bluuebunny/crossref_metadata_2025_split huggingface dataset:
AMBEMAR-DSS: A Decision Support System for the Environmental Impact Assessment of Marine Renewable Energies
Authors: Guinda Xabier , Puente Araceli , Juanes José A. , Royano Francisco , Fernández Felipe , Vega Marco A. , García Andrés , García Javier , Aragón Germán , Abascal Ana J. , Otero César , Manchado Cristina , Gómez-Jauregui Valentín , López Joaquín , Monteoliva Agustín 
Published: September 2018

The high energy demand and the threat of climate change have led to a remarkable development of renewable energies, initially through technologies applied to the terrestrial environment and, recently, through the awakening of marine renewable energies. However, the development of these types of projects is often hampered by failure to pass the corresponding environmental impact assessment process.
The complexity of working in the marine environment and the uncertainties associated with assessing the impacts of such projects make it difficult to carry out objective and precise environmental impact assessments.
AMBEMAR-DSS seeks to establish a basis for understanding and agreement between the different stakeholders (project developers, public administrations, environmental organizations and the public in general), in order to find solutions that allow the development of marine renewable energies, minimizing their environmental cost. For this purpose, a DSS is proposed which, based on cartographic information and using objective and quantifiable criteria, allows comparative assessments and analyses between different project alternatives. The analytical procedures used by the system include, among others, hydrodynamic modeling tools and visual impact simulators. In addition, impacts on marine species are assessed taking into account intrinsic ecological and biological aspects. The magnitude of the impacts is quantified by means of fuzzy logic operations and the integration of all the elements is carried out by an interactive multi-criteria analysis. The results are shown in tables, graphs and figures of easy interpretation and can be also visualized geographically by means of a cartographic viewer.
The system identifies the main impacts generated in the different phases of the project and allows establishing adequate mitigation measures in search of optimized solutions. The establishment of the assessment criteria has been based on the abundant, but dispersed, scientific literature on the various elements of the system and having the opinion of experts in the various fields. Nevertheless, the DSS developed constitutes a preliminary basis on which to build and improve a system with the input of researchers, promoters and experts from different disciplines.
Flexible Flowline Walking Tendency on Seabed With Longitudinal Undulations and Transverse Gradients
Authors: Roberts Graeme , Sriskandarajah T. , Colonnelli Gianluca , Roux Arnaud , Roy Alan , Ragupathy P. 
Published: September 2018

A method of carrying out a combined axial walking and lateral buckling assessment for a flexible flowline has been developed using finite element analysis. The method overcomes limitations of screening assessments which could be inconclusive when applied either to a flexible flowline on an undulating seabed with transverse gradients or to one that buckles during hydrotest.
Flexible flowlines that were to be surface-laid on a seabed with longitudinal undulations and transverse gradients were assessed using the method. The flexible flowlines were simulated in their as-laid state, and the simulation incorporated hydrotest pressure and the pressure & temperature gradients and transients associated with multiple start-ups. The objective was to quantify the axial walking and lateral slip tendency of the flexible flowlines and the impact that walking might have on the connected end structures. The lateral buckle locations predicted by finite element analysis were compared to a post-hydrotest survey and the radius of curvature from analysis was compared to the minimum bend radius of the flexible.
Cutting of Fluid Saturated Rock: A Tentative Explanation of Dilation vs. Compaction
Authors: Helmons Rudy L. J. , van Rhee Cees , Detournay Emmanuel , Alvarez Grima Mario 
Published: September 2018

Traditionally, rock cutting models for land-based and shallow water applications assume that the rock is cut under atmospheric and dry conditions. For deep sea applications this assumption is not valid, especially because the hydrostatic pressure can be of the same order of magnitude as the unconfined compressive strength of the rock. Therefore it is necessary that both the effect of hydrostatic pressure and the presence of a pore fluid are included in the rock cutting models as well.
This paper focuses on extension of the existing phenomenological rock cutting theory for deep sea applications. The suggested improvements of the model are based on observations from both experiments and simulations. The ideas presented can be helpful for the design of equipment for the drilling, deep sea mining and subsea trenching industries.
Internal Surface Crack Growth in Offshore Rigid Pipes Reinforced With CFRP
Authors: Li Zongchen , Jiang Xiaoli , Liu Zhiping , Hopman Hans 
Published: September 2018

