bluuebunny/crossref_metadata_2025_split huggingface dataset:
Waves in the Great Pacific Garbage Patch: Cross Validation of Three Measurement Techniques and Two WW3 Models
Authors: Wrenger Hendrik , Sainte-Rose Bruno , Soares Ivan 
Published: December 2020

Abstract
The Ocean Cleanup Foundation is developing floating barrier systems to concentrate and extract buoyant plastic from the global accumulation zones. To analyze and improve the efficiency of such cleanup systems, access to accurate Metocean conditions is inevitable. The Ocean Cleanup runs its own implementation of WAVEWATCH III® to have full control over the spatiotemporal resolution and to have access to all critical output, such as 2D wave spectra or Stokes drift at the surface to only name two examples.
We present here an experimental campaign that was carried out during the deployment of the first two systems in the Pacific to A) validate the performance of both a GFS and CFSR forced wave model, 1000+nm from available NOAA buoys and B) intercompare the wave measurements from an unmanned surface vessel (USV) with those from wave buoys and a vessel based X-Band radar. The USV is the most feasible tool to collect long periods of data along the system trajectory and our preferred option in the long run. We zoom into one day to review in detail the various data sources, their comparability and employed post processing techniques. We present a preliminary comparison of integral wave parameters for the entire campaign (2272hrs/data points) and discuss further steps towards a more complete investigation.
The preliminary comparison suggests that the USV and wave buoy data compare rather well. The largest differences are seen in wave periods. We obsen’e small differences between the GFS and CFSR forced model, both compare well with the field measurements.
High-Fidelity Modelling of Floating Offshore Wind Turbine Platforms
Authors: Burmester Simon , Vaz Guilherme , el Moctar Ould , Gueydon Sebastien , Koop Arjen , Wang Yu , Chen H. C. 
Published: December 2020

Abstract
There are already several examples of commercially operating floating offshore wind turbines (FOWTs) delivering electricity to the grid. These devices operate usually in harsh environments due to high waves, strong winds and currents. Guaranteeing the survivability of these complex and expensive constructions is crucial but not straightforward, and this may be partially controlled by the associated hydrodynamic damping. FOWT structures are still designed and analysed using potential-flow and empirical tools. However, nowadays, almost all fields of maritime problems are seeing an increased use of higher-fidelity viscous-flow tools (CFD, or Computational Fluid Dynamics), due to its increased modelling accuracy. Therefore, in this work, a FOWT is analysed in detail using CFD with emphasis on the hydrodynamic damping. This damping arises due to wave radiation, skin friction, eddy making and lift, and drag of the mooring lines. The CFD associated turbulence model influences largely the eddy making and skin friction components of the damping. Moorings are also a critical issue when assessing the damping of a floater. Catenary moorings are towed along with the motion of the floater and induce loads (drag and inertia) on the lines, effects which cannot be represented by static or quasi-static approaches. And numerical errors, often neglected or not quantified, can influence all the previous aspects and the final accurate prediction of the structure damping. In this paper, all these aspects are investigated by performing CFD decay tests, and their contribution quantified in terms of linear and quadratic damping components. The following issues were found to have a major contribution to the hydrodynamic damping and consequently on the motions of the platform: numerical discretisation (temporal and spatial), Reynolds number, free surface, turbulence and accurate mooring modelling.
Additive Manufacturing: Challenges and Solutions for Marine and Offshore Applications
Authors: Qiao Dongchun , Wang Bo , Gu Hai 
Published: December 2020

