bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimation of Welding-Induced Plastic Zone Size and Residual Stress Levels: Linear Heat Input Approximation
Authors: Bhardwaj Sachin , Ratnayake R. M. Chandima 
Published: October 2021

Abstract
Welding is a highly nonlinear temperature distribution process, where the presence of high-temperature gradients leads to the development of significantly high residual stress levels, up to and/or beyond the material yield strength magnitude and localized plastic deformation. To achieve the desired dimensional accuracy, determination of plastic zone size, shape, and location is critically important in reducing or controlling final distortions, decreasing the residual stress according to length scale, and defining the optimum sequence of the welding process. The plastic zone caused by welding has been found to be directly proportional to linear heat input, defined in (J/mm). The use of actual linear heat input in the estimation of welding-induced residual stress in finite element models often results in an overestimation of heat transferred to the fusion zone of the metal. This manuscript highlights the importance of estimating plastic zone, developed during thermal processes like welding, and its role in mitigating final distortion by using a 3-bar model for the determination of final residual stresses. In the second part, previously developed analytical linear heat input solution for 2D residual stress models is discussed and further demonstrated using examples from open literature. Lastly, a sequentially uncoupled thermal and thermo-mechanical finite element analysis (FEA) is performed, using a generalized plane strain element, and concluded by validation of the numerically developed plastic zone size with analytically developed solutions.
Multiphase Flow Induced Vibrations at High Pressure: CFD Analysis of Multiphase Forces
Authors: Emmerson Paul , Lewis Mike , Barton Neil , Orre Steinar , Lunde Knud , Klinkenberg Arnout , Macchion Olivier , Challabotla Niranjan Reddy , Belfroid Stefan 
Published: October 2021

Abstract
CFD analysis of a high pressure 2” pipe test loop with water-gas flow was undertaken using three different solvers. Multiphase flow induced forces were predicted on the bends at a range of operating pressures between 10 and 80 barg and compared with forces reconstructed from vibration measurements.
Overall the three different CFD solvers predicted consistent results. The fluid forces predicted on the bends of the double U-loop test rig have a good range of values compared to the test reconstructed forces. The forces predicted at low pressure were in line with the experimental reconstructed values, whilst at high pressure all three CFD solvers predicted higher forces. The trend of the forces reducing with increased operating pressure, evident in test, was matched by one of the CFD methods, but less well by the other two. At low operating pressure the forces are dominated by the momentum of the liquid in the multiphase flow, whilst at high pressure the pressure fluctuations and turbulent effects will be more important. All three CFD solvers use VOF methods and above about 40 barg it is possible that they struggle to fully resolve the flow behaviour, which will be more influenced by bubble and droplet entrainment and turbulence.
Multiphase flow can induce high amplitude vibrations in piping systems, potentially leading to fatigue failures. CFD modelling offers a potentially powerful tool to provide the flow induced forces required for assessing and diagnosing multiphase flow induced pipework vibration problems in hydrocarbon production systems.
Hydrodynamic Impact on Wedges During Water Entry
Authors: de Oliveira Costa Daniel , Sena Sales Junior Joel , Fernandes Antonio Carlos , Corrêa Rodrigo dos Santos 
Published: October 2021