Rigid pipelines have been widely applied in offshore oil & gas operation and transmission industries on account of their structural simplicity, cost-effectiveness, ease of installation and maintenance. However, surface cracks frequently appear in the internal surface of rigid pipes due to dynamic loads or hydrogen embrittlement, etc. Under dynamic fatigue loads, surface cracks may continue to propagate and finally develop into penetrated cracks, which may cause leakage and serious accidents.
Fiber-reinforced polymer (FRP) strengthening technology is already a reliable technique for structure maintenance in onshore pipelines and penetrated cracks in load-bearing circular hollow sections (CHS). Nevertheless, there are very limited systematic investigations of surface crack in rigid pipes reinforced with FRP, which has a remarkable significance for offshore rigid pipes.
This paper aims to understand the mechanism of semi-elliptical surface crack growth in the internal surface of rigid pipes under fatigue bending moment reinforced with FRP. Stress intensity factors along the crack front are computed through finite-element (FE) models, which are validated by experimental data from references. The influence of wrapping orientation of CFRP are discussed as well. The numerical results show that under CFRP reinforcement, surface crack growth rate decreases significantly which ensures the safety use of rigid pipes in offshore industry.
Instantaneous Center of Rotation in Pitch Response of a FPSO Submitted to Head Waves
Authors: Costa Daniel de Oliveira , Fernandes Antonio Carlos , Sales Junior Joel Sena , Asgari Peyman 
Published: September 2018

When under influence of an incident wave system, any floating body presents a general motion with all six degrees of freedom, unless it presents some kind of restrains on it. For a free moving body, the center of rotation will depend on the force distribution and might not coincide with its center of gravity. For long and slender floating structures, such as FPSO platforms, a small change in the center of Pitch rotation would result in significant change in the overall motions in its fore and aft regions. Therefore, it is of high importance to obtain a better understating of the instantaneous position of the body center of rotation in Heave and Pitch response.
This paper investigates the position of the Instantaneous Center of Rotation in Pitch Response of a scaled down model of a FPSO platform under different regular wave conditions. The investigation uses basic kinematics equations for rigid body, defining the 6 degrees of freedom of the rigid body motion from a finite number of markers installed in the model. A high quality tracking system captures the markers positions in order to define the rigid body at each instant of time. For an initial approach, the study considers the response due to head waves seas with experimental validation.
The Development of an Enhanced Riser Management System Including Dynamic Watch Circles for Drilling Operations in Harsh and Ultra-Deepwater Environments
Authors: Poirier Martin , Russo Massimiliano , Srikonda Rohit , Karlstad Martin , Abelsen Kjetil , Kling Curt 
Published: September 2018

The operating boundaries and associated watch circles of an offshore drilling campaign are traditionally assessed by technical analysis including simulations of rig, riser and conductor/casing response to determine the mechanical limits and confirm the design limits. V a r i o u s inputs such as weather conditions, mud weights, tension settings and other critical operational aspects have to be defined in the office. The obtained results are then incorporated into a paper based Well Specific Operating Guidelines (WSOG). This traditional WSOG approach may prove particularly limiting in harsh environment and ultra-deepwater operations [1]. Traditional WSOG limits can be overly conservative, predicting excessive non-productive time and, in some cases, indicating too high risks. In some occasions these aspects may prevent planned drilling operations from being sanctioned.
In 2016, Total Exploration & Production (TEP) drilled a complex well at a record water depth of 3,404 meters in challenging environmental conditions offshore Uruguay, with up to Beaufort 10 gales, 16m maxima waves and significant ocean current often above 2 knots. These extreme conditions for the drilling campaign highlighted the necessity of an enhanced Riser Management System (RMS). This paper presents the enhanced RMS, which includes among other features, the upgrade of the BOP inclinometers with high quality sensors, soil stiffness tracking, casing monitoring, wellhead integrity and fatigue monitoring, VIV detection functionality and enhanced operability monitoring. The paper further introduces the use of Dynamic Watch Circles (DWC) and Dynamic Operability Envelopes (DOE) based on real time monitored data and actual weather conditions. Finally, the paper discusses the potential benefits of implementing an electronic WSOG (eWSOG™) replacing the traditional WSOG for extreme drilling operations.
Semi-Empirical Single Realization and Ensemble Crest Distributions of Long-Crest Nonlinear Waves
Authors: Huang Zhenjia (Jerry) , Zhang Yu 
Published: September 2018

