bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiphase Flow in a Subsea Hilly Terrain
Authors: Odan Mohamed , Ben Rajeb Faraj , Zhang Yan , Imtiaz Syed , Aborig Amer , Aziz Rahman Mohammed 
Published: September 2018

Multiphase flow is an important the phenomenon existing widely in nature, daily life, as well as petroleum and chemical engineering industry. It is especially important to understand the flow behavior of multiphase flow in a subsea hilly terrain and offshore pipelines. Accurate flow regime identification in multiphase flow is critical since multiphase flow affects the measurement accuracy of phase fraction, flow rate and other phase parameters.
The main objective of this research work is to obtain a better understanding of the multiphase flow characteristics in a long pipeline. In this study, the results of an experimental research on multiphase flow that investigates fluid characteristics in a pipe has been presented. The experimental unit consists of pipes that are made up of clear PVC, which is capable of producing several different flow regimes (Stratified, bubble, slug, and annular-mist flow) of gas-liquid flows. The entire length of the flow loop is 20.574 m. The experimental unit includes sensors such as pressure transducers, thermocouples and flowmeters that enable to measure the pressure ranges from 20–300KPa, temperature ranges from 0 to 20 °C and volume flow ranges from 12–45 liter/min at numerous locations respectively. In this experimental work, bubble, and slug flow regimes have been selected in the multiphase flow pattern to be examined on the multiphase flow assurance. The results of this research will provide valuable new experimental data on multiphase flow characteristics for designated flow regimes that can improve flow assurance in subsea conditions by including the temperature and Pressure effects.
Ice Propulsion Performance Calculation As per Alternative System of Propeller-Hull Interaction Coefficients
Authors: Kanevskii G. I. , Klubnichkin A. M. , Sazonov K. Ye. 
Published: September 2018

Propulsion performance of icebreakers cannot be calculated as per the classic system of propeller-hull interaction coefficients due to high negative values of wake fractions. To overcome this difficulty, this paper applies an alternative system of propeller-hull interaction coefficients. This system consists of thrust deduction fraction, coefficient of hull effect upon thrust and coefficient of hull effect upon torque.
The method suggested in this paper was used to analysis the data of ice trials for Vladivostok and Novorossiysk icebreakers. The input data in this analysis are speed in the ice field and required power. The sought values are propeller rotations per minute (RPM) and ice resistance. Propeller RPM values are compared versus the results of full-scale ice trials. Ice resistance values are compared versus the predictions based on the model test data obtained in ice basin of Krylov State Research Centre (KSRC).
It is shown that at low speeds in the ice field (0.5–5.0 knots), calculated propeller RPMs have good correlation with the full-scale measurement data.
This paper also gives propulsion performance calculation for Vladivostok icebreaker in 1.5-m thick ice field.
Numerical Simulation of a Pre-Swirl Stator Collision With Sea Ice Incorporating Various Material Model Based on Experimental Study
Authors: Ahn Jae-Woo , Choi Joong-Hyo , Park Sung-Gun , Han Sung-Kon 
Published: September 2018

The objective of this paper is to develop a realistic numerical model for ice–pre swirl stator (PSS) structure interaction problem under collision circumstance. PSS structure has been installed in front of a propeller of oil carrier or container vessel operating non-arctic region in order to increase efficiency of propulsion system, which was designed by Daewoo Shipbuilding and Marine Engineering (DSME). Recently, according to increase of port traffic in arctic region, it is being anticipated that market of PSS installed vessel operating in arctic region will be extended to pursue raised ship’s efficiency but in strength point of view, quantified assessment for dynamic interaction between PSS and sea ice is not specified in any design codes or classification rules. This standpoint will be led to an increased demand for the safe structural design of arctic vessel’s PSS structure subject to collision with sea ice.
In this study, DSME’s PSS structure design will be introduced and five types of numerical model to represent ice crushing behavior which were well-known though previous study will be investigated. The parameters of each material model of ice will be defined and more realistic numerical model for ice will be proposed through comparison study with experimental results. After that, the results of numerical simulations for a collision between PSS and sea ice with five numerical models using LS-DYNA software will be represented. In here, dynamic responses of PSS and failure behaviors of each ice model at each load case will be thoroughly evaluated. Collision loading scenarios and ice dimension were properly assumed based on polar class rule for propeller-sea ice interaction. Consequently, simplified analytic method and proper numerical model for ice corresponding to PSS-sea ice collision simulation will be proposed and discussed, respectively.
Hydrogen Induced Stress Cracking of Superduplex Steels: Effect of Operation Temperature
Authors: Haldorsen Lars M. , Nyhus Bård , Rørvik Gisle 
Published: September 2018

