potential flow theory is a common method to predict parametric rolling, but this method may generate results with low accuracy in some conditions. This paper describes a numerical simulation method based on in-house CFD code HUST-Ship to analyze parametric rolling motion of KCS (KRISO Container Ship) container ship model. The paper studies the occurring conditions of parametric rolling motion of KCS model and reveals the mechanism of parametric rolling.
Analyzing the Effect of Shaft and End-Plates of a Newly Developed Elliptical-Bladed Savonius Rotor From Wind Tunnel Tests
Authors: Alom Nur , Kumar Nitish , Saha Ujjwal K. 
Published: November 2019

Abstract
In recent times, drag-based vertical-axis wind turbine rotors have gained increasing interests in offshore applications because of their performance potential and reliability. Their advantages like simplicity, easier manufacture and lower maintenance cost have attracted the researcher’s attention toward improving their design further. However, this type of rotor is still suffering from lower efficiency than the lift-based Darrius and the horizontal-axis wind turbine rotors. A recently developed elliptical-bladed Savonius rotor has shown its potential to harvest wind energy more efficiently. However, the geometric parameters of this rotor such as aspect ratio, overlap ratio, number of blades, shaft and end plates, the aerodynamic parameters such as Reynolds number, lift and drag coefficients are needed to be optimized for further improvement of its performance. In the present investigation, the wind tunnel tests have been conducted to analyze the effect of shaft and end-plates of a newly developed elliptical-bladed vertical-axis Savonius wind turbine rotor. Experiments have been conducted over a range of tip speed ratios to find the torque and power coefficients of a two-bladed rotor system for two individual cases viz., the rotor with a shaft and the rotor with end-plates. In order to have a direct comparison, the experimental data are also obtained for the same rotor without the shaft and without the end-plates. The wind tunnel tests have demonstrated an improvement of power coefficient by 26.31% for the rotor with the end plates.
A Fluid-Structure Interaction Study on a Passively Deformed Fish Fin
Authors: Luo Yang , Xiao Qing , Shi Guangyu , Yuan Zhiming , Wen Li 
Published: November 2019

Abstract
In this paper, the propulsive performance of a caudal peduncle-fin swimmer mimicking a bio-inspired robotic fish model is numerically studied using a fully coupled FSI solver. The model consists of a rigid peduncle and a flexible fin which pitches in a uniform flow. The flexible fin is modeled as a thin plate assigned with non-uniformly distributed stiffness. A finite volume method based in-house Navier-Stokes solver is used to solve the fluid equations while the fin deformation is resolved using a finite element code. The effect of the fin flexibility on the propulsive performance is investigated. The numerical results indicate that the compliance has a significant influence on the performance. Under the parameters studied in this paper, the medium flexible fin exhibits remarkable efficiency improvement as well as thrust augment, while the least flexible fin shows no obvious difference from the rigid one. However, for the most flexible fin, although the thrust production decreases sharply, the efficiency reaches the maximum value. It should be noted that by non-uniformly distributing the rigidity across the caudal fin, our model is able to replicate some fin deformation patterns observed in both the live fish and the experimental robotic fish.