bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hybrid Method for Predicting Ship Manoeuvrability in Regular Waves
Authors: Mei Tianlong , Liu Yi , Tello Ruiz Manasés , Vantorre Marc , Lataire Evert , Chen Changyuan , Zou Zaojian 
Published: November 2019

Abstract
The ship’s manoeuvring behaviour in waves is significantly different from that in calm water. In this context, the present work uses a hybrid method combining potential flow theory and Computational Fluid Dynamics (CFD) techniques for the prediction of ship manoeuvrability in regular waves. The mean wave-induced drift forces are calculated by adopting a time domain 3D higher-order Rankine panel method, which includes the effect of the lateral speed and forward speed. The hull-related hydrodynamic derivatives are determined based on a RANS solver using the double body flow model. The two-time scale method is applied to integrate the improved seakeeping model in a 3-DOF modular type Manoeuvring Modelling Group (MMG model) to investigate the ship’s manoeuvrability in regular waves.
Numerical simulations are carried out to predict the turning circle in regular waves for the S175 container carrier. The turning circle’s main characteristics as well as the wave-induced motions are evaluated. A good agreement is obtained by comparing the numerical results with experimental data obtained from existing literature. This demonstrates that combining potential flow theory with CFD techniques can be used efficiently for predicting the manoeuvring behaviour in waves. This is even more true when the manoeuvring derivatives cannot be obtained from model tests when there is lack of such experimental data.
Added Resistance CFD Analysis of the KVLCC2 With the Naval Hydro Pack
Authors: Vukčević V. , Gatin I. , Kim G.-H. , Jasak H. 
Published: November 2019

Abstract
A CFD analysis of added resistance of a KVLCC2 ship model is presented in this paper. The Naval Hydro Pack, an open source software library for computational naval hydrodynamics based on OpenFOAM is used to perform the simulations.
Ten head wave cases are considered in this study ranging from short waves to long waves (wave length to length between perpendiculars ranging from 0.3 to 2). During the initial stages of our research, we had noticed significant over-prediction of added resistance compared to experimental results. After thorough analysis, the issue was found to be related to inadequate turbulence modeling using the standard k-ω SST model. Using the free surface sensitised model, the prediction of the added resistance improves significantly Compared to the experimental results, majority of the cases with different wave lengths have errors smaller than several percent. In addition to added resistance, heave and pitch motion amplitudes are compared to recent experimental results by Park et al. [1], showing good agreement. CPU time required to perform the computations is also discussed.
Development of an Image Processing Module for Autonomous Underwater Vehicles Through Integration of Object Recognition With Stereoscopic Image Reconstruction
Authors: Lin Yu-Hsien , Chen Shao-Yu 
Published: November 2019

Abstract
This study investigated the development of visual recognition and stereoscopic imaging technology, applying them to the construction of an image processing system for Autonomous Underwater Vehicles (AUVs). For the proposed visual recognition technology, an optical flow algorithm was used to detect the linear features and movement speeds of dynamic images; the proposed stereoscopic imaging technique employed a Harris corner detector to estimate the distance of the target. A physical AUV was constructed with a wide-angle lens camera and a binocular vision device mounted on the bow to provide image input. Subsequently, a simulation environment was established in Simscape Multibody and used to control the post-driver system of the stern, which contained horizontal and vertical rudder planes as well as the propeller. Finally, the dynamic testing results were combined with a fuzzy controller to output the real-time responses of the vehicle regarding the angles, rates of the rudder planes, and the propeller revolution speeds at various distances.
Estimating Operational Weather Downtime: A Comparison of Analytical Methods
Authors: Lambkin David , Wade Ian , Stephens Robin 
Published: November 2019

Abstract
Weather downtime (WDT) is a logistical and financial risk when planning operations or offering services. Such risk is typically identified and managed in advance using statistical predictions based on historical weather data. Estimates of programme and cost for offshore construction work may vary, not because of the nature of a task, or the environment at the location, or the capability and price of a vessel, but because estimates of WDT have been calculated in different ways.
Estimates of WDT are required in order to develop a realistic programme for complex and long duration projects. Therefore, a good understanding of the analytical options and a feel for the implications of the many and varied approaches is key to finding optimal solutions regarding WDT assessments.
In this paper we consider a number of variants to the two principal approaches (namely ‘Weather Windows’ and ‘Simulation Based’ WDT analysis) to the derivation of WDT statistics. WDT estimates calculated using the same environmental input data, but alternative approaches are presented. The presentation highlights the potential variation in downtime statistics that can result from the alternative analyses, aiming to improve awareness of the application of such statistics when estimating project programme and cost at the planning stages.
Method Evaluating Axial Response of Vertically-Loaded Piles During Spudcan Penetration
Authors: Fan Yifei , Wang Jianhua 
Published: November 2019

