bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of a New, Correlated FEA Method of Assessing Mooring Chain Fatigue
Authors: Farrow Gary H. , Potts Andrew E. , Kilner Andrew A. , Kurts Phillip P. , Dimopoulos Simon , Jal Eric 
Published: November 2019

Abstract
The first phase of the Chain FEARS (Finite Element Analysis of Residual Strength) Joint Industry Project (JIP) aimed to develop guidance for the determination of a rational discard criteria for mooring chains subject to severe pitting corrosion which, based on current code requirements, would otherwise require immediate removal and replacement. Critical to the ability to evaluate the residual fatigue life of a degraded chain, is to have an accurate estimate of the chain in its as-new condition, thereby providing a benchmark for any loss in fatigue life associated with severe corrosion or wear.
A large collection of fatigue test data was collated for comparison and to establish underlying trends in as-new mooring chain fatigue response. A non-linear multi-axial Finite Element Analysis (FEA) fatigue assessment method was developed to correlate against available as-new chain link fatigue test data and underlying failure trends as part of the JIP achieving this critical requirement.
It was established that the linear FEA fatigue method currently employed in the industry is too simplistic and does not correlate with the fatigue test data, whereas an alternative method of assessing fatigue based on FEA, developed with respect to the DNV B1 material curve, correlates well with the available physical fatigue test data.
The FEA method uses a non-linear chain link FEA and multi-axial stress fatigue calculation method to determine an equivalent Stress Magnification Factor (SMF). This method achieves good correlation of predicted utilisations and associated cycles-to-failure with fatigue test data and in respect of critical locations with evidenced failure locations. The method of equivalent SMF calculation accounted for the significant effects on fatigue performance including proof load induced residual stress, mean stress levels and the increase in material fatigue endurance associated with increased steel UTS (i.e. increased offshore mooring chain grade). The analytical method developed in this study achieved a high degree of correlation with as-new chain fatigue test data, and should enable the accurate prediction of fatigue stresses around a link and in particular for irregular geometry associated with corrosion degraded chain links.
Simplified Numerical Simulation of the Dense Sand Progressive Failure Involved in Spudcan Punch-Through Failure
Authors: Zhao Jun , Sun Futai , Jin Wenbo 
Published: November 2019

Abstract
In the dense sand-over-clay strata, there is a potential for an installing spudcan to experience a sudden uncontrolled punch-through failure. Such a punch-through failure would seriously threaten safety of the rig structure, even cause casualties. To estimate the potential spudcan punch-through failure, this paper presents a simplified numerical method to calculate the full load-penetration resistance profile. The present approach allows the progressive failure of the overlying dense sand to be properly simulated by using an extended Mohr-Coulomb model. A series of large deformation finite-element (LDFE) analyses are carried out, varying the strength parameters. A fairly good performance of the present approach is verified by validating against groups of centrifuge tests data. Additionally, comparisons with the typical existing LDFE analyses in which both the simple and sophisticated constitutive models are conducted, show that the present approach performs fairly well to calculate the penetration resistance of a spudcan on dense sand overlying clay.
Enhancement of Structural Redundancy of Hull Structure in Accidental Condition by Applying Highly Ductile Steel
Authors: Nakayama Shin , Ueda Keiji , Aoki Masahiro , Matsumoto Kazuyuki 
Published: November 2019

Abstract
Application of steel plates with highly ductile is beneficial for ship owners, in order to improve structural redundancy and prevent environmental burden in accidental condition such as collision or grounding. Highly ductile steel, in which breaking strain is improved by 20% in comparison with conventional steels has developed, by optimizing microstructure. Excellent ductility was achieved selecting ferrite-perlite dual phase structure of ferrite phase which is advantageous for stable actual production. Morphology of ferrite phase control which consists of optimization of volume fraction and strengthening of ferrite phase itself by adding Si plays an important role to enhance ductility. The highly ductile steel of YP315 grade had acquired Class approval, and for ships to which high ductile steels are applied, ClassNK would assign the notation “Hull Protection by Highly Ductile Steel” (HP-HDS). MITSUBISHI SHIPBUILDING has evaluated the effect of highly ductile steel by numerical simulation for LPG (Liquefied Petroleum Gas) Carrier owned by Astomos Energy Corporation and Iino Kaiun Kaisha, Ltd. It has been confirmed that highly ductile steel can improve the structural redundancy by 20% in accidental condition by being applying to side structure.
A Research on Predicting Method of the Damage by Tsunami Drifting Objects in Urban Port
Authors: Masuda Koichi , Ikoma Tomoki , Aida Yasuhiro , Takada Masayuki , Fukunaga Yuta 
Published: November 2019

