bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Importance of the Coupling Between Transient Mechanical, Hydraulic and Thermal Effects for the Modelling of Real-Time Drilling Operations
Authors: Dvergsnes Erik Wolden , Cayeux Eric 
Published: November 2019

Abstract
Because of the increased importance for the drilling industry to deliver drilling automation solutions, model-based applications for the analysis and control of the drilling process, have become an attractive approach towards improved performance and increased safety. A critical characteristic for such applications is its ability to perform accurate simulations of the drilling operation in real-time, based on a detailed description of the wellbore.
In a real-time context, the boundary conditions of the drilling system are seldom constant, therefore reinforcing the importance of utilizing transient models of the drilling process instead of steady state ones. Typical domains that require modelling are related to the mechanical, hydraulic and heat transfer aspects of a drilling operation. The time constants of the force-, momentum-, mass- and energy-conservation equations are sufficiently different to allow for solving each of these equations with different time discretization schemes. Yet, side effects influence the results from each other’s and therefore a time coupling shall nevertheless be accounted for.
For instance, for a drilling operation conducted on a floater, the heave induced movement at the top of the string propagates along the drill-string, therefore causing a displacement that induces swab and surge pressure variations, which themselves generate counter-acting forces on the drill-string. In such conditions, both the mechanical and hydraulic frictions generate heat that changes the in situ thermal conditions and therefore the drilling fluid mass density and its rheological behavior. Consequently, heat exchange caused by the drill-string and fluid movements also influences the hydraulic response of the system. Furthermore, thermal expansion will also apply to the drill-string.
In this paper, we discuss recent advances related to the coupling between transient mechanical, hydraulic and thermal models, where a key criterion is that the combined drilling model shall be capable of running in real-time on a standard computer. Incorporating these transient models is considered a necessary step towards improved accuracy of simulations, especially on floaters, where heave effects become important. We illustrate various effects by presenting and discussing several simulations results in detail.
Numerical and Experimental Modelling of Wave Loads on Thin Porous Sheets
Authors: Mackay Ed , Johanning Lars , Ning Dezhi , Qiao Dongsheng 
Published: November 2019

Abstract
This work considers the numerical modelling of wave interaction with thin porous structures, based on tests conducted in simplified conditions. Wave flume tests were conducted to measure the wave loads on thin porous sheets extending over the full water column. The porous sheets tested had a range of porosities, hole separation distances and thicknesses. Numerical and analytic models for the wave forces on the porous sheet are formulated under the assumptions of either a linear or quadratic pressure loss across the porous sheet. An iterative boundary element method (BEM) model is formulated to solve the quadratic pressure loss across the porous sheet.
It is shown that the assumption of a linear pressure loss at the porous boundary is inadequate to capture the variation in the wave load with both wave frequency and amplitude, but that the quadratic model is in good agreement with the measured forces. The porosity of the sheet is shown to have the dominant effect on the wave loads. The hole separation distance affects the phase of the force on the porous wall, but has only a small effect on the amplitude of the force. The sheet thickness is shown to have a small effect on the amplitude of the force but a significant effect on the phase of the force.
The results are of interest for numerical modelling of structures with thin porous boundaries in a wide range of contexts such as breakwaters, aquaculture and offshore structures with porous elements designed to reduce loads.
On Digital Twin Condition Monitoring Approach for Drivetrains in Marine Applications
Authors: Johansen Sigrid S. , Nejad Amir R. 
Published: November 2019

