bluuebunny/crossref_metadata_2025_split huggingface dataset:
Three-Dimensional Numerical Analysis of Horizontal and Vertical Coalescence of Bubbles at Two Submerged Horizontal Orifices on the Wall
Authors: Li Z. P. , Sun L. Q. , Yao X. L. , Piao Y. 
Published: November 2019

Abstract
In the process of bubbling from two submerged adjacent orifices, bubbles coalescence becomes inevitable. But the study of the evolution and interaction of bubbles from submerged orifices is little, especially numerical simulation. In this paper, combined with mesh smoothing technique, mesh subdivision technique and the technique of axisymmetric coalescence and 3D coalescence, a three-dimensional model of bubbles coalescence at two submerged adjacent orifices on the wall is established by the boundary element method. Then, numerical simulations were carried out for horizontal and vertical coalescence before detachment. Finally, by changing the ventilation rate and the Froude number, the effects of different ventilation rates and buoyancy on the process of bubbles coalescence at two adjacent orifices were investigated. The results show that for horizontal coalescence, the effect of ventilation rate is more pronounced than buoyancy. As the ventilation rate increases or the influence of buoyancy is decreased, the amplitude of internal pressure fluctuation of the bubble decreases and the coalescence time decreases. For vertical coalescence, the effect of buoyancy is more pronounced than ventilation rate. With the influence of buoyancy is decreased, the vertical coalescence time is increased, the internal pressure of the bubble is decreased. The influence of ventilation rate is similar to that of horizontal coalescence.
Analysing Dependent Failures in a Bayesian Belief Network
Authors: Fam Mei Ling , Konovessis Dimitrios , He Xuhong , Ong Lin Seng , Tan Hoon Kiang 
Published: November 2019

Abstract
Fault trees (FT) and event trees (ET) have been used thoroughly in risk analysis and there have been a few published articles outlining how to map FTs and ETs to Bayesian Belief Networks (BBN). There have been documented benefits of a BBN being able to consider Common Cause Failures (CCF) and conditional dependencies. With modelling CCFs in a BBN, there is a possibility to increase the level of analysis of a CCF by breaking down the analysis to the respective CCF Categories, such as Environment, Maintenance or Design. This allows a better understanding of the contributing events given a defined accident scenario. Also, in the decommissioning industry, there is no established database yet for CCF of components, as decommissioning projects are sparse and spread out across different operating conditions. Hence it may be practical to adjust generic CCFs to obtain facility-specific parameters for common cause failures. The paper thus highlights how to express CCFs with a Beta-Factor Model in a BBN and by extension, undertake an extended level of analysis according to CCF categories and adjust generic database common cause factors to a facility-specific factor based on a checklist. The technique is applied to a risk analysis of a well plugging and abandonment event.
Wave Response of a Novel Breakwater Concept With Oscillating Water Columns
Authors: Han Mengmeng , Wang Chien Ming , Duan Wenhui 
Published: November 2019

Abstract
A novel concept of a mega floating breakwater-windbreak is proposed for reducing both wave height and wind speed on its leeward side. L-shaped internal channels are installed inside the breakwater hull that surface from the floating breakwater as tubes that function like “trees” to break the wind. The channel openings are on the vertical walls at the upstream side of the breakwater, so that water is allowed to oscillate inside the channels and create extra viscous damping. Numerical studies using both linear boundary element method and CFD were carried out to determine the wave transmissibility and wave force on the breakwater with and without the internal channels. The wave condition in the Gold Coast, Australia was selected as an environmental input. Operating wave condition and extreme wave condition were separately investigated. Scaled dimensions were used to study the breakwater behavior in a wave flume. The results show that when water oscillates inside the channels, the transmitted wave height and lateral wave force acting on the breakwater will be reduced. In addition, since the viscous effect influences waves of all lengths, the internal channels improves the breakwater performance in blocking long waves.
Fundamental Study on Development on Numerical Method for Evaluation of Wave Power Generating Systems With Pendulum Type by the Particle Method
Authors: Murata Kazuki , Rheem Chang-kyu , Ikoma Tomoki 
Published: November 2019