Abstract
The problem of water entry of wedges represents one of the most classic research topics in fluid mechanics. Along the past decades, many different analytical methods have been proposed to calculate pressure distribution and peak loads during the water entry, such as Wagner (1932) and Dobrovol’skaya (1969). Zhao and Faltinsen (1993) and Mei (1995) present numerical solutions based on potential theory assumptions (inviscid, irrotational and incompressible flow). For more complex geometries and cases these methods might not be accurate enough due to the simplifications assumed, and in these cases the use of computational fluid dynamics (CFD) might be an interest tool to provide more accurate analysis.
This work presents CFD results for different conditions of water entry of 2D wedges. The simulations were performed with a marine dedicated flow solver, FINE™/Marine from NUMECA, which features an unsteady Reynolds-averaged Navier-Stokes (URANS) solver and a finite volume method to perform spatial discretization. The multiphase flow is represented through the Volume of Fluid (VOF) method for incompressible and nonmiscible fluids. Different water entry conditions are explored. The effect of the mesh size, time step and other setup parameters over the results are discussed for simulations with 2D wedges to extend to other studies of water impact. The wedge velocity and hydrodynamic pressure distribution along the model’s face are monitored during the water entry and compared to experimental data from previous publication (Yettou et al, 2006) for water entry of wedges during free fall.
Experimental Investigation of the Coupling Between Aero- and Hydrodynamical Loads On A 12 MW Semi-Submersible Floating Wind Turbine
Authors: Thys Maxime , Souza Carlos , Sauder Thomas , Fonseca Nuno , Berthelsen Petter Andreas , Engebretsen Espen , Haslum Herbjørn 
Published: October 2021

Abstract
Model tests were performed with a model of the INO WINDMOOR 12 MW floating wind turbine in the Ocean Basin at SINTEF Ocean. The tests were done at a scale of 1:40. RealTime Hybrid Model testing was used for the modelling of the wind turbine rotor and aerodynamic loads. A subset of the results is analysed to study the influence of the wind on the platform motions, the acceleration at tower top, the loads at base of tower and the relative wave elevation. The study is based on the comparison of the quantities of interest for different tests with the same moderate sea-state but with different wind modelling: no wind, constant thrust force, turbulent wind of 11.5 m/s and turbulent wind of 25 m/s.
The wind modelling has a minimal influence on the platform surge and pitch response in the wave-frequency range. On the other hand, the aerodynamic loads, including wind turbine controller dynamics and turbulent wind, has an important impact on the low-frequency surge and pitch response.
The aerodynamic loads are important for the loads at tower base due to the dominance of the tower-RNA induced gravitational loads at low-frequency.
Maximum relative wave elevation was found to be mainly dependent on the thrust induced mean pitch angle.
A Numerical Investigation on Hydrodynamic Interaction Coefficients for a Group of Truncated Composite Cylinders Floating in Waves
Authors: Ali Mir Tareque 
Published: October 2021

Abstract
When a group of bodies are floating closely in waves, the fluid loading on these bodies will be influenced due to the presence of the neighboring bodies. The wave loading on each of these bodies are affected, because of the sheltering or wave-reflection effects due to the presence of surrounding floating bodies, while additional loads are exerted by the radiated waves produced by the motions of the nearby floating bodies. For a multiple floating body system, it is important to precisely compute the hydrodynamic interaction coefficients, since these parameters will be used later to solve the 6xN simultaneous equations to predict the motion responses (where N is the number of freely floating bodies in the multi-body system). On the other hand, the hydrodynamic interaction coefficients are absent for an isolated floating body case. This paper investigates the hydrodynamic interaction coefficients for a group of three dimensional (3-D) bodies floating freely in each other’s vicinity. Since the nature of hydrodynamic interaction is rather complex, it is usually recommended to study this complicated phenomenon using numerically accurate scheme. A computer code developed using 3-D source distribution method which is based on linear three-dimensional potential theory is used and the validation of the computer code has been justified by comparing the present results with that of the published ones for the hydrodynamic interaction coefficients of multiple bodies. The agreement between the calculated results with those of the published ones is quite satisfactory. Numerical simulations are further conducted for a group of identical truncated composite circular cylinders floating vertically at close proximity in regular waves. During the computations of hydrodynamic interaction coefficients of this multi-body model for different groups, the number of members in the group as well as the gap width among them has been varied. The paper also examines the occurrence of hydrodynamic resonances in the gap among the floating bodies and the presence of spikes with rapid fluctuation in the results of the diagonal and coupling terms for interaction coefficients. Finally, some conclusions are drawn on the basis of the present analysis.
An Experimental Investigation of Nonlinear Wave Generation by Flap Wavemakers
Authors: Fouques Sébastien , Laflèche Sébastien , Akselsen Andreas , Sauder Thomas 
Published: October 2021

