bluuebunny/crossref_metadata_2025_split huggingface dataset:
Surveillance Models of Large-Scale ESP With High Viscosity Fluids and Gas
Authors: Barrios Lissett , Scott Stuart , Deuel Charles 
Published: August 2013

The paper reports on developmental research on the effects of viscosity and two phases, liquid–gas fluids on ESPs which are multi stage centrifugal pumps for deep bore holes.
Multiphase viscous performance in a full-scale Electrical Submersible Pump (ESP) system at Shell’s Gasmer facility has been studied experimentally and theoretically. The main objectives is to predict the operational conditions that cause degradations for high viscosity fluids when operating in high Gas Liquid Radio (GLR) wells to support operation in Shell major Projects. The system studied was a 1025 series tandem WJE 1000.
The test was performed using this configuration with ten or more pump stages moving fluids with viscosity from 2 to 200 cP at various speed, intake pressure and Gas Void Fractions (GVF). For safety considerations the injected gas was restricted to nitrogen or air.
The ESP system is a central artificial lift method commonly used for medium to high flow rate wells. Multiphase flow and viscous fluids causes problems in pump applications. Viscous fluids and free gas inside an ESP can cause head degradation and gas locking. Substantial attempts have been made to model centrifugal pump performance under gas-liquid viscous applications, however due to the complexity this is still a uncertain problem. The determination of the two-phase flow performance in these harmful conditions in the ESP is fundamental aspects in the surveillance operation.
The testing at Shell’s Gasmer facility revealed that the ESP system performed as theoretical over the range of single flowrates and light viscosity oils up to Gas Volume Fractions (GVF) around 25%. The developed correlations predict GVF at the pump intake based on the operational parameters. ESP performance degrades at viscosity higher than 100cp as compared to light oil applications, gas lock condition is observed at gas fraction higher than 45%. Pump flowrate can be obtained from electrical current and boost for all range of GVF and speed.
The main technical contributions are the analysis of pump head degradation under two important variables, high viscosity and two-phase flow inside the ESP.
Finite Element Analysis of Nonlinear Water Wave-Body Interaction: Computational Issues
Authors: Vendhan C. P. , Sunny Kumar P. , Krishnankutty P. 
Published: August 2013

Design of floating structures exposed to water waves often requires nonlinear analysis because of high wave steepness and large body motion. In this context, Mixed Eulerian-Lagrangian (MEL) methods for nonlinear water wave problems based on the potential flow theory have been studied extensively. Here, the Laplace equation with Dirichlet boundary condition on the free surface is solved using the boundary integral method, and a time integration method is used to find the particle displacements and velocity potential on the free surface. Finite element methods based on the MEL formulation have been developed in the 90s. Several researchers have pursued this approach, addressing the various challenges thrown open, such as velocity computation, pressure computation on moving surfaces, remeshing of the computational domain, smoothing and imposition of radiation condition. Apart from these, the implementation of the FE model in particular involves several computational issues such as element property computation, solution of large banded matrix equations, and efficient organization of computer storage, all of which are crucial for the computational tool to become successful. A study of these aspects constitutes the primary focus of the present work.
The authors have recently developed a 3-D FE model employing the MEL formulation, which has been applied to predict waves in a flume and basin. The fluid domain is discretized using 20-node hexahedral elements. The free surface equations are solved in the time domain employing the three-point Adams-Bashforth method. Validation of the numerical model and relative computation times for salient steps in the FE model are discussed in the paper.
Hydroelastic Response of a Ship Structural Detail to Seakeeping Loads Using a Top-Down Scheme
Authors: Sireta François-Xavier , Derbanne Quentin , Bigot Fabien , Malenica Šime , Baudin Eric 
Published: August 2013