Abstract
In this paper, we report the proposal and development of the numerical model. The model applies to two and three dimensional problems. We introduce the model to the MPS method which is a kind of particle method, and discuss applicability of the model on numerical test of aerial physical pendulum in free torque load; the present model was compared with the theoretical solution by the 4th order Runge-Kutta method. As a result, we confirmed the good reproducibility of the model. And we can say that the model is suitable for analyzing the problem of physical pendulum.
Secondary, we examine the practicability of this model in the regular wave from the calculation results. The tests are examined by a two-dimensional problem in order to reduce calculation cost. In addition, we conducted fluid-structure interaction analysis using the present model and confirmed the applicability of its model to fluid field analysis.
Research on the Improved Body-Force Method Based on Viscous Flow
Authors: Li Zhiheng , Yu Jiawei , Feng Dakui , Jiang Kaijun , Zhou Yujie 
Published: November 2019

Abstract
The virtual propeller model can achieve the rapid numerical prediction of the ship self-propulsion performance through viscous flow, which used the improved body-force method. The two-dimensional lift coefficient CL and the drag coefficient CD are very important parameters in this method, which are generally obtained by the potential flow methods and cannot incorporate viscous effects. This study will perform a fully nonlinear unsteady RANS (Reynolds Average Navier-Stokes) simulation to get the KP505 open-water characteristics and then divide its blade into several parts to get the lift coefficient CL and the drag coefficient CD on each one. Then fitting by multivariate regression method, the relationship between CL, CD and propeller parameters is obtained. The Unsteady Blade Element Theory (UBET) is coupled with RANS in house CFD code HUST-Ship (Hydrodynamic Unsteady Simulation Technology for Ship) to calculate the flow around the propeller. RANS equations are solved by the finite difference method and PISO arithmetic. have been made using structured grid with overset technology. The results show that comparing with the EFD data, the maximum differences of the result of the improved body-force method are 4.32% and 2.7% for the thrust coefficient and the torque coefficient respectively near the propeller operating point.
Numerical Simulations of OC3 Spar and OC4 Semi-Submersible Type Platforms Under Extreme Conditions in the East Sea, Korea
Authors: Shin Hyunkyoung , Yu Youngjae , Pham Thanh Dam , Kim Junbae , Kumar Rupesh 
Published: November 2019

Abstract
Since the Paris Conference of the parties in 2015, interest in renewable energy around the world is higher than ever. Korea also has plans to increase the proportion of renewable energy to 20% by 2030 through the renewable energy 3020 policy. Of these, 16.5GW is filled with wind power, the installation area is expanding from land to sea. Among them, some of big plans are using floating offshore wind turbines based on the marine environments in Korea. In this study, numerical simulations of the NREL 5MW wind turbine were performed using NREL FAST V.8. A comparison was made between two types of floaters, spar and semi-submersible, installed 58km off the Ulsan Coast with 150m water depth in the East Sea, Korea. The environmental data were obtained from the Meteorological Administration’s measured data and NASA’s reanalysis data, MERRA-2. Design Load Cases were selected by referring to IEC 61400-3. Maximum moments at both blade root and tower base, six-degrees of freedom motions and three mooring line tensions were compared.
Computational Fatigue Assessment of Chains Working in Twisted Conditions
Authors: Martinez Perez Imanol , Gabrielsen Øystein 
Published: November 2019