Abstract
It is well known that flap wavemakers behave in a nonlinear way when either the flap angle or the flap velocity becomes large. Moreover, the hinge depth should be adapted to the period of the generated waves in order to minimize linear evanescent modes, which may contribute to the formation of nonlinear spurious waves. For example, imposing a sinusoidal motion with a relatively long period and a large amplitude to a short flap will result in a surface elevation composed of a regular wave with the same period as the flap motion, but also of a variety of harmonics with higher frequencies. Second-order harmonics can be predicted theoretically for regular and irregular waves, and they can be corrected by modifying the control signal of the wavemaker. However, there is no theory that can describe nor mitigate effects of orders higher than two. The design of the wavemaker is then essential to generate extreme sea states with good quality and predictability in a laboratory.
In this paper, the nonlinearities of flap wavemakers are investigated experimentally for regular and irregular waves generated in SINTEF Ocean’s laboratories. Nonlinearities of order two and three are estimated from times series of the surface elevation measured at different locations by an array of wave probes. Particular focus is put on identifying the effects of the classical second-order correction on the second- and third-order harmonics.
An Adaptive Method to Further Improve the Tolerance of an ANN-Based Detection System for Mooring Line Failure
Authors: Sidarta Djoni E. , Tcherniguin Nicolas , Lim Ho-Joon , Bouchard Philippe , Kang Mengchen , Leridon Aurelien 
Published: October 2021

Abstract
The use of an Artificial Neural Network (ANN) for detection of mooring line failure has been a growing subject of discussion over the past several years. Sidarta et al. [6, 8, 12] have presented papers on the detection of mooring line failure of a moored vessel by monitoring shifts in the low frequency periods, mean yaw angles as a function of vessel positions, mass and added mass.
An ANN model has been trained using MLTSIM hydrodynamic simulations based on information from the early stages of the project. The restoring forces and moments from mooring lines, risers and umbilicals have been solved using catenary equations to significantly reduce the computational time to generate the ANN training data. This paper presents the evaluation of this ANN model using fully coupled OrcaFlex hydrodynamic simulations, based on the latest information of the project. The results of this evaluation demonstrate the tolerance of the trained ANN model as it can properly function when tested using time series of vessel motions from the fully coupled OrcaFlex hydrodynamic simulations. Furthermore, although the ANN model has been trained using simulations with a completely removed line, the trained model can still function when tested with simulations of a line broken at the bottom. These give affirmation that the ANN model can tolerate the differences that exist between the test and training data.
Sensitivity of the polyester line stiffness has also been performed using fully coupled OrcaFlex hydrodynamic simulations, and the computed time series of vessel motions have been used to test the ANN model. The ANN model can deal with some level of differences between the sensitivity tests and training data. However, sensitivity tests of the polyester line stiffness to model aging lines has posed a real challenge to the ANN model as its prediction accuracy has decreased significantly. This paper presents an adaptive method that can be implemented such that the ANN model can adapt to relatively new conditions that are quite different from the training data and maintain the accuracy of its prediction. With this approach, an existing ANN model that has been trained under certain assumptions of the system can still function although the behavior of the system has drifted away from those assumptions.
This phenomenon may have similarity with a possible reality that measured behavior in the field can be somewhat different from numerical simulations. This adaptive method has a potential for addressing this issue such that a simulation trained ANN model can maintain its expected accuracy although dealing with different conditions from the training data. If successful, this is a good cost saving scenario that an ANN model adapts to some degree to relatively new and different conditions before the differences become too much to handle and the only solution is to retrain the model.
Load Coefficients and Dimensions of Raschel Knitted Netting Materials in Fish Farms
Authors: Moe Føre Heidi , Endresen Per Christian , Bjelland Hans V. 
Published: October 2021