Abstract
A digital twin is a virtual representation of a system containing all information available on site. This paper presents condition monitoring of drivetrains in marine power transmission systems through digital twin approach. A literature review regarding current operations concerning maintenance approaches in todays practices are covered. State-of-the-art fault detection in drivetrains is discussed, founded in condition monitoring, data-based schemes and model-based approaches, and the digital twin approach is introduced. It is debated that a model-based approach utilizing a digital twin could be recommended for fault detection of drivetrains. By employing a digital twin, fault detection would be extended to relatively highly diagnostic and predictive maintenance programme, and operation and maintenance costs could be reduced. A holistic model system approach is considered, and methodologies of digital twin design are covered. A physical-based model rather than a data based model is considered, however there are no clear answer whereas which type is beneficial. That case is mostly answered by the amount of data available. Designing the model introduces several pitfalls depending on the relevant system, and the advantages, disadvantages and appropriate applications are discussed. For a drivetrain it is found that multi-body simulation is advised for the creation of a digital twin model. A digital twin of a simple drivetrain test rig is made, and different modelling approaches were implemented to investigate levels of accuracy. Reference values were derived empirically by attaching sensors to the drivetrain during operation in the test rig. Modelling with a low fidelity model showed high accuracy, however it would lack several modules required for it to be called a digital twin. The higher fidelity model showed that finding the stiffness parameter proves challenging, due to high stiffness sensitivity as the experimental modelling demonstrates.
Two industries that could have significant benefits from implementing digital twins are discussed; the offshore wind industry and shipping. Both have valuable assets, with reliability sensitive systems and high costs of downtime and maintenance. Regarding the shipping industry an industrial case study is done. Area of extra focus is operations of Ro-Ro (roll on-roll off) vessels. The vessels in the case study are managed by Wilhelmsen Ship Management and a discussion of the implementation of digital twins in this sector is comprised in this article.
CO2-Foam Rheology Behavior Under Reservoir Conditions
Authors: Al-Qasim Abdulaziz S. , Kokal Sunil , AlOtaibi Fawaz 
Published: November 2019

Abstract
Super critical carbon dioxide (SC-CO2) flooding is one of the most important enhanced oil recovery (EOR) methods used for conformance control and deep diversion of SC-CO2. It minimizes gravity override of SC-CO2 bypassing oil in the lower part of the formation. This paper investigates the impact of various parameters such as liquid/liquid ratio, different foam qualities and different injection modes on the SC-CO2-foam quality and its rheological properties.
SC-CO2 foam can control the SC-CO2 mobility, enhance the sweep efficiency in reservoirs and improve the conformance control. Experimental results shows that combining foam with supercritical and dense CO2 will reduce the mobility of SC-CO2 to oil and water, stabilize the SC-CO2 injection front and mitigate the gravity override to a great extent resulting in less amount of unwept oil and better displacement efficiency and more recovery gain.
Different set of lab experiments designed and conducted to identify the right ratio that can drastically increase SC-CO2 viscosity. In this work, we explored the rheological properties of SC-CO2 foam/gel chemicals with different pressure and temperature. Two different types of surfactants were tested. The experimental setup and conditions were designed to allow surfactant to mix with SC-CO2 under high reservoir pressure and temperature (HPHT) to create foam to evaluate and screen the foam quality and texture.
The rheological properties of the SC-CO2-foam were investigated by varying the shear rate, shear stress, foam quality, injection modes and foaming agent concentrations at reservoir conditions. The effects of foam quality and liquid/liquid ratio, pressure and temperature on SC-CO2-foam at synthetic brine-environment rheology behavior, stability and mobility of foam were investigated. The foam study experiments were conducted using different scenarios: once by injecting SC-CO2 and surfactant solutions simultaneously and another time by alternate injection of CO2/surfactant solution at different flow rates at different foam qualities. The experimental results have shown that the foam mobility (total mobility of CO2 /surfactant solution) decreased with increasing foam quality ranging from 20% to 80%. The rheological properties of N2-foam were investigated and compared with SC-CO2-foam properties. This was correlated with the images of the high pressure, high temperature (HPHT) foams that were captured through microscope at different time intervals and analyzed to indicate their stability.
CFD Modelling to Investigate Design of a Whaleback-Type Forecastle for Greenwater Protection
Authors: Chen Lifen , Zhang Xiantao , Taylor Paul H. , Draper Scott , Wolgamot Hugh 
Published: November 2019