Abstract
Large soil deformation can be induced during spudcan penetration into stratum near an existing piled foundation of a fixed offshore platform, and some research has been done on the effects of spudcan penetration on the lateral response of an adjacent pile. However, available centrifuge model tests found that the maximum vertical soil displacements are manifested in the same magnitude compared with those in the lateral direction, leading to large negative friction along the pile shaft. Also, the combined loading effects of transmitted loads from the upper structure should be taken into account in axial analysis during spudcan penetration, which has been proved important in prediction of axial pile response due to soil movement. This paper investigates a method to quantitatively evaluate the effect of spudcan penetration on vertical response of an adjacent pile. The vertical soil displacement is found by first simulating a free field spudcan penetration by Coupled Eulerian-Lagrange (CEL) method. The flow field is then analyzed to calculate the displacement components at specific pile location. Then the predicted vertical soil displacement profile is input into the nonlinear foundation pile model to determine the axial response of an adjacent pile subjected to spudcan penetration-induced axial and pile head loads. The proposed method is adopted to analyze centrifuge model tests in sand and clay, and predicted results prove to be basically in agreement with measured ones.
Evaluation of Impact Loads on Offshore Jacket Platform During Float-Over Mating Operation
Authors: Kagita Gurumurthy , Addala Mahesh B. , Achary Gudimella G. S. , Sripada Subramanyam V. R. 
Published: November 2019

Abstract
In the mating phase of float-over operation, the topsides deck load from the vessel is transferred onto the jacket either by ballasting the vessel or by the combination of ballasting and hydraulic jacking system. During this phase of operation, the topsides and jacket experience impact loads through the contact points in a short duration of time. To evaluate the impact loads and to capture the transient effects precisely, a non-linear time domain hydrodynamic analysis is required. To obtain the design loads, generally the numerical jacking simulation is initiated at the time instant of maximum wave height when the jacking system is used. However, the conservative response may also depend on the relative velocity between the jacket and topsides legs. In this paper, a series of non-linear time domain as well as linear frequency domain hydrodynamic analyses are performed to evaluate the impact loads between 9000 tonne integrated topsides deck and a 4-legged jacket in a water depth of 50 m during float-over mating operation. The simulations are performed using MOSES software. The float-over hardware such as LMUs (leg mating unit), DSUs (deck support unit), Jacks, Fenders and Mooring lines are modelled as appropriate linear / nonlinear springs. The principle of the mating operation is considered through a combination of vessel ballasting and jacking operation. This paper discusses about random wave seed selection, effect of vessel response and wave headings on the impact loads of LMUs and Jacks/DSUs.
Sensitivity Analysis of Different Parameters of Taut Mooring System of a Truss Spar
Authors: Kang Zhuang , Chang Rui , Kang Youwei , Liu Shanchuan 
Published: November 2019

Abstract
The taut mooring system is widely used for some advantages, such as smaller mooring radius, lighter total weight and better anti-corrosion performance. In this paper, the taut mooring system of a Truss Spar platform which was taken as the research object was investigated under the condition of 2000 m water depth in South China Sea. Firstly, the main body of the platform was analyzed in frequency domain based on the 3-d potential theory, and then the nonlinear solutions of platform displacement and mooring line force were obtained by using coupling analysis method in time domain, which determined the preliminary design parameters of mooring system. The sensitivity of the taut system is studied by changing several design parameters such as the top angle of mooring line, cable hole position and method of mooring disposal. In summary, the variation of the motion and dynamic response of the platform and mooring system has been explored and summarized by studying the design process and influential parameter of dynamic characteristics of mooring system and optimizing ideas of relevant parameters, which can further provide technical support and engineering reference for the design and application of the taut mooring system of deepwater Truss Spar platforms.
Impacts of Reliability on Operational Performance and Cost of Energy Evaluation of Multi-Megawatt, Far-Offshore Wind Turbines
Authors: Dao Cuong D. , Kazemtabrizi Behzad , Crabtree Christopher J. 
Published: November 2019