Abstract
New types of fish farms are often larger and structurally more complex than conventional fish farming structures, and associated challenges concerning safety and costs increase correspondingly. Thus, increased precision in structural design is required, with estimation of hydrodynamic loads on nets as an important topic. Today, both load coefficients for nets and measured netting dimensions are given with relatively high uncertainties. New knowledge for netting materials with high solidities as well as scaled netting commonly applied in model tests are included in the presented study. Results from towing tests and the development of a new mathematical expression for local drag coefficients (for netting twines) indicate that drag coefficients are not only dependent on solidity and Reynolds number, but may also be affected by the velocity reduction and the local velocity at the twines.
Ground Effect on Current Energy Harvesting From a Freely-Oscillating Circular Cylinder at Low Reynolds Number
Authors: Hamada Ahmed A. , Fürth Mirjam 
Published: October 2021

Abstract
This paper investigates the potential of current energy harvesting from a freely-oscillating circular cylinder, with a focus on near-ground effects. Energy can be harvested by converting the oscillatory motion of a cylinder excited by water current into electricity. The boundary shear layer, created by the ground surface, interacts with the cylinder vortices and consequently affects the force behavior and power harvesting performance. The problem is simulated in a two-dimensional turbulent flow, using the Finite Volume (FV) solver and the dynamic motion module, inherited in OpenFOAM. Ground effects on the power generation capacity of an oscillating cylinder operating in river current velocity at Reynolds number of 3 × 104 are studied at varying depths. Vortex-induced vibration is studied to observe the ground boundary layer influence on the structural response, vortex structure, hydrodynamic forces, and gained power. The results shed physical insight into the understanding of the flow behavior of the oscillating cylinder near the ground. Simulations show that the ground effect appears when the distance between the cylinder and the ground is less than three times the cylinder’s diameter. Decreasing the gap distance between the cylinder and the ground suppresses the vortices behind the oscillating cylinder, causing an increase in the harvested energy. Further, the optimal-power harvesting distance between the ground and the freely-oscillating cylinder is two and half times the cylinder’s diameter, because of the high oscillating frequency, causing higher power relative to shorter distances.
IOR/EOR Methods Adapted to High Water Production Zones of Heavy and Extra-Heavy Oil Reservoirs in La Faja Petrolifera Del Orinoco-Venezuela: State of the Art
Authors: Rodriguez M. Fernancelys 
Published: October 2021

Abstract
Venezuela is well known for its immense reserves of heavy and extra heavy crude oils located in La Faja Petrolífera Del Orinoco (La FPO), in the east of the country, with certified reserves of up to 235 billion barrels. The main production methods that have been applied in La FPO are Cold Production with sand through vertical and horizontal wells, and the application of Thermal IOR/EOR methods (e.g. steam injection, In-situ Combustion, SAGD, etc.) and Chemical EOR methods (e.g. polymer flooding).
One of the main challenges in La FPO is the increase in the recovery factor (with &lt; 10% of recovery factor to date), due to the low mobility of crude oil at reservoir conditions, and the presence of local and regional bodies of water (flushed zones and aquifers) where conventional cold production methods are not efficient. The presence of these bodies of water negatively affects the production profiles and the quality of crude oil, observing high water cuts due to the adverse mobility ratio and the formation of complex emulsions that affect the crude lifting and separation systems.
Due to the current dramatic decline in production of conventional reservoirs in Venezuela and the vital role of La FPO to support Venezuelan oil production, it is important to identify methods and new technologies that allow for the increase in recovery factors in these complex reservoirs. This paper presents a literature review of the applied production methods and those that could be envisaged, including horizontal and dewatering wells as well as reported research work (e.g. Chemical EOR methods), to increase the oil recovery in flushed zones and/or reservoir zones with high water cuts in La FPO.
Application of Fracture Mechanics to Structural Fatigue Assessment Based on Spectral Method
Authors: Samaria Sagar , Kyoung Johyun , O’Donnell Jeffrey , Zhang Bob 
Published: October 2021