Abstract
In extreme weather permanently moored FPSOs may be overtopped by large amounts of greenwater, resulting in damage to deck structures and downtime. Thus, the preliminary design process for FPSOs has often included structural protection to mitigate loads from greenwater on deck and ensure structural integrity of top side structures at the bow in harsh sea conditions. This paper numerically investigates greenwater at the bow of an FPSO fitted with a ‘whaleback’ or ‘duck-bill’ shaped forecastle that is represented as an angled extension to the freeboard. In this study, the whaleback forecastle is intended to completely deflect the greenwater flow off the forecastle head. Previously validated numerical models based on OpenFOAM, an open source Computational Fluid Dynamics (CFD) package, are used. The (vertical) run-up height and the forces on the whaleback are analysed based on the CFD results to quantify the effectiveness of the design. It is found that the parameter tan β (FE/λp) that combines the coupled effect of the whaleback geometry and the incoming wave is important for determining the run-up height. The use of this parameter leads to a crude method for fast estimates of the effectiveness of such structures. Increase of the slope of the whaleback forecastle increases the run-up height, thus, increases the horizontal greenwater loading on such structure, however, the direct effect of the slope on the horizontal greenwater loading is found to be limited. An opposite trend is observed for the vertical greenwater loading in which the forecastle slope still plays a significant role even if the effect of run-up height is excluded, as a result of overtopping volume. Additionally, the vertical component of greenwater loading dominates the total greenwater loading on the whaleback forecastle.
Numerical Study of Breaking Waves and Associated Wave Forces on a Jacket Substructure for Offshore Wind Turbines
Authors: Aggarwal Ankit , Martin Tobias , Shirinov Seimur , Bihs Hans , Kamath Arun 
Published: November 2019

Abstract
The interest towards offshore wind energy has grown manifolds in the last few decades. Jacket structures are one of the most widely used substructures in the offshore wind turbine installations for intermediate water depths. Offshore structures are exposed to breaking waves. The interaction of breaking waves with the jackets is quite complicated due to the multiple vertical, horizontal and diagonal members. In the present study, a numerical investigation of the wave hydrodynamics and wave forces exerted by regular breaking waves on a jacket is performed. The open-source CFD code REEF3D is used for this purpose, which raises the possibility to model the breaking process physically. The conducted model-scale laboratory experiments have been performed in the past such that a direct comparison is presented.
Overview of the Lateral Buckling and Walking Designs of Deepwater Pipelines in Offshore Brazil
Authors: Solano Rafael F. , Cardoso Carlos O. , Antunes Bruno R. 
Published: November 2019

Abstract
Last two decades have been marked by a significant evolution on the design of HP/HT subsea pipelines around the world. The HotPipe and SAFEBUCK JIPs can be seen as the first deepened developments in order to obtain safe design guidelines for subsea pipelines systems subjected to global buckling and walking behaviors. The adopted design approach have been to allow exposed pipeline buckles globally on seabed in a safe and controlled manner. Otherwise, the walking phenomenon has been in general mitigated constraining axial displacements by means of anchoring systems.
After several design and installation challenges concerning lateral buckling and pipeline walking behaviors, nowadays there is a significant amount of deepwater pipelines operating with buckle initiators (triggers) as well as walking mitigation devices in offshore Brazil. Oil and gas pipelines, short gathering lines and long export lines, installed by reeling and J-lay methods, in other words different kinds of subsea pipelines have operated on very soft clayey soils and have formed planned lateral buckles as well as rogue buckles.
This paper presents the main characteristics and design challenges of the deepwater pipelines subjected to the lateral buckling behavior, also highlighting mitigation measures to constrain the walking phenomenon of some pipelines. The relevant design results are highlighted as type and number of buckle triggers, buckle spacing, type and locations of walking mitigations. Envelopment of the main design parameters are mapped in order to identify some trends. Finally, survey images of operating pipelines are presented confirming behaviors predicted in the design phase.
Air-Gap Analysis of a Semi-Submersible Considering Full Second Order Effects
Authors: Pan Zhiyuan , Vada Torgeir Kirkhorn , Nestegård Arne 
Published: November 2019

