bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Modelling of Wave Interaction With an FPSO Under Different Incident Wave Conditions
Authors: Kamath Arun , Martin Tobias , Bihs Hans 
Published: November 2019

Abstract
Numerical modelling of wave interaction with offshore structures provides deep insights into the complex wave hydrodynamics and the wave-structure interaction problem. Offshore structures such as an FPSO vessel are susceptible to continuous wave loading under operational conditions and catastrophically large wave loadings under extreme conditions. It is essential to obtain accurate information on the environmental forcing due to waves on an FPSO to reliably predict the operational conditions to optimise the operational times while considering operational safety. In addition, the wave hydrodynamics involved under extreme wave conditions also have to be evaluated in order to predict the survivability of the vessel and avoid major accidents at sea.
In the current study, the open-source hydrodynamic model REEF3D is used to study the wave interaction with an FPSO structure. The numerical results are compared to available experimental data for the free surface around the structure, the pressure due to wave incidence and the motion of the structure. The wave interaction with the structure is studied for a fixed structure and considering the six degrees-of-freedom for a floating object. Different incident waves are simulated including irregular waves using the JONSWAP spectrum and phase-focussed irregular waves. The model solves the incompressible Reynolds-averaged Navier-Stokes equations with high-order discretization schemes for convection and time discretization. The local directional immersed boundary ghost cell method extended to three dimensions is used to represent the boundaries of complex objects. The level set method is used to obtain a sharp free surface. The Poisson pressure equation is solved using the multi-grid preconditioned BiCGStab algorithm provided by the Hypre high performance solver library. The numerical model is fully parallelised using the MPI library.
Experimental Study on the Hydrodynamic Characteristics of Artificial Reefs
Authors: Zhao FenFang , Ong Muk Chen , Tang Yanli , Wang Xinmeng 
Published: November 2019

Abstract
Artificial reefs (ARs) are structures constructed on the seabed to attract and concentrate fish and to potentially improve and rehabilitate coastal ecosystems. In order to investigate the hydrodynamic characteristics of ARs, a series of model experiments of cubic artificial reefs are carried out in the flume. The model reefs are made of acrylic material with different shapes of opening and various open-area ratios. The hydrodynamic forces of the models are measured in the experiments. The changes of drag coefficient with respect to the open-area ratio and the flow-facing angle of attack are investigated and discussed respectively.
Virtual Prototyping and Simulation of Multibody Marine Operations Using Web-Based Technologies
Authors: Fonseca Ícaro A. , de Oliveira Felipe F. , Gaspar Henrique M. 
Published: November 2019

Abstract
This paper focuses on virtual prototyping and simulation of marine operations based on web technologies. The ship is represented as a digital object, which can be used to perform different types of analyses and simulations. The presented simulations are: motion of a single hull and of multiple hulls in regular waves calculated with closed-form expressions, induced pendulum motion response to a lifted load, and motion of a barge with initial movements in still water calculated with equations of motion.
The simulations are developed as web applications in JavaScript and HTML, with graphical user interfaces and 3D renders of the operations. Relevant parameters of the simulations such as wave characteristics and design dimensions are linked to interactive dashboards, allowing the user to modify them and visualize the results in real-time. The applications are lightweight enough to be executed locally in the web browser of most modern devices.
The work employs an open source approach, relying most notably on the Vessel.js library. This aims to foster reuse of models and collaboration with external contributors.
Three-Dimensional Dynamic Analysis Method of Multi-Component Mooring Lines
Authors: Hermawan Yuda Apri , Furukawa Yoshitaka 
Published: November 2019

Abstract
Complicated mooring system well-known as a multi-component mooring line is highly required owing to the deep depth of water and severe sea conditions. Since the dynamic behaviors of such mooring line are quite complex, proper numerical method is indispensable to predict the dynamic behaviors of a multi-component mooring line efficiently and precisely. In this paper, a numerical method improving the lumped mass method is proposed to introduce the three-dimensional dynamic analysis of multi-component mooring line with the motion of an anchor and clump weights. The mooring line is regarded as a multi-component object which has nonuniform segment line characteristics. In this method, lumped mass technique is developed to represent the three-dimensional dynamic behavior of each segment individually, allowing the motion of bottom-end segment as well as the anchor. Then, the motion of the end-segment is regarded as the motion of the upper-end of lower segment. Meanwhile, calculation method of initial condition for dynamic calculation is developed by adopting the basic principle of multi-component mooring line catenary equations. The results of time histories representing the three-dimensional dynamic analysis of mooring line are obtained and compared with other numerical and experimental results presented in published papers. The results show good agreement with both numerical and experimental results.
A Method for Designing the Backbone for the Segmented Model of an Ultra-Large Container Carrier
Authors: Li Hui , Zou Jian , Sheng Weijia , Hu Xuecong , Hu Wenjia 
Published: November 2019