In wave basin model test of an offshore structure, waves that represent the given sea states have to be generated, qualified and accepted for the model test. We normally accept waves in wave calibration tests if the significant wave height, spectral peak period and spectrum match the specified target values. However, for model tests where the responses depend highly on the local wave motions (wave elevation and kinematics) such as wave impact on hull, green water impact on deck and air gap tests, additional qualification checks may be required. For instance, we may need to check wave crest probability distributions to avoid unrealistic wave crest in the test. To date, acceptance criteria of wave crest distribution calibration tests of large and steep waves of three-hour duration (full scale) have not been established. Two purposes of the work presented in the paper are:
1. to define and clarify the wave crest probability distribution of single realization (PDSR) and the probability distribution of wave crest for an ensemble of realizations (PDER) of a given sea state in order to use them appropriately; and
2. to develop semi-empirical probability distributions of nonlinear waves for both PDSR and PDER for easy, practical use.
We found that in current practice ensemble and single realization distributions have the potential to be misinterpreted and misused. Clear understanding of the two kinds of distributions will help appropriate offshore design and production unit performance assessments. The semi-empirical formulas proposed in this paper were developed through regression analysis of crest distributions from a large number of sea states and realizations. Wave time series from potential flow simulations, computational fluid dynamics (CFD) simulations and model test results were used to establish the probability distributions. The nonlinear wave simulations were performed for three-hour duration assuming that they were long-crested. The sea states are assumed to be represented by JONSWAP spectrum, where a wide range of significant wave height, peak period, spectral peak parameter, and water depth were considered. Coefficients of the proposed semi-empirical probability distribution formulas, comparisons among crest distributions from numerical simulations and the semi-empirical formulas are presented in this paper.
Equilibrium Position Analysis for Offloading Operations With Turret-Moored FPSO
Authors: Huang Alex S. , Moreno Felipe M. , Tannuri Eduardo A. , Câmara Joselito G. A. 
Published: September 2018

With the expansion of oil exploration in deep waters, assessing the risks associated with offloading operations becomes essential in preventing accidents that may cause huge environmental disasters.
In this paper, it will be studied the system composed of a turret-moored FPSO connected to a shuttle tanker which is assisted by a tug boat to maintain its position during an offloading operation.
Using environmental data collected over a period of 6 years, from 2004 to 2009, from the Campos Basin in Brazil, it was calculated the equilibrium positions of the system considering its constraints (vessels have to keep a minimum alignment), and verified the stability of those equilibrium points for all the given conditions.
The results obtained were simplified and grouped into operational rules using machine learning classification techniques.
Based on this static analysis, it was calculated the FPSO headings probabilities during offloading operation and the expected down time of operation in the Campos Basin.
Benchmark for the Sources of Uncertainty in Extreme Wave Analysis
Authors: Wada Ryota , Waseda Takuji 
Published: September 2018

This paper discusses the uncertainty in extreme wave analysis from different sources. Poor data quality and small sample size will lead to uncertainty in the extreme wave analysis. Extreme value estimation methods are developed based on various assumptions, and each would lead to unique estimation results. In addition, the cause of extreme waves varies among regions, directly affecting the extreme behavior. The aim of this study is to provide insight into how the uncertainty of extreme wave estimation is influenced by the different source of uncertainty, namely data uncertainty, method selection and extreme behavior at each location.
Key parameters to describe the extreme wave events are the frequency of occurrence and its tail-behavior. We use these two parameters as a benchmark to assess the extreme wave characteristics. We focus on four regions, namely Gulf of Mexico, North Sea, Adriatic Sea, and North West Pacific. Meteorological cause of extreme events and known extreme wave behavior are reviewed based on previous studies. Model inter-comparison revealed the shortcomings of wave models to reproduce extreme wave events, and the magnitude of data error was unique to each location.
Numerical experiments were conducted to evaluate the possible impact from poor data quality and small sample size on epistemic uncertainty. Case study based on representative parameters of Gulf of Mexico and North Sea revealed the difference between two locations. These results provide a benchmark for the source of uncertainty and its impact on extreme wave analysis. Among them, extreme waves dominated by tropical cyclones were most vulnerable to have large epistemic uncertainty. The importance to adequately quantify epistemic and aleatory uncertainty is reconfirmed.
Hydrodynamic Interactions of the Truncated Porous Vertical Circular Cylinder With Water Waves
Authors: Ouled Housseine Charaf , Malenica Sime , De Hauteclocque Guillaume , Chen Xiao-Bo 
Published: September 2018