Duplex stainless steel has been used on subsea facilities since the mid 80-ties. The experiences with these materials have been relative good and only a few failures have been reported. However, BP and Shell experience some serious cracking of duplex steel in the mid 90-ties and in beginning of the century. The root cause of these failures was identified to be Hydrogen Induced Stress Cracking, HISC, where the hydrogen source was the cathodic protection system of the subsea facility. These and other similar failures resulted establishment of Joint Industry Projects, JIPs with financial and technical contribution from leading oil companies, contractors, material suppliers and research institutions as TWI, SINTEF and DNVGL. The objective of the JIPs was to establish practical usage limits for duplex stainless steels. The JIPs resulted in a recommended practice “DNV-RP-F112 - Design of duplex stainless subsea equipment exposed to cathodic protection.”
This document minimized the failure rate of duplex steel components used subsea. However, since duplex steels components have been used on subsea facilities long before the guidelines and recommendations were issued, there are lot of components presently in use that may be overloaded compared to guidelines and recommendations. As a part of life time extension of one of Statoil’s long time producing fields, a HISC re-calculation of spools connecting SPSs to infield pipelines showed that many of the spools were exposed to stresses above the recommended stresses given in DNV-RP-F112. Since these recommendations were primarily based on testing at ambient seabed temperature (4°C), Statoil, together with SINTEF, started in 2016 a project where the aim was to evaluate the resistance against HISC as an effect of the operation temperature.
The results of this project show that the critical net section stress/AYS (HISC resistance) increases with increasing temperature. Based on this, the before mentioned spools can be considered safe even though the spools are exposed to stresses above the recommendations in DNV-RP-F112.
Further, the investigations show that the guidelines and recommendations given in DNV-RP-F112 may be conservative for temperatures above 4°C. It is therefore recommended to perform more testing to confirm and incorporate the findings from the present investigation in future revision of DNV-RP-F112.
Experimental Investigation of Negative Damping Effects for a TLP Type Offshore Wind Turbine
Authors: Aoki Masaaki , Srinivasamurthy Sharath , Iijima Kazuhiro , Hara Naoyuki , Ikoma Tomoki , Nihei Yasunori 
Published: September 2018

Wind power generation has been paid much attention over the years as a countermeasure against global warming. Especially in recent years, researches and developments have also been made on Floating Offshore Wind Turbine (FOWT) in relatively deep offshore. Unlike Bottom-mounted Offshore Wind Turbine (BOWT), the motion characteristics of FOWT is complicated owing to coupled response of wind turbine and floating platform motions since the FOWT system is not fixed to the seabed. Due to these complexities, negative damping is one of the major problems reported for SPAR type FOWT moored by catenary chains. Negative Damping, in which the natural periodic motion is excited by blade pitch control employed for keeping the power generation constant, has to be addressed.
In this paper, we discuss the negative damping of TLP type FOWT with a series of dedicated experiments. We manufactured a 1/100th-scale model TLP type FOWT model with a primary control system of the blade pitch angle for a geometrically scaled model of the 5MW wind turbine based on the NREL. At first, we formulated the mechanism for occurrence of Negative Damping and derived the conditions under which unstable fluctuations of the floating platform occurs using the motion equation. After that, we conducted scale model tank tests in wind alone and confirmed the phenomenon wherein the fluctuation of the floating platform does not converge. Finally, how dangerous such coupled motion of wind turbine and floating platform would be for real-scale FOWT is discussed.
Modeling, Simulation and Validation of the Fluid Temperature of a Physical Drilling Simulator for Experimental Planning
Authors: Höhn Patrick , Aragall Roger , Koppe Michael , Oppelt Joachim 
Published: September 2018

Drilling equipment tests during field operations are always affected by uncertainties and variations regarding the local conditions in the borehole. In order to provide a more controlled testing environment for research, a hardware simulator was established at the Drilling Simulator Celle, Clausthal University of Technology. The simulator replicates the last 25 meters of a horizontal borehole and permits the drilling of a five-meter long rock sample. The setup includes a flow loop with two pumps for borehole cleaning and cuttings transport during the drilling process. During operation, temperature of the fluid increases due to pressure losses in the loop.
This paper introduces a basic model to determine the maximum allowable continuous operation time of the hardware setup. Further improvements can be achieved by doing sensitivity analyses of the parameters affecting the system behavior, e.g. ambient temperatures or mass flow rate. Measurements from the hardware setup are used for validation of the model and show consistent results.
Numerical Analysis of Wave and Current Interaction With Moored Floating Bodies Using Overset Method
Authors: Di Paolo Benedetto , Lara Javier L. , Barajas Gabriel , Paci Agnese , Losada Iñigo J. 
Published: September 2018