Abstract
The segmented model test is often used to study the wave load characteristics of large ships as it can account for the hydroealstic effect. The vertical bending moment (VBM) is of crucial importance in ensuring the safety of ocean-going vessels in rough seas, and there exists in the literature a large number of experimental studies of the VBM. For ships with large openings in the deck, for instance, container ships, the lateral wave loads, such as horizontal bending moment (HBM) and torsional moment (TM) in quartering seas, are as important as VBM. There are, however, few studies on the measurement of the coupled horizontal-torsional vibrations of such ships in model tests. In the paper, a method is proposed for designing flexible backbone models that satisfy the similarities of vertical and horizontal bending stiffness as well as the torsional stiffness, and the measurement of the wave load components is also described. In order to meet the similarity of the hull girder stiffness, the backbone cross-section of a complex form is designed. Finite element method (FEM) is used to calculate the natural frequencies and mode shapes of the segmented model. Measurement of the vertical bending moment, horizontal bending moment and torsional moment are calibrated by applying various combinations of loads.
The Use of Ensemble Forecast in Defining Offshore Installation Operability: A Case Study on Umbilical Shore Float-In Operations
Authors: Tinoco Francisco , Ting Kee Chien , Chavan Kishor 
Published: November 2019

Abstract
To address the uncertainty in both the monitoring and the forecasting of the environmental conditions for offshore operations, DNV recommends the use of Alpha factors. These factors are defined for the environmental conditions in North Sea and the Norwegian Seas. Since no localised Alpha factors are available for regions outside of North Sea, these factors are conservatively applied everywhere in the world. In a region with benign weather characteristics such as the Mediterranean, this could be overly conservative for the selection of operational weather windows. A deterministic weather forecast is sufficient to assess weather risk for short term operations; nonetheless, uncertainties of longer term predicted weather should still need to be addressed.
Shore float-in of umbilicals and cables requires a number of sequential activities with associated durations that build up to a total timeframe. This timeframe is beyond what can be accurately assessed using only deterministic weather forecasts. The operational activities are also very sensitive to tidal, current & sea-state variation; particularly associated with the use of personnel in the water like divers and waders for the removal of floats and the use of small crafts for control of the of the product alignment.
The use of Ensemble Forecast which utilises probabilistic approach compared to the deterministic approach, addresses the uncertainty of long term weather forecasting and remove artificially added conservatism such as the Alpha factor. This forecast is derived from multiple simulations, each with minor variations of initial conditions and slightly modified weather models.
Ensemble Forecast has been applied in offshore operation planning and execution in a project offshore Egypt in Mediterranean; particularly for a shore float-in of a main umbilical. It was used to define the main operational window, the start of the operation and weather risk beyond deterministic weather forecast.
The use of the Ensemble Forecast for selection of overall weather window has been shown to optimise operability, reduce the risk of product being damaged, provide added confidence in the offshore operational safety for the personnel involved while minimising waiting on weather.
The strategy of defining storm riding configuration for umbilical could enhanced overall operability. When the operational restrictions relating to limiting activities are anticipated to be surpassed but remains still within the storm riding sea-state, these activities could be safely halted and product held in place in stand-by mode until the weather conditions improved without affecting its integrity or overloading installation equipment.
A Numerical Method for Calculation of Ship-Ship Hydrodynamics Interaction in Shallow Water Accounting for Sinkage and Trim
Authors: Ren Huilong , Xu Chen , Zhou Xueqian , Sutulo Serge , Guedes Soares Carlos 
Published: November 2019

Abstract
Sinkage and trim, which often occur to ships moving in shallow water, do not only have an effect on the ship-ship hydrodynamic interaction forces, but also increase the risk of grounding. An algorithm based on the potential theory has been devised for real-time simulation of the hydrodynamic interaction between two ships in shallow water accounting for sinkage and trim. The shallow water condition is modeled using the mirror image method; while the sinkage and trim are solved iteratively based on the principle of hydrostatic balance, where a mesh trimming procedure is performed when the waterline is changed. Simulations are performed with and without accounting for the sinkage and trim, and comparison with experimental results shows a fair agreement.
Out-of-Roundness of the TurkStream Project Line Pipe
Authors: Selker Ruud , Liu Ping , Jurdik Erich , Chaudhuri Jay 
Published: November 2019