Abstract
When a tsunami arrives at an urban port, the most serious concern is the damage caused by tsunami drifting objects. In other words, the damage caused by tsunami drifting objects was also enormous, even in previous disasters. Containers, automobiles, timber, and other objects drifted, resulting in a blockade of the port of the harbor, which required a great deal of time and expense to restore. Therefore, estimating the scale and damage of the occurrence of drifting objects in harbors is extremely important in the early restoration and reconstruction of the port. Therefore, the purpose of the present paper is to develop a practical numerical simulator capable of quantitatively predicting the scale and damage of tsunami drifting at a port. In the present paper, we select containers as representative drift objects at ports and quantitatively predict the magnitude of drift damage by containers and other objects. According to the proposed simulator, prediction of the occurrence of the drifting of the container by the tsunami propagation calculation and the MPS method is predicted, and the subsequent drifting behavior of the container is predicted by the individual element method. The occurrence of tsunami drifting, drifting range, drifting speed, and collision force, etc., can be estimated by the proposed simulator. As an example, we present a case of drift damage prediction in the container yard of Shimizu Port in Shizuoka Prefecture.
Cement Plug Sealing Studies of Silica Cement Systems
Authors: Corina Anisa Noor , Opedal Nils van der Tuuk , Vrålstad Torbjørn , Sangesland Sigbjørn 
Published: November 2019

Abstract
A cement plug is widely applied for permanent abandonment phase to provide long-term zonal isolation against fluid flow. Maintaining cement plug integrity is a challenging task, and loss in cement sealing poses risks to the surrounding environment and surface safety. It is well-known that the cement performance is affected by cement material and downhole conditions. Nevertheless, investigations linking these influencing factors with the sealing of cement plugs are still limited, especially with the lack of proper equipment in the past.
In the present work, a small-scale laboratory setup has been constructed to test the sealing ability of a cement plug. It has unique features that can simulate plugging operations at the downhole conditions and preserve the cement curing condition. By testing using this setup, it is possible to measure the minimum differential pressure required for gas to flow across the cement plug and the gas leak rate. The silica cement mixture was selected as the plug material, prepared using silica flour. Investigation of silica cement under the influence of expanding agent additive and various curing temperature was carried out. It was found that adding an expanding agent improved the sealing of cement plugs. Moreover, samples cured at a high temperature were less resistant to gas flow with the leak path observed at the cement/steel interface, indicating debonding.
Optimization of Insulation and Heating System of Derrick for Arctic Mobile Offshore Drilling Unit
Authors: Liu Dahui , Wang Zhiyuan , Zheng Kaibo 
Published: November 2019

Abstract
The Arctic region contains abundant oil and gas resources. Due to the harsh environment of extremely low temperature and strong wind, it has a great impact on drilling activities. Therefore, it is necessary to carry out insulation measures for drilling equipment such as drilling derricks.
This paper analyzes the heat transfer mechanism of the derrick insulation wall of the drilling platform in the polar ice region. Based on the theory of computational fluid dynamics, the insulation materials of derrick on the polar drilling platform are investigated by numerical simulation. The number and position distribution of the heaters are selected, the effect of wind speed on insulation effect is explored, and the heating power of the derrick under the thermal insulation conditions is obtained. The simulated results are compared with those calculated by theoretical analysis.
The results show that in the polar environment, polyurethane can be used as the insulation material for the derrick of polar drilling platform. Five heaters can be arranged in the derrick, wherein three heaters are arranged on the bottom layer, and two heaters are arranged on the second floor of the derrick. When the heating time is short, the external wind speed has a relatively large influence on the temperature of the air inside the derrick, but when the heating time is long, the influence of the external wind speed is small. Under the thermal insulation conditions, according to the heat transfer equation and the heat balance theory, the required heating power is similar to the heating power obtained by the fluent software simulation.
Prediction of Hydrodynamic Damping of Moored Offshore Structures Using CFD
Authors: Jiang Changqing , el Moctar Ould , Schellin Thomas E. 
Published: November 2019