Numerical modelling of floating bodies is still being a very challenging issue, especially for large body displacements. Despite of the good performance of potential flow models in predicting floating body dynamics, there are still physical processes which are not well reproduced with that approximation. Their strong assumptions yield a lack of accuracy when high non-linear effects become predominant. In addition, the presence of restrictions to motion induced by mooring elements also introduces additional non-linear features which are sometimes out of the framework of the use of potential flow models. The use of CFD approach overcomes potential model limitations especially for non-linear effects. When CFD models are applied to solve waves and current interaction with floating bodies, several issues arise such as the numerical treatment of the floating element, mooring implementation and also the computational cost. Although several approaches are available in literature regarding the numerical implementation of floating bodies, the use of the Overset mesh appears as the more suitable one for large body displacement. Although accurate results have been obtained with re-meshing or even morphing techniques, large mesh deformation can yield into non-acceptable skewness and aspect ratio for the cells, consequently inducing numerical instabilities. In this work, we will present a numerical analysis of wave and current interaction with floating bodies. The objective of the work is to present a set of numerical implementations performed in OpenFOAM environment with the use of the Overset mesh method to study moored floating body dynamics due to the combined action of waves and current.
The implementations, included in IHFOAM (www.ihfoam.ihcantabria.com) are a new set of boundary conditions to generate waves and current without the use of relaxation zones. The main consequence is that the computational cost can be reduced due to the use of smaller domains. In addition, the implementation of mooring will be also presented in order to extend the use of the model to realistic conditions. Numerical model predictions compared with laboratory data of wave interaction with moored floating bodies have been performed showing a high degree of agreement. Comparison of floating body displacement and mooring tension will be presented. The combined effect of waves and current, traveling in the same and in opposite directions than waves, and their interaction with floating bodies and mooring will be also studied. Results will show the applicability of current method to model floating bodies.
Bubble Breakup and Coalescence Modelling for Subsea Gas Releases Using Computational Fluid Dynamics
Authors: Wu Kejia , Green Johnathan , Sivandran Subajan 
Published: September 2018

Bubble breakup and coalescence is a phenomenon which occurs within a developing subsea gas plume. A Computational Fluid Dynamics (CFD) model incorporating bubble breakup and coalescence was developed to describe the behaviour of a subsea gas release and the subsequent rising gas plume. The model was assessed for its suitability in capturing the characteristic behaviour of a rising gas plume by comparing the CFD results with experimental data obtained from underwater gas release experiments.
The study shows bubble breakup and coalescence plays a key role in determining the shape and the behaviour of a subsea gas release. Without the bubble breakup and coalescence included in the CFD model a narrower plume width and higher rising velocity is observed when compared to the experimental data. With bubble breakup and coalescence included the results obtained from the CFD model more accurately match the experimental data. Breakup and coalescence is a mechanism which redistributes the energy within the core of the gas plume towards the edge of the plume. This has a significant impact on the plume characteristics and is vital to be included in the CFD model to describe the behaviour of the released gas.
The study was carried out using air as the released gas. This was done to compare with the available experimental data where air was used as the source. However the CFD model developed is applicable for hydrocarbon subsea gas releases.
Experimental and Numerical Study of Vortex Induced Vibrations on a Spool Model
Authors: Gross David , Roux Yann , Rousse Benjamin , Pétrié François , Assier Ludovic , Minguez Matthieu 
Published: September 2018

The problem of Vortex-Induced Vibrations (VIV) on spool and jumper geometries is known to present several drawbacks when approached with conventional engineering tools used in the study of VIV on risers. Current recommended practices can lead to over-conservatism that the industry needs to quantify and minimize within notably cost reduction objectives.
Within this purpose, the paper will present a brief critical review of the Industry standards and more particularly focus on both experimental and Computational Fluid Dynamic (CFD) approaches. Both qualitative and quantitative comparisons between basin tests and CFD results for a 2D ‘M-shape’ spool model will be detailed. The results presented here are part of a larger experimental and numerical campaign which considered a number of current velocities, heading and geometry configurations. The vibratory response of the model will be investigated for one of the current velocities and compared with the results obtained through recommended practices (e.g. Shear7 and DNV guidelines).
The strategy used by the software K-FSI to solve the fluid-structure interaction (FSI) problem is a partitioned coupling solver between fluid solver (FINE™/Marine) and structural solvers (ARA).
FINE™/Marine solves the Reynolds-Averaged Navier-Stokes Equations in a conservative way via the finite volume method and can work on structured or unstructured meshes with arbitrary polyhedrons, while ARA is a nonlinear finite element solver with a large displacement formulation.
The experiments were conducted in the BGO FIRST facility located in La Seyne sur Mer, France. Particular attention was paid towards the model design, fabrication, instrumentation and characterization, to ensure an excellent agreement between the structural numerical model and the actual physical model. This included the use of a material with low structural damping, the performance of stiffness and decay tests in air and in still water, plus the rationalization of the instrumentation to be able to capture the response with the minimum flow perturbation or interaction due to instrumentation.
Research in Ballast Water Exchange for a Jack-Up Drilling Unit
Authors: Chunhui Li , Xuehui Zhang , Jianwei Xiao , Bo Zhou , Lei Cheng , Nan Zhao 
Published: September 2018