Abstract
When using stochastic data in a probabilistic engineering assessment it is common practice to fit the central portion of the data, using for example the Normal distribution. This generally works for predicting expected behaviour; however, it does not necessarily describe extreme behaviour very well.
Extreme value theory and more specifically the peaks-over-threshold method [1] is adopted to assess the extreme behaviour represented by the distribution’s tail. A generalized Pareto distribution is used to fit all samples exceeding a certain threshold value. Estimation of the distribution’s shape parameter provides valuable information on whether the upper tail of the fitted distribution has “finite” (having an endpoint) or “infinite support”.
Line pipe out-of-roundness affects weldability, fatigue performance and collapse resistance. Especially for deep water pipelines it is important to meet tight tolerances. Out-of-roundness data were evaluated and show finite support of the upper tail; however, the evidence is not as strong as the evidence that was found for the line pipe material strength [7]. Hence it is important to measure and confirm the out-of-roundness of every pipe joint during manufacture.
The degree of tail support can have a major effect on the calculated return period of failure events, particularly when related to low occurrence probabilities.
Numerical Study on Seakeeping Performance of a Damaged Ship
Authors: Cui Lu-Ning , Zheng Yi , Li Yinggang , Zhu Ling , Chen Mingsheng 
Published: November 2019

Abstract
Ships sailing in the sea may encounter collision, grounding or projectile impacting accidents, which may cause hull damage and subsequent compartment flooding. Due to the effect of the flooding water induced moment and the restoring moment, the damaged ship may have inclination and rolling motion. When the inclination or the rolling motion is too large, it may affect the safety and survivability of ship in navigation and cause severe casualties and property losses. In order to increase the navigation safety and survivability of the damaged ship, a numerical model is established based on the potential flow theory to investigate the seakeeping performance of the damaged ship in two scenarios, i.e., the case before ship damaged, and the case when the damaged ship reaching a relatively stable floating state. The heave, pitch and roll motion responses and corresponding wave-induced loads acting on the ship are analyzed in regular waves. In addition, the effects of the navigation speed and the wave direction on the seakeeping performance are also investigated.
Coupled Thermo-Elastic Analysis on Cross-Section of Umbilical Cables
Authors: Yan Jun , Hu Haitao , Su Qi , Lu Qingzhen , Yang Zhixun , Yue Qianjin 
Published: November 2019

Abstract
Umbilical cable is composed of electronic cables, optical cables, steel tubes and structural strengthening components, which can be regarded as a key industrial equipment integrating mechanical and electronic functions. Especially, when it is oriented at the power supply with a relatively high rated voltage, the power transmission will produce a large amount of heat with the sectional temperature rising up, which impacts on the material performance and mechanical responses of the cable and even the whole umbilical. Therefore, the thermo-elastic analysis is the critical technology in the cross-sectional design of umbilical cable. Analytical and numerical methods are proposed to conduct the thermo-elastic analysis of the cross-section. Firstly, the steady-state thermal analysis of cross-section of the umbilical cable is implemented, and the thermal field distribution with different cable ampacity is obtained. Then, the thermo-elastic coupled analysis of the cross-section is presented. It is found that the results are quite different from that of static mechanical analysis, which provide a helpful guide for the design of umbilical structures.
Wellhead Fatigue: Benefits of Structural Reliability Analysis Applied to Groups of Wells
Authors: Hørte Torfinn , Macke Michael , Aardal Andreas Buvarp , Reinås Lorents , Bjønnes Pål , Frimanslund Erik Kristian 
Published: November 2019

Abstract
This paper outlines the methodology when performing structural reliability analysis (SRA) for wellhead fatigue of a complete field compared to individual wells. The field consist of several well and template systems from different suppliers. Further this paper will emphasize on added knowledge that can arise from the field vs. well analysis approach. Finally, some advice and guiding on necessary prerequisites for launching a field SRA will be shared.
The methodology followed previous advices, with the added element that all wells were categorized depending on similarities in well design. Furthermore, a number of local finite element analyses for a specified systematic set of variations in input parameters have been performed by relevant equipment manufacturers to calculate the fatigue stress at critical hot spots (load-to-stress curves).
Similar actions on loads had to be performed. A comprehensive set of global load analyses for each of the different rigs that have been operating on the field where needed to assess the cyclic fatigue loads from historical operations on each well. Finally, global and local analysis results were then gathered, and used as input to the SRA combined with a response surface technique.
The additional effort for making the underlying global and local analyses covering all wells, and not only a single well, is limited for a given type of wellhead system. The field results now provide the operator with an improved basis for planning of future operations on the field, and enables optimization of the drilling plan and utilization of rigs throughout the varying environmental conditions for different seasons of the year and different operations, while managing the associated risk.
Biofouling Characterization and its Effect on Resistance of Surface Ship
Authors: Thomas Della , Surendran S. , Vasa Nilesh J. 
Published: November 2019