Abstract
As a rapidly developing technology, the expanded capability of Additive Manufacturing (AM) allows implementation into the marine and offshore industries. Qualification of metal AM part may need detailed test plans and test results in order to meet the design requirements with a certain level of reliability. Approval may also be needed in accordance with regulation codes and class rules.
However, challenges and gaps remain between the current metal AM technology level and marine and offshore applications. In this paper, two major categories of metal AM processes are discussed: powder bed fusion (PBF) and directed energy deposition (DED) with powder or wire as raw materials and laser, electronic beam (E-beam) or arc as heat source. The main challenges are also investigated in this study as follows: 1) Optimization of build cost and part quality by selection of appropriate process; 2) Performance of the part under static and cyclic loading; 3) Evaluation of the effects of corrosive environments (seawater); 4) Lack of standardization of the AM process for quality control. This paper addresses possible solutions for these challenges and provides qualification framework for metal AM parts to be implemented into marine and offshore applications.
Generation of 3-hr Long-Crested Waves of Extreme Sea States With HOS-NWT Solver
Authors: Canard Maxime , Ducrozet Guillaume , Bouscasse Benjamin 
Published: December 2020

Abstract
The accurate control of wave fields generated in experiments and numerical simulations is of great interest for the ocean engineering community. In the context of wave-structure interactions, the recommended practices of classification societies are indeed based on the definition of a wave spectrum, that needs to be reproduced. The present work intends to address this problem from the numerical point of view, using a Numerical Wave Tank equipped with a wavemaker and an absorbing beach, based on the High-Order Spectral method (HOS-NWT). The challenging case of the generation of 3-hours long-crested extreme sea states is studied in details. An iterative procedure to reproduce a target wave spectrum at a given distance from the wavemaker is proposed. The quality of the sea state obtained is evaluated using several criteria defined from spectral quantities. A validation is first performed with a highly nonlinear but non-breaking sea-state. Statistical crest distributions obtained are compared with the Forristall and Huang distributions [1,2]. Then, the Gulf of Mexico 1,000 Year Return Period wave condition is generated. This corresponds to an extreme sea state with significant wave breaking occurrence. The numerical solver needs to be able to account for this phenomenon [3]. The Tian breaking model [4, 5] is calibrated to realistically reproduce the dissipation due to breaking, with particular attention paid to the spatial discretization, enlightening its significant effect on breaking model actions. Consequences on the iterative correction process are studied. The computed statistical quantities appear to be significantly different changing the spatial discretization, while the wave energy spectrum stands the same. It questions the relevance of the characterization of a sea state with the sole wave energy spectrum.
How Reliability Based Design Can Increase Operating Window for 20k Drilling Risers
Authors: Pilisi Nicolas , Lewis David 
Published: December 2020

Abstract
The objective of this paper is to answer the questions posed and in doing so create an awareness of the necessity to use reliability based design when looking at vessel operating windows rather than working stress design which has been used for marine drilling riser analysis and design for many decades. In answering, this paper presents several case studies of drilling riser stresses and operating windows when drilling to access reservoirs with pressure greater than 15,000 psi and up to 20,000 psi. This paper examines the need for full and proper use of a more probabilistic design over working stress design for a set of water depth, subsea equipment, environments and loading conditions.
Hydrodynamic Study on the Damping Characteristics of Cylindrical FPSO With the Heave Plate
Authors: Jiang Meirong , Li Da , Wang Zhongchang , Jia Xu , Yu Yang 
Published: December 2020

Abstract
The heave plate setting up on the hull can effectively improve the movement performance of the cylindrical FPSO. In the research process of its damping effect, a reliable model is also needed to do the further study besides the physical model test. The objective of the present work is to establish a reasonable hydrodynamic model to investigate the damping behavior of the cylindrical FPSO with the heave plate. Based on the k-ε turbulence model and the VOF method, a three-dimensional hydrodynamic model are established to simulate the movement of the cylindrical FPSO in the offshore environment. A typical annular thin plate is set up on the bottom side of the hull as the damping structure. The available experimental data are adopted to preliminarily verify the established model. The structural pattern of the damping plate is optimized considering different widths of the plate and excitation modes. The motion amplitude, natural period and damping coefficient can be extracted from the computation and be analyzed to obtain the hydrodynamic performance of the cylindrical FPSO. From the simulation and verification, the numerical results are agreed quite well with the measured values in the model test, which proves that the model is reliable. When the cylindrical FPSO oscillates in the water body, the vortexes are generated around the heave plate and shed from it, which are the primary reason for the increase of the viscous damping. As the width of the heave plate increases, the damping coefficient and ratio increase gradually, but the natural period of the structure is basically unchanged. As for the amplitude of the motion, the variation of the damping coefficient is not obvious, and the natural period of the structure is also basically unchanged. When the motion amplitude is relatively small, the damping ratio increases gradually with the increase of the motion amplitude; while the motion amplitude is large, the amplitude increment of damping ratio tends to be flat, or even decreases. This hydrodynamic study is meaningful for the researcher and engineer to further understand the damping characteristics of the cylindrical FPSO. It can also provide some technical supports for the structural optimization design of the heave plate.
Fatigue Design of Hybrid Welded Steel Beams
Authors: Van Wittenberghe Jeroen , Van Den Abeele Filip 
Published: December 2020