Abstract
Wind energy is growing at a fast pace around the world. According to a report published by WindEurope, 55% of total power capacity installations in the EU came from wind in 2017. In this context, offshore wind plays a decisive role, with countries such as the UK leading the development of large-scale offshore wind projects within Europe and around the world. It is essential that the cost of energy from offshore wind remains competitive with other sources of energy to encourage further investment in offshore wind developments. One way to maintain and further reduce the cost of offshore wind energy is to take advantage of economies of scale by increasing the megawatt ratings of offshore wind turbines. On the other hand, the operational expenditure of the turbines could also be reduced significantly. In this paper, we present a new integrated operation simulation framework for performance evaluation of multi-megawatt direct drive wind turbines suitable for use in far offshore wind farms. The operation simulation considers several essential wind turbine data such as component reliability, i.e. failure rates and downtimes per failure, historical wind speed, turbine information, and repair cost per failure to estimate the operational and economic performance of the wind turbine in its entire lifetime. In the proposed operation simulation, component reliability models and a wind power model are coupled together to simulate wind turbine operation over its entire lifetime using a time-sequential Monte Carlo simulation. Since the reliability data for large-scale offshore wind turbines are scarce and/or restricted to only direct stakeholders, a range of operational profiles for the turbines based on different level of reliability are simulated. In addition, the economic performance of the turbine is measured by defining an index for levelised cost of energy as a function of component reliability. In this way, the wind turbine reliability, power output, failure cost and levelised cost of energy are estimated under the variation of input reliability data. The results of this paper can inform wind turbine performance depending on the reliability of its components, and provide useful information for critical components identification and economic assessment of future far offshore wind turbines.
Hydrodynamic Forces on Intermittently Spanning Pipelines in Steady Currents
Authors: Teng Yunfei , Cheng Liang , An Hongwei , Tong Feifei , Griffiths Terry , Sun Wei , Chi Jiawei , Xiong Zhijian 
Published: November 2019

Abstract
Experimental investigations on the hydrodynamic forces on an intermittently spanning pipeline exposed to steady currents were carried out. The effect of intermittent local spanning sections on the global hydrodynamic behavior was studied by changing the ratio between the non-spanning length (B) and the total length (L), namely the blocking ratio B / L. A range of gap height (G) to diameter (D) ratios, i.e. gap ratio G / D, and 4 different Reynolds numbers (Re) in the subcritical region were tested in the experiments. The results show: i) for a certain gap ratio, the mean drag increases gently with the decreasing blocking ratio at Re = 5.5 × 104, whereas the mean lift decreases significantly with the decreasing blocking ratio at all values of Re tested; and ii) for a certain blocking ratio, increasing the gap ratio leads to an increase in mean drag and decrease in mean lift. Further, simple approaches are proposed based on the present dataset for estimating the global effects on hydrodynamic drag and lift forces due to local spanning geometry.
Hydrodynamics Interactions on Vortex-Induced Motions of a Multi-Body Floating System
Authors: Liang Yibo , Tao Longbin 
Published: November 2019

Abstract
In this study, numerical analysis has been carried out to investigate the hydrodynamic interactions of two multi-columns platforms. The objective of the work is to preliminarily evaluate the feasibility of a tension-leg-platform (TLP) dry tree unit (DTU) with tender assisted drilling (TAD) from the aspect of vortex-induced motions, characterized by the current. Two multi-columns floating platforms with a small gap ratio (28% of the overall platform width) are numerically simulated with the scenario of 3 degree-of-freedom (DOF) on the horizontal plane (including transverse, in-line and yaw motions). A comprehensive numerical simulation was conducted to examine the hydrodynamics interactions due to the flow over two floating platforms. Horizontal plane motions including transverse, in-line and yaw motions as well as drag and lift forces on both structures are discussed. The numerical data on the multi-body VIM interactions within the “lock-in” region will serve as a preliminary study for future coupled motions analysis of the TLP-TAD system design.
Fatigue Tests on Corroded Mooring Chains Retrieved From Various Fields in Offshore West Africa and the North Sea
Authors: Ma Kai-tung , Gabrielsen Øystein , Li Zhen , Baker David , Yao Aifeng , Vargas Pedro , Luo Meng , Izadparast Amir , Arredondo Alberto , Zhu Linfang , Sverdlova Nina , Skutle Høgsæt Ingrid 
Published: November 2019

Abstract
When an aged mooring system seeks a life extension, it is necessary to assess the remaining fatigue life of the corroded mooring chain. This paper summarizes the results of fatigue tests performed on mooring chain samples retrieved from six different fields in West Africa and North Sea. The impacts of corrosion on fatigue life on the samples were researched. The tests were managed under a Joint Development Project, “Fatigue of Corroded Chains (FoCCs JDP)”. The objectives of the JDP are (1) to derive a methodology for assessing the remaining fatigue life of corroded chain, (2) to develop guidance for performing reliable FEA of chain links to assess remaining fatigue life, and (3) to provide more rational basis to improve industry guidance on mooring line replacement criteria for life extension. Fatigue test procedure was defined by the fifteen (15) participating members. The procedure specified the testing parameters, including mean tension, tension range, and test frequency. Six sets of fatigue tests have been completed in seawater with the number of cycles to failure recorded. These chain samples were retrieved from floating production and storage units, e.g. FPSOs and FSUs, that were still in service. Fatigue data obtained from the tests were plotted against the design SN curves and results from fatigue testing of new chain. It was found that most of these samples have limited amount of fatigue capacity remained. Most interesting finding is that the sharpness of the surface feature on the corroded chain link has a significant impact on the remaining fatigue life. Another interesting finding is that the surface feature created by corrosion can be quite distinct and unique depending on the geophysical locations where the sample came from. These findings and test results may serve as references for life extension assessment of an aged mooring system.
Staggered Grooves for the Suppression of Vortex-Induced Vibration in Flexible Cylinders
Authors: Law Yun Zhi , Jaiman Rajeev K. 
Published: November 2019