Abstract
Manufacture of coatings to tackle the biofouling menace has been of prime concern for the shipping industry since industrial revolution. Even though many types of coatings exist in the market, they have not been able to wipe out the problem of biofouling completely. The proposed approach which combines both the resistance due to biofouling on ships, as well as biofouling characterization, will surely serve as a critical input for the manufacture of efficient anti-fouling coatings. Resistance simulations have been carried out for a tanker ship by Maxsurf® wherein the hull fouling effect has been accounted for by modified ITTC 1978 empirical formula considering roughness. Different draft conditions were relied upon to find out the resistance at various Froude numbers. The fouling growth conditions considered are small and medium calcareous fouling. The simulated results also have been validated by towing tank experiments, for no-foul condition, for speeds varying from 0.3 to 1.1 m/s and different drafts. The additional power requirement was determined for various loading conditions and speed ranges.
Review of the In-Air Fatigue Behaviour of CRA Clad and Lined Pipe
Authors: Johnston Carol , Crump Jenny 
Published: November 2019

Abstract
Pipe internally clad or lined with corrosion resistant alloy (CRA) is used offshore when production fluid contains H2S and/or CO2 to protect the carbon-steel pipe from corrosion. Girth weld classification in standards such as BS7608 and DNVGL-RP-C203 do not specifically include clad and lined pipes but their fatigue performance is relevant to designers of these pipelines. This paper first reviews available literature on the in-air fatigue performance of clad and lined girth welds. Data from the literature as well as full scale resonance fatigue results from tests carried out at TWI are then analysed so that recommendations can be made on a suitable fatigue classification. Finally, areas are highlighted where more research into clad and lined pipe is needed.
Axial and Moment Carrying Capacity of Split Sleeve Grouted Connections for Repair of Tubular Members
Authors: Vignesh Chellappan N. , Nallayarasu S. 
Published: November 2019

Abstract
The tubular members damaged by ship impact or falling objects require repair and rehabilitation in offshore structures. The repair of damaged underwater tubular member using welding is hazardous and expensive and hence alternative connection methods such as grouted clamp techniques have been in use for many decades. The existing guideline on the design of grouted connections especially under axial tension and moment is very limited and requires further study. The load transfer mechanism of grouted clamps depends on various geometric parameters and bond between clamp and parent member. A comprehensive study on split sleeve grouted connection for load transfer between two parts of tubular members has been investigated and presented.
Numerical simulation of split sleeve grouted connection has been carried out using finite element model of tubular member – sleeve through bond strength of grout. The numerical model has been validated using existing guidelines and further parametric study has been carried out. The parametric study includes geometric parameters such as diameter to wall thickness ratio of split sleeve, sleeve friction length, grout strength and grout shrinkage. The simulations have been carried out for combination of axial tension and moment loading.
An Investigation of the Effect of Biomimetic Tubercles on a Flat Plate
Authors: Marino Alessandro , Atlar Mehmet , Demirel Yigit K. 
Published: November 2019

Abstract
This paper describes the investigation, by means of Computational Fluid Dynamics (CFD), of the effect of biomimetic tubercles on the hydrodynamics of a fully submerged flat plate. The application of these tubercles takes inspiration from the features of the humpback whale (Megaptera Novaeangliae). These huge marine mammals are capable of quick and agile movements in the water, despite their bulky bodies. Researchers investigated the causes of this ability by studying some peculiar somatic characteristics of these animals, in particular the tubercles on the leading edge of their pectoral fins. These tubercles were applied in the form of sinusoidal perturbations of the leading edge of wing profiles and foils, and they proved to cause a positive effect on the overall performance.
The aim of this paper is to investigate another type of tubercles, which appear in the shape of bumps on the whales head. The effect of these tubercles has not been studied yet, and this paper presents a study on the fundamental phenomena they generate in the water flowing on the surface of a flat plate. The tubercles are modelled as axisymmetric sinusoidal bumps placed on the flat plate. Different combinations of these tubercles are studied, in order to assess what the effect of a single tubercle is, and how more tubercles interact when they are placed closed to each other, in different configurations (number of tubercles and relative position). In addition, a systematic study of the effect of a single row of tubercles spanning perpendicularly to the flow is carried out. The tubercles change systematically in amplitude and position along the plate.
One further objective of this paper is to investigate if an optimised application of the biomimetic tubercles can lead to a drag reduction for the flat plate. Preliminary simulations show that the rows of tubercles interact with the boundary layer by modifying the pressure distribution, velocity and direction of the flow. The tubercles appear to generate vortices that are similar to those created by sinusoidal tubercles on the leading edge of foils, which tend to thin the boundary layer. A change in the total drag of the plate with tubercle is also noticeable, which even decreases from the baseline (flat plate with no tubercles), at certain combinations of position and tubercle amplitude.