Wave diffraction-radiation by a porous body is investigated here. Linear potential flow theory is used and the associated Boundary Value Problem (BVP) is formulated in frequency domain within a linear porosity condition. First, a semi-analytical solution for a truncated porous circular cylinder is developed using the dedicated eigenfunction expansion method. Then the general case of wave diffraction-radiation by a porous body with an arbitrary shape is discussed and solved through Boundary Integral Equation Method (BIEM).
The main goal of these developments is to adapt the existing diffraction-radiation code (HYDROSTAR) for that type of applications. Thus the present study of the porous cylinder consists a validation work of (BIEM) numerical implementation. Excellent agreement between analytical and numerical results is observed. Porosity influence on wave exciting forces, added mass and damping is also investigated.
Combining Physics-Based and Data-Driven Models for Estimation of WOB During Ultra-Deep Ocean Drilling
Authors: Kaneko Tatsuya , Wada Ryota , Ozaki Masahiko , Inoue Tomoya 
Published: September 2018

Offshore drilling with drill string over 10,000m long has many technical challenges. Among them, the challenge to control the weight on bit (WOB) between a certain range is inevitable for the integrity of drill pipes and the efficiency of the drilling operation. Since WOB cannot be monitored directly during drilling, the tension at the top of the drill string is used as an indicator of the WOB. However, WOB and the surface measured tension are known to show different features. The deviation among the two is due to the dynamic longitudinal behavior of the drill string, which becomes stronger as the drill string gets longer and more elastic. One feature of the difference is related to the occurrence of high-frequency oscillation.
We have analyzed the longitudinal behavior of drill string with lumped-mass model and captured the descriptive behavior of such phenomena. However, such physics-based models are not sufficient for real-time operation. There are many unknown parameters that need to be tuned to fit the actual operating conditions. In addition, the huge and complex drilling system will have non-linear behavior, especially near the drilling annulus. These features will only be captured in the data obtained during operation.
The proposed hybrid model is a combination of physics-based models and data-driven models. The basic idea is to utilize data-driven techniques to integrate the obtained data during operation into the physics-based model. There are many options on how far we integrate the data-driven techniques to the physics-based model. For example, we have been successful in estimating the WOB from the surface measured tension and the displacement of the drill string top with only recurrent neural networks (RNNs), provided we have enough data of WOB. Lack of WOB measurement cannot be avoided, so the amount of data needs to be increased by utilizing results from physics-based numerical models. The aim of the research is to find a good combination of the two models. In this paper, we will discuss several hybrid model configurations and its performance.
Numerical Analysis of Second-Order Mean Wave Forces by a Stabilized Higher Order Boundary Element Method
Authors: Shao Yan-Lin 
Published: September 2018

A stabilized Higher-Order Boundary Element Method (HOBEM) based on cubic shape functions is presented to solve the linear wave-structure interaction with the presence of steady or slowly varying velocities. The m-terms which involves second derivatives of local steady flow are difficult to calculate accurately on structure surfaces with high curvatures. They are also not integrable at the sharp corners. A formulation of the Boundary Value Problem (BVP) in a body-fixed coordinate system is thus adopted, which avoids the calculation of the m-terms. The use of body-fixed coordinate system also avoid the inconsistency in the traditional perturbation method when 2nd order slowly-vary motions are larger than the linear motions.
The stabilized numerical method presented in this paper is based on streamline integration and biased differencing scheme along the streamlines. The presence of convective terms in the kinematic and dynamic free surface conditions will lead to instable solution if the explicit method is used. Thus a fully implicit scheme is used in this paper for the time integration of kinematic and dynamic free surface conditions. In an implicit scheme, solution of an additional matrix equation is normally required due to the fact that the presence of convective terms are approximated using the variables at current time step rather than the previous time steps only. A method that avoids solving such matrix equation is presented in this paper, which will reduce the computational efforts in the implicit method. The methodology is applicable on unstructured meshes. It can also be used in general second order wave-structure interaction analysis with presence of steady or slowly-varying velocities.
An Evaluation of Submarine Collisions to a TLP
Authors: Storheim Martin , Dørum Cato 
Published: September 2018

An engineering study was performed in 2017 to develop a multi-span suspension bridge on floating foundations across the Bjørnafjorden in Norway. The bridge was approximately five kilometers long and consisted of three main suspension spans supported by four pylons (towers). Two of the pylons were supported on tension-leg platforms (TLP) due to large water depths. The bridge has to be resistant towards collisions from passing ships. However, submarine impacts to the submerged parts of the bridge were also a challenge due to the bridge location being close to an active submarine training field.
This paper focus on the response of one such TLP towards collisions from submarines transiting below the bridge. Nonlinear explicit finite element analysis is used to study the possible collision scenarios, and the response of the TLP and the resulting bridge motion is evaluated. Further, transient failure of a tether was investigated to assess possible consequences of rupture of one of the tethers.