Abstract
Chains are extensively used in the Oil and Gas industry for mooring vessels or floating platforms, both for temporary and long-term moorings. Moreover, recently they found a new application in the mooring of floating wind turbines. The integrity of mooring systems is of great importance for both industries. Failure Records [1]–[2] indicate that fatigue of mooring chains is one of the main causes of failure, and therefore their lifetime prediction represents an important challenge for industry. Chains are intended to work under Tension Loading, however, anomalous loading modes such as Out-of-Plane Bending (OPB) or Twisting can appear. For example, OPB caught the attention of engineers after the Girassol incident; where it was identified as the main cause of failure of several chain links eight months after the installation [3]. Since this failure, OPB has attracted the attention of several research programs and multiple publications can be found in the literature (For example, [4]–[5]). Twist may occur during the installation of a chain or during service due to torque generated in the near-by elements of the mooring (for example wire cables). This paper presents a computational fatigue assessment of mooring chains working in twisted conditions. It is based on a two steps analysis: a mechanical and a fatigue analysis. The mechanical analysis accounts for the initial residual stress state of the chain after manufacturing and subsequent proof loading. The result is the stabilized cycle of the multiaxial stress field, which is obtained through an elastic-plastic three-dimensional Finite Element Analysis (FEA). Then, the fatigue analysis is performed to predict the failure location and determine the lifetime. The predicted failure location has shown good agreement with fatigue cracks found in recovered chain links in the North Sea after more than 15 years of service.
The Influence of Tidal Unsteadiness on a Tidal Turbine Blade Flow-Induced Vibration
Authors: Arini Nu Rhahida , Turnock Stephen R. , Tan Mingyi 
Published: November 2019

Abstract
The influence of unsteady tidal flow on the flow-induced vibration of a vertical axis tidal turbine blade is investigated numerically in this paper. A 2D CFD model is developed to simulate the blade flow-induced vibration in OpenFoam. The vibration is caused by dynamic loading from the unsteady tide. It is recognized that the unsteady tidal current mainly comes from the changes in tidal velocity magnitude and angle of attack experienced by a tidal turbine blade as it rotates. This paper studies numerically how velocity magnitude and initial angle of attack influence tidal turbine blade vibrations and the effects of the velocity and angle of attack are evaluated separately where the unsteadiness parameters are varied around a set of environmental condition. The vibration is examined through time histories of blade displacement, pressure distribution on the blade surface and the tidal current regime. The blade is assumed to have pitch and heave responses thus the vibration is in the form of transverse and torsional vibrations. The results show that increasing tidal velocity magnitude strengthens the torsional vibration. The increase of angle of attack is likely to generate chaotic motions and enhance both transverse and torsional vibrations.
Numerical Study of a Single-Point Mooring Gravity Fish Cage With Different Deformation-Suppression Methods
Authors: Cheng Hui , Aarsæther Karl Gunnar , Li Lin , Ong Muk Chen 
Published: November 2019

Abstract
Compared to the multi-point mooring fish cage, the single point mooring (SPM) fish cage can spread out the accumulation of organic matter to prevent the local environment from being overwhelmed, and reduce the manufacturing cost at the same time. Thus, it has attracted many attentions recently. In this research, different deformation-suppression methods are applied to the SPM system with a typical Norwegian fish cage aiming to reduce the cultivation volume loss. A well-validated software, FhSim, is used to conduct the full-scale numerical study. The effects of the three deformation-suppression methods (i.e. (i) adding the lower bridles, (ii) adding the frontal rigid frame, (iii) adding the trawl door) are analyzed under pure current and combined wave-current conditions. The results indicate that all the three methods can reduce the cultivation volume loss at least by 32% compared to the one with the original SPM system when the current velocity is larger than 0.5 m/s. In addition, moving the conjunction point close to the bottom ring can bring positive effect in the cultivation volume maintaining with an unnoticeable increase in the tension force. This study will provide practical advice and useful guides for the SPM fish cage design.
The Impact of Modelling Air Compressibility in the Selection of Optimal OWC Design Parameters in Site Specific Wave Conditions
Authors: Simonetti Irene , Cappietti Lorenzo 
Published: November 2019