Abstract
In the present paper, a complete and consistent second-order computation of airgap for a semi-submersible is presented. The second-order sum and difference frequency upwell will be calculated and combined with the linear upwell statistically to find the short-term extremes. The phasing of the low frequency surface elevation with respect to the low frequency vertical motion will be considered. The asymmetric characteristics of the surface elevation will be taken care of by the sum frequency surface elevation. By comparing the maximum and minimum extremes of surface elevation in a given sea state at specified off-body points, the “asymmetry factor” up to the second order can be obtained.
Effects of Euler Angles of Vertical Cambered Otter Board on Hydrodynamics Based on Response Surface Methodology and MOGA
Authors: Wang Gang , Wan Rong , Huang Liuyi , Zhao Fenfang , Wang Xinxin , Zhu Wenbin , Wang Lei , Xu Qingchang , Li Yuyan 
Published: November 2019

Abstract
In this present work, effects of three Euler angles (Angle of Attack (AOA), Angle of Trim (AOT), Angle of Pitch (AOP)) of vertical cambered otter board on hydrodynamic characteristics (drag coefficient (Cd), lift coefficient (Cl), center-of-pressure coefficients (Cp)) were studied based on numerical simulation combined with Kriging Response Surface Methodology (KRSM) and Multi-Objective Genetic Algorithm (MOGA). Wind tunnel experiments were carried out to validate the accuracy of response surface based on numerical simulation. It was demonstrated that AOA had prominent effects on Cd and Cl, while AOT and AOP had less effects. The working posture of otter board were recommended to lean inwards (0°∼6°) and forward (−10°∼0°) to improve the lift-drag ratio without sacrificing Cl. The influences of AOT and AOP on positions of center-of-pressure point were less significant than that of AOA and decreasing with the increase of AOA. In addition, response surface of hydrodynamic coefficients around the critical AOA was a decent indicator of occurrence of stall. Finally, three candidate cases were selected to satisfy the high working efficiency by MOGA, which was consistent with the above recommendations. This study provided a scientific reference of response surface experimental investigations methodology and the configuration of Euler angles of otter board.
On Calculating the Crack Growth Within a Single Load-Dwell-Unload Cycle for Metal Structures
Authors: Wang Fang , Zhang Xuezhong , Jiang Zhe , Cui Weicheng 
Published: November 2019

Abstract
Some structures such as components of deep-sea submersibles, will endure cyclic loads with a period of dwell time at high stress level within each loading-unloading cycle. For components subjected to cyclic loads, fatigue life analysis is an important issue. Approaches based on fracture mechanics are reliable, in which choice of crack growth model plays an important role. The commonly-used crack growth rate model can make fatigue crack increment by cycle-by-cycle integration, which neglects the crack length change within a single cycle. Some researchers proposed the concept of crack growth rate model in small time domain to consider the crack growth within one load-unload cycle. However, during the dwell time, the crack increment can also be detected. In this paper, the model in small time domain will be extended to that for a single load-dwell-unload cycle. The model can be applied to calculate the life of metal structures under dwell-fatigue conditions.
Development of a PID Control Strategy for a Compact Autonomous Underwater Vehicle
Authors: Sahoo Avilash , Dwivedy Santosha K. , Robi P. S. 
Published: November 2019

Abstract
This paper presents a proportional-integral-derivative (PID) control strategy for navigation of a compact autonomous underwater vehicle (AUV) developed in-house. The AUV has a closed frame, neutrally buoyant, three-part modular structure made up of glass fibre composite material. Three fix position bi-directional thrusters are used for propulsion. A detailed CAD model of the AUV is developed using the modelling software SOLIDWORKS to estimate different system parameters. Hydrodynamic parameters are estimated from the ANSYS Fluent simulations of the AUV structure. Using the system parameters, a six degrees of freedom (DOF) dynamic model is developed, which is further simplified to a 4 DOF model. A 3D guidance system is developed for path planning using Line-of-Sight (LOS) strategy with way-point navigation. A closed loop PID controller is developed to follow the trajectory developed by the guidance system. The controller is simulated using MATLAB Simulink and the results are discussed.
At-Sea Experiment on Durability and Residual Strength of Polyester Rope for Mooring of Floating Wind Turbine
Authors: Utsunomiya Tomoaki , Sato Iku , Tanaka Koji 
Published: November 2019