Abstract
Hot rolled sections such as I- and H-beams are commonly used as structural elements in offshore platforms. They exhibit a superior fatigue life compared to welded sections due to smooth corners and the absence of welds between the flange and web plates. Hence, when loaded in fatigue, the butt welds joining different sections are the hotspots in the design.
Due to the size of the rolling installations, the maximum height for such sections is limited. To overcome these limitations, a hybrid welded beam concept is studied. This concept consists of 2 hot rolled T-sections with a plate welded in between to form an H-beam with increased section height. The advantage of this approach is that it maintains the smooth corners of the hot rolled sections and places the longitudinal welds closer to the neutral axis of the beam where the stress levels in bending are reduced compared to the flange-web interface. Hence, the butt weld between different beam sections remains the hotspot instead of the longitudinal weld.
In the present work the fatigue design of such hybrid welded beams is studied. As part of this research, an efficient experimental assessment methodology is proposed. Fatigue tests are performed on a large-scale resonant bending test setup allowing a testing frequency of around 30 Hz. Tests are performed on HISTAR HE girders with a section height of 696 mm and 524 mm. As a reference, fatigue tests are performed on hot rolled HE beams joined by butt welding. Hybrid welded beams will be tested in the same setup at a later stage. During the tests, fatigue crack initiation is detected using an acoustic emission system. Further crack propagation is monitored through local strain measurements and by intermediate inspections during the tests. In addition, the beach marking method is applied, allowing to investigate the evolution of the crack front by post-mortem analysis.
Anomaly Criteria for General Visual Inspection of Subsea Flexible Pipes
Authors: Tadjiev Damir 
Published: December 2020

Abstract
For flexible pipes in subsea applications, General Visual Inspection (GVI) by Remotely Operated Vehicles (ROV) remains the most common inspection method that is used on a routine basis. It enables verification of pipe configuration or layout and also helps to identify any areas of concern indicative of an increased risk of in-service failure.
The success of ROV GVI chiefly relies on the anomaly criteria used, these help inspectors to identify any areas of concern, which can then be assessed by a competent person to ensure any threat to the integrity of an inspected component is identified and addressed.
Currently there are no commonly accepted anomaly criteria for ROV GVI of flexible pipes. As a result there is no consistent approach between different operators and experience shows that the inspection approach and anomaly criteria are often adopted from what has traditionally been used for rigid pipes. Since flexible pipes have different design and associated failure threats and mechanisms to rigid pipe, use of this approach may result in under or over inspection of flexible pipes.
This paper presents a set of anomaly criteria for ROV GVI of flexible pipes. The criteria were developed using the experience and lessons learned from a population of approximately 350 flexible pipes from two different manufactures operating in deep waters of the UKCS for over a period of 20 years. The criteria cover dynamic flexible risers and associated ancillary equipment, seabed flexible flowlines and jumpers. The applicability of the proposed anomaly criteria to other systems, the benefits of having commonly accepted anomaly criteria, the anomaly detection capability of ROV GVI and the reporting of anomalies are also discussed.
Analysis of Bore Characteristics Using KdV-Based Nonlinear Fourier Transform
Authors: Bruehl Markus , Wahls Sander , Barranco Granged Ignacio , Liu Philipp L.-F. 
Published: December 2020