Abstract
Usually, mooring system restoring forces acting on floating offshore structures are obtained from a quasi-static mooring model alone or from a coupled analysis based on potential flow solvers that do not always consider nonlinear mooring-induced phenomena or fluid-structure interactions and the associated viscous damping effects. By assuming that only the mooring system influences the restoring force characteristics, the contribution of mooring-induced damping to total system damping is neglected. This paper presents a technique to predict hydrodynamic damping of moored structures based on coupling the dynamic mooring model with a Reynolds-averaged Navier-Stokes (RANS) equations solver. We obtained hydrodynamic damping coefficients using a least-square algorithm to fit the time trace of decay tests. We analyzed a moored offshore buoy and validated our predictions against experimental measurements. The mooring system consisted of three catenary chains. The analyzed response comprised the decaying oscillating buoy motions, the natural periods, and the associated linear and quadratic damping characteristics. Predicted motions, natural periods, and hydrodynamic damping generally well agreed to comparable experimental data.
In-Line VIV Based on Forced-Vibration Tests
Authors: Yin Decao , Wu Jie , Passano Elizabeth , Lie Halvor , Peek Ralf , Sequeiros Octavio E. , Ang Sze Yu , Bernardo Chiara A. , Atienza Meliza 
Published: November 2019

Abstract
Excitation and added mass functions determined from forced vibration tests of a rigid cylinder undergoing harmonic motion in the flow are used in the semi-empirical software VIVANA to predict the VIV response of pipelines.
An advantage of this approach, as opposed to the more-commonly-used response function approach, is that it can account for changing conditions along the length of the pipe, like changing current velocity, seabed proximity, and/or pipe diameter. This makes it useful for pipelines as well as for risers when such changes occur. Further, for pipelines, travelling wave effects play less of a role than for risers, so the VIVANA approach can be simplified by assuming the phase angle of the harmonic response is constant along the span.
The interactions between cross-flow and in-line response that complicate the prediction of cross-flow VIV by the excitation function approach, do not arise for pure inline VIV. For the latter case, using the pure in-line forced vibration test data of Aronsen (2007), it is found that both VIVANA approach and simplified ‘SIVANA’ approach thereof predict VIV amplitudes consistent with experiments on flexible pipe (Ormen Lange umbilical VIV tests), and the DNVGL-RP-F105 response function for a range of structural and soil damping values.
In a companion paper, this approach is applied partially strake-covered pipeline spans, to show that a relatively small fraction of well-placed strake coverage is enough to suppress in-line VIV.
Geometrical Optimization of U-Oscillating Water Columns in Random Waves
Authors: Scialò Andrea , Malara Giovanni , Arena Felice 
Published: November 2019

Abstract
This paper deals with the problem of designing an optimal U - Oscillating Water Column (U-OWC) device equipped with a Wells turbine. Specifically, the paper proposes the implementation of a genetic algorithm for designing a U-OWC exposed to the typical sea states available in the Mediterranean Sea. The first challenge encountered in this problem is the efficient calculation of the U-OWC hydrodynamic parameters. The second challenge relates to the fact that the U-OWC dynamics is governed by two coupled nonlinear ordinary differential equations with no closed-form solution. For reducing the computational cost, the genetic algorithm is combined with a semi-analytical approach used for determining the U-OWC hydrodynamic parameters and with a statistical linearization based approximate solution of the equations governing the U-OWC dynamics. Such a procedure allows estimating efficiently, albeit approximately, the power output of the system.
Numerical results compare a design based on a conventional “design sea state” vis-à-vis a design based on a “design wave climate”. For this purpose, the case study of the Roccella Jonica marina (Reggio Calabria, Italy) is considered, as relevant wave data are available to characterize the most energetic seas as well as depicting the global wave climate available at that location. The numerical results highlight the fact that an optimization conducted on the basis of a design sea state does not lead to an optimal design in a wave climate.
Experimental Analysis of Reduced-Scale Jumper for Deep-Sea Mining
Authors: Yamamoto Marcio , Fujiwara Tomo , Kanada Shigeo , Ono Masao , Takano Satoru , Yamamoto Joji 
Published: November 2019

Abstract
In the Deep-Sea Mining, the seafloor mining tool is connected to the subsea slurry pump by a piece of flexible pipe named jumper. The jumper’s shape is similar to a steep-wave flexible riser. Compared to a flexible riser, the jumper is a reinforced hose and has a shorter length. Numerous studies shed light on the dynamic behavior of flexible riser; however, all studies were carried out by the way of numerical analysis. We carried out, in the Deep-Sea Basin, an experiment using 1/5 reduced scale model of the jumper. Unhappily, the model’s bending stiffness had to be distorted. During the experiment, an oscillator generated harmonic motion on the top end of the model and a centrifugal pump circulated water throughout the model. In addition, we installed load cells on the top and bottom ends of the model. Our Basin is equipped with a visual measurement system. Thus, we measured the displacement of targets attached to the model. The initial results show that axial tension amplitude increases with the frequency of the top end oscillation. This response is due to the drag force on the lower bend increases with the frequency of top motion. We also could observe that the internal flow may increase the vertical motion amplitude. The jumper’s motion generates an oscillation on the internal differential pressure between both ends and the flow velocity. The differential pressure amplitude increases with the top oscillation frequency, but it is proportional to the top end oscillation amplitude. We will use these experimental results to validate our numerical models. Further, it is important to understand the internal flow effects to design the actual pump used to convey the slurry through the jumper.
Hydrate Remediation Philosophy for a New Flowline Intervention System Based on Active Heating
Authors: Guindeuil Geoffrey , Sanchis Arnaud , Harchambois Stephanie , Vivet Romain , Palermo Thierry , Pasquet François-Xavier , Tosi Guillaume 
Published: November 2019