Abstract
The spectral fatigue methodology is a widely accepted methodology to compute the fatigue life of an offshore platform. The ever-increasing demand for life extension of the existing floating platforms worldwide continues to grow. ABS Guide for Fatigue Assessment of Offshore Structures and DNVGL-RP-C203 have established guidelines for employing finite element analysis (FEA) to calculate fatigue lives using the spectral fatigue method.
For complex structural details, the FE models with 2-D elements may not be able to capture the actual geometric details accurately. Hence, detailed FE models with solid (3-D) elements are utilized to capture geometric SCF’s (stress concentration factors) for these locations. The fatigue lives thus obtained using SCF approach with 2-D elements can be highly conservative or inaccurate. To overcome unreliable fatigue results for such complex locations that need using 3-D elements for a better definition of the local structure, this paper presents an extension to the defined guidelines by employing spectral fatigue methodology to 3-D solid elements. The paper also illustrates the applicability of Engineering Criticality Assessment (ECA) using stress-histogram based Fracture Mechanics Evaluation (FME) approach.
A comparative study is performed for a critical weld location on an offshore platform using solid 3-D and shell 2-D FE models. First, FEA is performed for both the models to calculate fatigue lives using the S-N curve-based approach. In addition, FME is also performed for the same critical weld location in order to provide a more accurate and reliable solution that will enable clients to plan their in-service inspections and maintenance programs. Also, presented is a comparison of fatigue lives based on the solid and shell element FME.
Estimation of Cuttings Concentration and Frictional Pressure Losses During Drilling Using Data-Driven Models
Authors: Ozbayoglu Murat , Ozbayoglu Evren , Ozdilli Baris Guney , Erge Oney 
Published: October 2021

Abstract
Drilling practice has been evolving parallel to the developments in the oil and gas industry. Current supply and demand for oil and gas dictate search for hydrocarbons either at much deeper and hard-to-reach fields, or at unconventional fields, both requiring extended reach wells, long horizontal sections, and 3D complex trajectories. Cuttings transport is one of the most challenging problems while drilling such wells, especially at mid-range inclinations. For many years, numerous studies have been conducted to address modeling of cuttings transport, estimation of the concentration of cuttings as well as pressure losses inside the wellbores, considering various drilling variables having influence on the process. However, such attempts, either mechanistic or empirical, have many limitations due to various simplifications and assumptions made during the development stage. Fluid thixotropy, temperature variations in the wellbore, uncertainty in pipe eccentricity as well as chaotic motion of cuttings due to pipe rotation, imperfections in the wellbore walls, variations in the size and shape of the cuttings, presence of tool joints on the drillstring, etc. causes the modeling of the problem extremely difficult. Due to the complexity of the process, the estimations are usually not very accurate, or not reliable. In this study, data-driven models are used to address the estimation of cuttings concentration and frictional loss estimation in a well during drilling operations, instead of using mechanistic or empirical methods. The selected models include Artificial Neural Networks, Random Forest, and AdaBoost. The training of the models is determined using the experimental data regarding cuttings transport tests collected in the last 40 years at The University of Tulsa – Drilling Research Projects, which includes a wide range of wellbore and pipe sizes, inclinations, ROPs, pipe rotation speeds, flow rates, fluid and cuttings properties. The evaluation of the models is conducted using Root Mean Square Error, R-Squared Values, and P-Value. As the inputs of the data-driven models, independent drilling variables are directly used. Also, as a second approach, dimensionless groups are developed based on these independent drilling variables, and these dimensionless groups are used as the inputs of the models. Moreover, performance of the data-driven model results are compared with the results of a conventional mechanistic model. It is observed that in many cases, data-driven models perform significantly better than the mechanistic model, which provides a very promising direction to consider for real time drilling optimization and automation. It is also concluded that using the independent drilling variables directly as the model inputs provided more accurate results when compared with dimensional groups are used as the model inputs.