Abstract
Bores propagating in shallow water transform into undular bores and, finally, into trains of solitons. The observed number and height of these undulations, and later discrete solitons, is strongly dependent on the propagation length of the bore. Empirical results show that the final height of the leading soliton in the far-field is twice the initial mean bore height. The complete disintegration of the initial bore into a train of solitons requires very long propagation lengths, but unfortunately these required distances are usually not available in experimental tests or nature. Therefore, the analysis of the bore decomposition for experimental data into solitons is difficult and requires further approaches. Previous studies have shown that by application of the nonlinear Fourier transform based on the Korteweg–de Vries equation (KdV-NFT) to bores and long-period waves propagating in constant depth, the number and height of all solitons can be reliably predicted already based on the initial bore-shaped free surface.
Against this background, this study presents the systematic analysis of the leading-soliton amplitudes for non-breaking and breaking bores with different strengths in different water depths in order to validate the KdV-NFT results for non-breaking bores, and to show the limitations of wave breaking on the spectral results. The analytical results are compared with data from experimental tests, numerical simulations and other approaches from literature.
Verification and Validation of CFD Uncertainty Analysis Based on SST K-ω Model
Authors: Zhang Li , Chen Weimin , Chen Jianting , Zhou Chuanming 
Published: December 2020

Abstract
CFD uncertainty analysis is a process to quantify the accuracy of numerical simulation results, and it is also a research hotspot in the past decades. ITTC(2017) requires uncertainty analysis of ship CFD simulation results, that is, verification and validation. In this paper, with reference to the recommended procedures by ITTC, the uncertainty of the CFD numerical simulation results of ship model resistance was analyzed. Based on the SST k-ω turbulence model, the Y+ values near the wall were set to 60,120,240, respectively. And for each and Y+ value, three different sets of grid densities were set respectively, and the uncertainty was analyzed. The results show that: 1) the results of Y+ at 60 and 120 were not validated, and the results at 240 was validated, 2) the selection of Y+ value has a significant effect on the numerical results, 3) increasing the mesh density can make the result converge, but it is not sure to get the result with the least error. Through the uncertainty analysis of CFD results, it is helpful to find a method to improve the accuracy of the numerical results.
Stable Triple-Layer Lubricated Pipeline Flow
Authors: Sarmadi Parisa , Hormozi Sarah , Frigaard Ian A. 
Published: December 2020

Abstract
Recently we have introduced a novel methodology for efficient transport of heavy oil via a triple-layer core-annular flow [1]. Pumping pressures are significantly reduced by concentrating high shear rates to a lubricating layer, while ideas from visco-plastic lubrication were used to eliminate interfacial instabilities. We purposefully position a shaped unyielded skin of a visco-plastic fluid between the transported oil and the lubricating fluid layer. The shaping of the skin layer allows for lubrication forces to develop and balance the density difference between the fluids. Here we show an explicit advantage of the proposed method. Essentially the method can give stable flows for a very wide range of fluid input ratio, although not all will produce the desired reduction in frictional pressure losses. Additionally, we use the extensional flow method derived in [2] to estimate the required yield stress to maintain the skin completely unyielded.
Experimental Investigations on the Residual Strength of Corroded Steel-Stiffened Plates
Authors: Park Sang-Hyun , Shin Hyun Kyoung , Kim Jae-Shin , Cho Sang-Rai , Jang Yong-Su , Baek Nam-Ki , Park Dong-Ki 
Published: December 2020