Abstract
The importance of properly modelling the effects of air compressibility in the selection of the optimal design parameters for an Oscillating Water Column wave energy converter is investigated. For this purpose, a wide dataset of capture width ratios, obtained from both experimental tests and Computational Fluid Dynamic simulations, is used to formulate an empirical model able to predict the performance of the device as a function of its basic design parameters (chamber width and draught, turbine damping) and of the wave conditions (wave period, wave height). A multiple non-linear regression approach is used to determine the model numerical coefficients. The data used to formulate the model include the effects of air compressibility. The impact of considering such effects on the selection of the optimal geometry of the device is evaluated and discussed by means of the model application for the optimization of a device to be installed in a site located in the Mediterranean Sea (in front of the coast of Tuscany, Italy).
World First Fatigue S-N Curve for Bonded Reinforcements for FPSO Application
Authors: Abbad El Andaloussi Hamza , Mouton Luc , Sayed Ahmad Firas , Mahérault-Mougin Stéphanie , Paboeuf Stéphane , Errotabehere Xabier 
Published: November 2019

Abstract
Steel is the most common construction material in the Oil & Gas industry, and it begins to rust the day it is cast. This observation raises several challenges for the asset integrity and life extension of all offshore units. Therefore, for the ageing FPSOs (&gt;10 years), frequent and costly structural maintenance operations in hazardous environment may be required to repair their hull. While a standard ship can go to dry-dock for “crop and renew” maintenance operations through standard hot works techniques, a permanently moored asset has to be maintained in situ. The challenge is to perform these offshore structural maintenance operations with no production disruption while maximizing safety even for the most stressed areas such as a mid-ship deck plating.
COLDSHIELD, a co-development between COLD PAD, TOTAL and IFP Energies nouvelles, has been set up to meet this very challenge. This innovative alternative to “crop and renew” is covered by approval certificate from Class. COLDSHIELD stops the corrosion and restores hull structural strength. Two industrial applications have been performed so far. Among the steps to be taken to demonstrate that such repair can be considered as permanent, it was mandatory to characterize the fatigue behavior of this reinforcement solution.
While the fatigue behavior of steel has been an important research topic since the early eighties of the last century, its understanding for bonded composite materials is still at its infancy. Indeed, for the time being there is — to our knowledge — no S-N curve for structural bonded reinforcements. Full scale coupon specimen fatigue tests of the structural bonded reinforcements were conducted by COLD PAD, third-partied by Bureau Veritas and in collaboration with two laboratories (private and public) in order to study the adhesive fatigue. A statistical analysis was performed according to international standards. The resulting S-N curve is fit for industrial fatigue design. It demonstrates a comfortable fatigue strength (S-N curve presenting a slope of 9).
This paper presents the results of a fatigue life assessment campaign of COLDSHIELD including the experimental setup, the fatigue test results, and the numerical analyses. It details the reason why the design is compatible with a stress-based approach. It also explains the conclusions that can be derived in terms of fatigue life for a deck repair campaign.
Efficacy of Analysis Techniques in Assessing Broken Wave Loading on a Cylinder Upon a Shoal
Authors: Dassanayake Darshana T. , Antonini Alessandro , Raby Alison 
Published: November 2019

Abstract
Estimation of impulsive wave loading on a cylinder upon a shoal, such as an offshore rock lighthouse constructed on a partially emerged offshore rock with a steep foreshore, poses a unique challenge to marine structural engineers. Large and small scale experimental investigations are the most feasible methods to study this phenomena. However, any experimental investigation with impulsive loading faces challenges in the data analysis, when it is necessary to separate the total impact forces from the force response time series, and to separate the impulsive and quasi-static force components of the total force measurements. This paper is an attempt to re-visit several data analysis techniques with a unique experimental data set to study the advantages and limitations of those techniques, and also to learn how different techniques can be combined into a data analysis methodology to harness maximum information.
Assessment of Variations in the Physico-Mechanical Properties of Fiberglass Tubing Working in Different Environments
Authors: Diniţă Alin , Minescu Mihail , Dumitrescu Andrei , Teodoriu Cătălin , Săraru Codruţ Ştefan 
Published: November 2019