A new IMO Ballast Water Management Convention was adopted and came into force in 8th Sep. 2017. The IBWMC (International Ballast Water Convention) covered four major vessel types: Single/Double Hull Tanker, Bulk Carrier and Containership. Research in BWM (Ballast Water Management) of Jack-up Platform is rare.
The Jack up was built prior to the date which Convention comes into force and was delivered after date, so BWM of the Jack up is focused on Ballast Water Exchange Plan, which should be approved by Flag State or by CLASS (if authorized by Flag State). In this paper, a sequential method is hosen to exchange ballast water, and calculation is carried out to ensure that the stability is maintained in whole process.
Dynamic Cuttings Slip Velocity Evaluation in Non-Newtonian Fluids Using a Temperature Dependent Transient Drift-Flux Model for Directional Wells
Authors: Wiktorski Ekaterina , Sui Dan , Fjelde Kjell Kåre , Langåker Vebjørn 
Published: September 2018

The objective of drilling a well is to prepare a clean hole without obstructions for further casing and production tubing running. Cuttings transport has always been important, but challenging process, especially when drilling long directional wells. Poor hole cleaning causes severe problems, as stuck pipe, extreme torque and drag, difficulties in casing landing, cementing, etc. Extensive studies of cuttings transport, both theoretical and experimental, have been performed to estimate, for example, cuttings concentration and cuttings slip velocity to determine optimal conditions for effective hole cleaning.
This paper presents a dynamic analysis of cuttings transport in non-Newtonian fluids based on a transient drift-flux model and an associated numerical scheme AUSMV (advection upstream splitting method) developed by Evje and Fjelde 2002. In this paper, the scheme is modified to simulate cuttings transport dynamically taking into account effects related to pressure, temperature and cuttings slip.
During drilling, the heat is transported from the formation into the wellbore and up to the surface. In this paper, the energy balance is enhanced by introducing an analytical temperature model into the AUSMV scheme. The temperature distribution along the well is calculated at the beginning of simulation and kept constant throughout the simulation.
Additionally, the AUSMV scheme is improved by considering drilling fluid’s transport- and thermal properties. Transport properties of an oil-based mud, such as viscosity and density, are obtained from experiments. The experimental results were used to determine the coefficients in a linear density model used in the study to investigate the effect of non-Newtonian behavior on the heat transfer, cuttings transport and downhole pressure. Furthermore, a model to calculate the apparent viscosity at various pressures and temperatures was developed based on the experimental results and used to evaluate the impact of viscous forces on the cuttings distribution in the well.
Presented numerical scheme solves dynamic cuttings transport problems taking into account the slip velocity variation with wellbore geometry, operational (controllable) parameters and formation properties. In comparison to the traditional steady-state models, the transient cuttings transport model with integrated depth-dependent parameters gives a possibility to achieve a more realistic simulation of cuttings transport, distribution and accumulation along the wellbore through the time.
UHB Model Uncertainty for Structural Reliability Analysis of Pipeline OOS Design
Authors: Liu M. , Cross C. 
Published: September 2018

Design load factor structural reliability analysis is critical for pipeline postlay OOS design to mitigate global UHB for a trenched and buried subsea pipeline configuration operating at elevated temperature and pressure. During the detailed engineering phase it is necessary to evaluate and define any measure available to be finalised for UHB mitigation such as deep trenching selection, enhanced blanket or spot rockdumping. In order account for inherent uncertainties in the design variables, a pre-emptive SRA is normally performed for the probabilistic UHB design load factors prior to pipeline installation according to the typical trench imperfection statistics and some specified survey accuracy. As per the current practice the semi-analytical universal design curve method is used in the limit state for design load factor predictions. The SRA results will be updated once the OOS survey data become available. A rockdump schedule can then be established by FEA incorporating appropriate safety or load factors to address uncertainties in the design parameters and as-built pipeline OOS survey measurement accuracy.
This paper examines the UHB model uncertainties in the load factor and backfill cover assessment with a view to improving the SRA OOS analysis. Sources of uncertainties and variability in the UHB design are discussed first. Some disparity and inconsistency arising between the SRA and FEA models for the limit state are considered. Alternative UHB models are investigated by taking Timoshenko shear stiffness and associated deformation with pipe-soil interactions into consideration. A comparison is made with the conventional universal design curve method, the improved model and FE modelling to demonstrate the findings and conclusions. Of these, the pipe-soil interaction and its representation in the SRA limit state assessment are identified as a significant factor.