Abstract
In this study, the tensile and compressive behaviours of corroded steel-stiffened plates were experimentally investigated, and the effects of pitting- and grooving-corrosion damage on the residual strengths of corroded stiffened plates were evaluated. Two series of tests were conducted for this study: one involved tensile test on specimens having natural corrosions and artificially machined corrosions, and the other involved compression tests on damaged stiffened plates having artificially machined corrosions. Naturally corroded tensile specimens were obtained from an aged ship. The profiles of the naturally corroded tensile specimens were measured using a three-dimensional (3-D) scanner and a dial thickness gauge. Tensile tests were conducted on nine naturally corroded and fifteen artificially machined specimens. Compression tests were performed on seven stiffened plates having artificially machined corrosion damage. Pitting- and grooving-corrosions were considered in the compression tests. Before these tests, the initial shape imperfections of the stiffened plate models were measured using a 3-D scanning machine. Test results including load-displacement relationship and the ultimate strength under compressive loads were analysed. Finite element (FE) modelling and analyses were performed in this study using commercial software CATIA and ABAQUS. The outputs of numerical analyses were compared with the corresponding test results, and a reasonable agreement between the test results and numerical predictions is shown.
Numerical Simulation and Experiments of Flow-Induced Oscillations of Single-Cylinder With Large Passive Turbulence Control
Authors: Li Ningyu , Park Hongrae , Sun Hai , Bernitsas Michael M. 
Published: December 2020

Abstract
Passive turbulence control (PTC) is being used in the Marine Renewable Energy Laboratory (MRELab) of the University of Michigan to enhance flow induced oscillations (FIO) of cylinders in the VIVACE (Vortex Induced Vibration for Aquatic Clean Energy) Converter. Large PTC triggers VIV and galloping at lower flow speeds for energy harvesting. Currently, FIO of cylinders with large PTC for high Re has received limited attention and, particularly, the effect of variable PTC height on FIO of cylinders. The vast majority of ocean currents, rivers, and tides are too slow for Marine Hydro Kinetic (MHK) energy technologies to harness it. In order to enhance FIO and to initiate galloping earlier, a circular cylinder is geometrically modified using straight strips placed on the cylinder surface symmetrically PTC strips on the cylinder effectively change the flow properties. In the present study, the FIO of a single-cylinder with large PTC, on end linear-springs, is modelled and simulated using a Fluid-Structure Interaction (FSI) code. Results are verified by corresponding experimental data. Results show that VIV onset occurs at lower Re for large-PTC cylinder in comparison with lower-PTC cylinder. Contrary to smooth cylinders for which the amplitude ratio is small in the transition region between VIV and galloping, application of large PTC leads to high amplitude response in the transition region. The mechanism behind this observation is the further departure of the geometry from the smooth circular cylinder. The latter does not exhibit galloping due to flow and geometric symmetry in all directions. Moreover, in the galloping region, the amplitude ratio increases with the height of PTC. Earlier onset of galloping and enhancement of geometric asymmetry support this observation as well.
Systematic Measures to Cope With Offshore Drilling Hazards: An Interpretive Structural Modeling Approach
Authors: Ali Liaqat , Jin Shan , Bai Yong 
Published: December 2020

Abstract
The process of offshore drilling faces several challenges. The process of mixing of water and oil results in issues that lead to the contamination of ocean water. Therefore, this study focuses on the hazards and the measures taken to cover up those hazards of offshore drilling. There are types of offshore drilling hazards such as health hazards and safety hazards. In connection to identify the hazards facing in offshore drilling and taking measures to prevent these hazards, ISM (interpretive structural modeling) technique is used. Data is collected through extensive literature review and by conducting interviews from Japan and China. Experts from academia and industry specialists are approached for interview. Eight important Measures to prevent the hazards due to offshore drilling have been identified. And the relationship among these measures are depicted by constructing SSIM (structural self-interaction matrix). The next step of ISM technique which is reachability matrix, developed which also establish the driving and dependence power of each variable. After reachability matrix a diagram is discussed where the measures are depicted in relation to their dependency, drive and independency levels, which show the influence of each measure with other. This study is valuable in the field of offshore drilling for top managers in decision making and for literature review study. Further, this study has some limitation, if the contributions of experts from other countries would have been exerted in our research that may came up with more measures for the prevention of hazards encounter in Offshore oil drilling. Further, quantitative analysis should be considered to find the absolute values to evaluate the measure.