Abstract
The Electrically Trace Heated Blanket (ETH-Blanket) is a new offshore intervention system currently in development by TechnipFMC for the efficient remediation of plugs due to hydrates or wax deposit in subsea production and injection flowlines. The ETH-Blanket consists of a network of heating cables placed underneath an insulation layer which is laid onto the seabed above the plugged flowline. By applying electrical power to the cables, heat is generated by Joule effect which warms up the flowline content until hydrate dissociation or wax plug remediation through softening or complete melting. The ETH-Blanket is currently developed within a Joint Industry project (JIP) between TechnipFMC and Total.
The dissociation of hydrate plugs using active heating incurs a number of risks for the integrity of the flowline and for the restoration of production to nominal conditions. As the flowline content is warmed up from ambient to hydrate dissociation temperature and during the dissociation of the hydrate plug, the pressure inside the flowline may potentially increase above design limits due to hydrate degassing and fluid volume expansion. Also, plug run-away scenarios may occur if a large pressure difference exists between both sides of the plug. The remediation operation may fail because of insufficient power or misplacement of the ETH-Blanket. Lastly, even following successful operation of the ETH Blanket, new flowline blockage may occur during subsequent operations such as cold re-start.
To mitigate those risks, a hydrate remediation philosophy has been developed specifically for the ETH-Blanket Service. It is based on the development of in-house tools and procedures and builds upon experimental and modelling work performed as part of a previous JIP focusing on the dissociation of hydrate plugs using an ETH-Pipe-in-Pipe [1]. This paper introduces the different elements of the hydrate remediation philosophy, including the development and experimental validation of the dedicated tools used to define the appropriate heating sequence for the safe and efficient dissociation of hydrate plugs.
Predicting Extreme Waves From Wave Spectral Properties Using Machine Learning
Authors: Gramstad Odin , Bitner-Gregersen Elzbieta 
Published: November 2019

Abstract
An important question in the context of rogue waves is whether the statistical properties of individual waves, and in particular the probability of extreme and rogue waves, can be linked to the properties of the underlying wave spectrum of the relevant sea state.
It has been suggested that a narrow wave spectrum (in frequency or direction) combined with a large wave steepness may lead to increased occurrence of extreme waves. Parameters based on the ratio of the wave steepness to the spectral band-widths have therefore been suggested as indicators of increased probability of extreme waves. However, for realistic ocean conditions the success of such parameters seems to be questionable.
In this paper, we investigate relations between short-time wave statistics and wave spectral properties by using machine learning methods that can take a much wider range of spectral properties, or even the entire directional wave spectrum, into account. Numerical simulations with a nonlinear wave model that provides phase-resolved wave information are combined with wave spectra from a spectral wave model. Machine learning methods are then employed to investigate how well the wave statistics can be predicted from knowledge about the wave spectrum.
The results are discussed in the context of existing parameters suggested as indicators of rogue waves, as well as with respect to potential warning against sea states in which extreme waves are expected to occur, based on wave-forecast from spectral wave models.
Numerical Investigation of Scour Around Subsea Pipelines Near the Seabed
Authors: Yin Guang , Cheng Zhen , Liu Shengnan , Ong Muk Chen 
Published: November 2019

Abstract
In the present study, two-phase flow simulations using SedFoam (an open-source multi-dimensional Eulerian two-phase solver based on OpenFOAM) are employed to investigate the scour phenomenon around pipelines in the vicinity of the seabed. A complete transport profile from the immobile bed, to slowly moving quasi-static bed and upper transport layers can be captured by the present model. The fluid Reynolds stress is modeled using the two-phase k-ε model. The particle stresses due to binary collisions and enduring contacts are modeled by kinetic theory for granular flow and a phenomenological frictional model, respectively. The model is first validated through a two-dimensional (2D) simulation of scour around a single pipeline near the seabed. The predicted time-dependent scour profiles as well as the scour depth are compared with the simulation results of Lee et al. (2016) and the experimental data reported by Mao (1986). A numerical experiment is then carried out to investigate the scour around the piggyback near the seabed. The effects of different locations of the small pipeline on the scour depth are studied.