Abstract
Vortex-Induced Vibration (VIV) remains a challenge to the offshore structures such as deepwater riser and subsea pipelines, which require a robust and cost-effective control to circumvent the impact of the dynamic loads and the fatigue damage. While the state-of-the-art helical strakes are effective in the suppression of VIV amplitudes, they cause a higher drag force and bending moment on the submerged structure. In this work, we numerically investigate the recently proposed staggered groove concept to reduce both the VIV amplitudes and the drag force. The staggered groove is constructed by aligning the square grooves alternatively along the spanwise (axial) direction of the cylinder. The performance of the staggered groove concept is examined in three dimensions for two VIV configurations at subcritical Reynolds number (Re) namely: (i) two-degree-of-freedom elastically mounted rigid cylinder (Re = 3000–10000), and (ii) pinned-pinned flexible cylinder in a uniform current flow at Re = 4800. Their characteristic responses and the vortex dynamics are compared to their plain cylinder counterparts. For the two VIV configurations, our results show a remarkable reduction of both the peak vibration amplitude and the drag force up to 40% and 20%, respectively. Further analysis has shown that such reduction is related to the diminishing of the spanwise correlation of hydrodynamic forces due to the alternating alignment of the grooves. Such effect on the spanwise correlation leads to the broadening of the frequency spectra of the forces, thereby reduces the average power transferred to the cylinder and leads to the VIV suppression.
Effect of Buoyancy and Inertia on Viscoplastic Fluid-Fluid Displacement in an Eccentric Annulus With an Irregular Section: Part 2 — Displacements in Vertical Annulus
Authors: Skadsem Hans Joakim , Kragset Steinar 
Published: November 2019

Abstract
Casing strings and liners are important subsurface structural components in petroleum and in geothermal wells. After the casing string has been run in hole, it is cemented to the formation by pumping a sequence of spacer fluids and cement slurry into the annulus outside the string. Spacer fluids are usually pumped ahead of the cement slurry in order to displace the drilling fluid from the annulus that is to be cemented, and thereby avoid contamination of the cement slurry. Fluid displacements are governed by inertia, buoyancy and viscosity effects, in addition to being strongly influenced by the annular geometry. Poor centralization of the casing or irregularities such as washouts can influence the displacement flows both locally and over long axial distances.
We present three dimensional numerical simulations of the displacement flow involving two viscoplastic fluids in the vicinity of a symmetric local hole enlargement. We focus on laminar flow regimes in the regular part of the annulus and investigate how the volumetric flow rate and the mass density difference between the fluids affect the displacement efficiency in the regular and the irregular parts of the annulus. This study considers viscoplastic displacement flows in a near-vertical, irregular annulus and is an extension of a previous publication that focused on a near-horizontal annulus.
We contextualize our simulations by comparison to industry guidelines for effective and steady laminar displacements in the regular, near-vertical annulus. Here, eccentricity favors flow in the wider sector of the annulus while a positive density difference between the fluids generates secondary, azimuthal flow toward the narrow side of the annulus. In the enlarged and irregular section, both the axial bulk velocity and casing eccentricity decrease sharply and buoyancy becomes more pronounced compared to in the regular annulus. We quantify and discuss the effects of local hole enlargements on displacement efficiencies. Simulations of cementing flows can aid in optimizing fluid properties and pump rates, including when the wellbore has suspected or confirmed zones of irregular geometries.
Wind and Current Loads on Barges and Ships
Authors: el Moctar Ould , Schellin Thomas E. , Neugebauer Jens 
Published: November 2019

Abstract
Increased waterborne trade has led to the construction of ever larger ships and barges as oversized modules are transported by sea. The provision of tugs for towing such vessels has become a serious issue, especially in restricted areas often characterized by coastal regions of limited water depth. Wind loads are most relevant for towing operations because large forces act on the sail area and submerged hull of the towed vessels, such as construction barges when carrying oversized modules or fully laden containerships. Systematic steady and unsteady numerical simulations were performed using a RANS-based field method to predict wind and current forces and moments acting on representative construction barges, containerships, tankers, and passenger ships. Aero- and hydrodynamic computations were carried out separately. Aerodynamic computations considered various deck load configurations to represent realistic loading conditions; hydrodynamic computations accounted for finite water depth. Agreement with available wind tunnel experimental data was generally favorable.
Our purpose was to provide a reference for wind and current loads on different barge and ship types. The objective was not to investigate flow details needed for, e.g., smoke propagation, helicopter landing, etc. This has been covered by other researchers.