Abstract
When using synthetic fiber rope as a mooring line of a floating body such as floating offshore wind turbine (FOWT), it is necessary to carry out characteristic test and to grasp well about strength, stiffness, durability against monotonic and cyclic loadings. In this research, we have made characteristics test of polyester rope based on ISO. Next, based on the obtained characteristic values (mass, stiffness, strength, etc.), the dynamic response analysis of the floating body-mooring system was carried out and the mooring design was carried out. It was actually operated as a floating body mooring line for about 1 year. During the operation period, no abnormality was found, nor appearance damage occurred. After completion of operation for 1 year, the polyester rope was collected and residual strength test was carried out. As a result, no serious deterioration situation such as infiltration of marine organisms or fracture of the strands due to wear between fibers was observed at all. On the other hand, with respect to durability, it was found that the strength reduction was 2.9% from the initial state with respect to the breaking strength.
Study on Mechanical Behavior of Tensile Armor Wires of Marine Flexible Pipes and Cables During Winding Process
Authors: Lu Qingzhen , Wu Shanghua , Wang Dong , Yang Zhixun , Yin Yuanchao , Hu Haitao , Yan Jun , Yue Qianjin 
Published: November 2019

Abstract
In this paper, a mechanical model of armor wire winding process is established to quantify the relationship between the tension force and the internal force of armor wire cross section in winding process. Then based on this model, a method for predicting the residual stress of armor wire cross section after winding is presented. The reasonable winding tension force and the minimum residual stress are discussed. In addition, the reasonable design of the processing equipment is further discussed. This paper provides a useful reference for the evaluation of key parameters and the prediction of residual stress in the processing of tensile armor layer of offshore flexible pipes and cables.
Validation of Numerical Models of the Offshore Wind Turbine From the Alpha Ventus Wind Farm Against Full-Scale Measurements Within OC5 Phase III
Authors: Popko Wojciech , Robertson Amy , Jonkman Jason , Wendt Fabian , Thomas Philipp , Müller Kolja , Kretschmer Matthias , Ruud Hagen Torbjørn , Galinos Christos , Le Dreff Jean-Baptiste , Gilbert Philippe , Auriac Bertrand , Oh Sho , Qvist Jacob , Sørum Stian Høegh , Suja-Thauvin Loup , Shin Hyunkyoung , Molins Climent , Trubat Pau , Bonnet Paul , Bergua Roger , Wang Kai , Fu Pengcheng , Cai Jifeng , Cai Zhisong , Alexandre Armando , Harries Robert 
Published: November 2019

Abstract
The main objective of the Offshore Code Comparison Collaboration Continuation, with Correlation (OC5) project is validation of aero-hydro-servo-elastic simulation tools for offshore wind turbines (OWTs) through comparison of simulated results to the response data of physical systems. Phase III of the OC5 project validates OWT models against the measurements recorded on a Senvion 5M wind turbine supported by the OWEC Quattropod from the alpha ventus offshore wind farm. The following operating conditions of the wind turbine were chosen for the validation: (1) Idling below the cut-in wind speed; (2) Rotor-nacelle assembly (RNA) rotation maneuver below the cut-in wind speed; (3) Power production below and above the rated wind speed; and (4) Shutdown. A number of validation load cases were defined based on these operating conditions. The following measurements were used for validation: (1) Strains and accelerations recorded on the support structure; (2) Pitch, yaw, and azimuth angles, generator speed, and electrical power recorded from the RNA. Strains were not directly available from the majority of the OWT simulation tools. Therefore, strains were calculated based on out-of-plane bending moments, axial forces, and cross-sectional properties of the structural members. Also, a number of issues arose during the validation: (1) The need for a thorough quality check of sensor measurements; (2) The sensitivity of the turbine loads to the controller and airfoil properties, which were only approximated in the modeling approach; (3) The importance of estimating and applying an appropriate damping value for the structure; and (4) The importance of wind characteristics beyond turbulence on the loads. The simulation results and measurements were compared in terms of time series, discrete Fourier transforms, power spectral densities, probability density functions of strains and accelerometers. A good match was achieved between the measurements and models set up by OC5 Phase III participants.