Abstract
This paper presents the results of the experimental investigations carried out by the authors in order to evaluate the changes in the physico-mechanical properties of fiberglass tubing used to transport fluids between different facilities. In the near future, water injection wells will be equipped with fiberglass tubing, as an alternative to the more traditional metal tubing. The mechanical properties of fiberglass material (ultimate tensile strength, impact energy, burst pressure) have been determined for sets of 5 specimens that have been maintained (at a temperature of 80°C) in different environments and with different exposure times (hydrochloric acid: 6/24/48 hours; acetic acid: 6/24/48 hours; hydrochloric acid + hydrofluoric acid: 6/24/48 hours; xylene: 1/2/3 months; condensates: 1/2/3 months).
Numerical Modeling of Radial Fracturing of Cement Sheath Caused by Pressure Tests
Authors: Gheibi Sohrab , Sangesland Sigbjørn , Vrålstad Torbjørn 
Published: November 2019

Abstract
To achieve an acceptable level of zonal isolation, well integrity should be guaranteed in hydrocarbon production and geological CO2 sequestration. Well pressure test can cause different types of failures in the well system leading to leakages through these failures. Laboratory evidences have revealed that occurrence of radial tensile fractures is likely during pressure tests.
In this paper, we use a numerical code call MDEM which was formulated based on discrete element method. The code can model discontinuum feature of fractures. A model of a lab-sized pressure test was built and compared to an experiment previously published. The model was tested under different confinement levels and effect of the tensile strength of rock on the radial fracture was investigated at the same lab-scale. Fracture opening profiles are also presented showing the leakage potential of these fractures under different pressure level.
How Does a Stationary Sand Bed Affect the Flow Dynamics in an Eccentric Annulus?
Authors: Bizhani Majid , Kuru Ergun 
Published: November 2019

Abstract
In the drilling operations, it is common to have a stationary bed of the drilled cuttings in the high angle sections of the wellbore. The bed must be removed in the later stages before running the casing, or when it starts to cause high torque and drag on the drill string. The mere act of circulating drilling fluid, however, may not clean the well (i.e., critical flow rate and shear stress for bed erosion must be reached). In an effort to better understand the underlying mechanisms of bed removal process during hole cleaning, in this paper, we look at how the presence of a stationary sand bed affects the flow field in an eccentric annulus.
Experiments simulating turbulent flow of water in an eccentric annulus with/without the presence of stationary sand bed have been conducted by using a 9m long horizontal flow loop (with an annular configuration of 95 mm ID outer pipe and 38 mm OD inner pipe). The flow loop was equipped with particle image velocimetry (PIV) system, which was used to collect velocity field data. The PIV data were then used to study the characteristics of the turbulent flow of water in the eccentric annulus. The velocity field and Reynolds stress profiles were analyzed in two planes, one perpendicular to the bed interface and off-center of the annulus, and the other along the center-line of the annulus. Experiments were carried out with the presence of two different height stationary sand beds and also without a sand bed as the control case.
The extent to which the presence of the sand bed affects the flow appears to be a strong function of the bed height in the annulus. For a small bed height, deviation of the velocity field from the no bed case was slight. In this case, Reynolds normal and shear stress values were lower near the bed interface comparing to the annulus centerline.
On the other hand, for a flow over a thicker bed, this behavior changed, and the flow became more uniform in the annulus (in terms of turbulence and mean flow properties). The results help in understanding the mechanism of bed erosion under constant pump flow rate. From the practical point of view, data presented here suggest that hole cleaning in an eccentric annulus progressively becomes more difficult as the bed becomes smaller. The results also explain why in long horizontal and extended reach wells often wiper trips are required for proper cleaning of the hole.