In order to investigate the local response of a ship structure, it is necessary to transfer the seakeeping loading to a 3DFEM model of the structure. A common approach is to transfer the seakeeping loads calculated by a BEM method to the FEM model. Following the need to take into account the dynamic response of the ship to the wave excitation, some methods based on a modal approach have been recently developed that include the dry structural modes in the hydro-structure coupling procedure and allow to compute the springing and whipping response of the ship structure to the seakeeping loads.
In the context of the fatigue life assessment of a structural detail, a very fine FE model is required. A very large number of seakeeping loading cases also need to be considered to account for all the conditions encountered by the ship through its life. It becomes then clear that because of the CPU time issue, the whole FE model can not be very fine. This is why a hierarchical top-down analysis procedure is commonly used, in which the global ship structure is modelled in a coarse manner using one finite element between web frames. The structural details are modelled separately using a fine meshing. Such top-down methods are commonly used for the estimation of the quasi-static response of structural details to the seakeeping loads.
This paper presents a methodology in which a top-down method is used to estimate the springing response of a ship structural detail loaded with wave pressure, and its fatigue life. The global dry structural modes are transferred to the detail fine model using the shape functions of the finite elements of the global model. The hydrodynamic pressures are computed directly on the fine mesh model, avoiding any interpolation error. The imposed displacements at the fine mesh boundary are computed using the same method that is used to transfer the structural mode shapes, and the local pressure induced loads and inertia loads are applied on the fine mesh nodes.
This method is applied for the calculation of the elongation of a strain gauge which is installed in the passage way of an ultra large container ship.
Study of the Reliability of the Ship Transportation by Applying the Historical Hindcast Weather Data
Authors: Kauczynski Wojciech E. 
Published: August 2013

Regularity of ship transportation depends strongly on environmental conditions, on the ship’s route and on the seakeeping characteristics of a vessel. The ship’s route property selected and the ship characteristics designed appropriately to a region of the ship operation can assure a higher regularity of the transportation.
In the presented paper an exemplifying analysis of the ship transportation on a selected typical ship’s route has been performed. The principal purpose of such an analysis was to determine the magnitude and distribution of speed losses in a realistic operational environment to serve as a basis for estimation of reliability of the sea transportation.
The aim of the analysis precludes the use of long term statistics as this would not give a correct representation of the extreme value tail of the probability distribution of sailing time. Instead of this, the ship performances on the considered sea routes were simulated in roundabout trips by applying time series of historical (hindcast) weather data (waves, swell, wind, and ocean current). The applied data cover three complete years starting from February 2003 and they are specified with the 6 hour time interval at about 3000 grid points covering almost the whole world ocean area.
Two vessels which represent typical classes of ships (a tanker and a container ship) were used in this analysis. The ships voyages were simulated with different departure time and with the time interval of 6 hours providing high sailing frequency and the considerable large amount of results. Results of the calculations were analyzed with respect to the seasonal variations, alternative routes, and different power settings. The purpose of these numerical exercises was to illustrate how to perform the analysis and to present a scope of the obtained results.
A Small-Scale Field Experiment on Random Froude-Krylov Force on a Rectangular Structure
Authors: Arena Felice , Malara Giovanni 
Published: August 2013

This paper investigates random Froude-Krylov (FK) force on a rectangular structure. It is a key parameter in the design process of some maritime structures. Indeed, the exciting force on a large floating body is commonly determined by a contribution due to the incident wave field (FK) and by a contribution due to the diffraction of sea waves.
The work is based on results of a small-scale field experiment at NOEL (Natural Ocean Engineering Laboratory) in Reggio Calabria, Italy. First, field experiment is described, with characteristics of the selected sea states. Then, FK forces are analytically derived in the context of linear random waves. Frequency spectrum of the FK force is derived and it is discussed the occurrence of zeros in frequency domain.
Extreme FK forces are determined by Quasi-Determinism theory. The theory enables to derive the analytical expression of the FK force when a large wave (either a large crest height or a large crest-to-trough wave height) occurs at any given point of the wave field, in a fixed time instant. Time domain representation allows investigating the wave force and extreme wave pressure. It is shown that the wave force is highly width dependent in time domain. Further, time histories are not quasi-impulsive. This characteristic is well-rendered in large structures (large with respect to the dominant wave length), where the wave group crossing gives rise to a time history “protraction” in time domain.
In the last part of the paper theoretical results are supplemented by comparison with experimental data.
The Wake Flow Behind Azimuthing Thrusters: Measurements in Open Water, Under a Plate and Under a Barge
Authors: Cozijn J. L. , Hallmann R. 
Published: August 2013

The wake flow behind a ducted azimuthing thruster was investigated. The thruster wake is an important factor in thruster interaction effects. Model tests were carried out for 3 different configurations; a thruster in open water conditions, a thruster under a flat plate and a thruster built into a barge. Two different thrusters were considered, a ‘normal’ thruster with a horizontal propeller axis and a ‘tilted’ thruster with a propeller axis and nozzle oriented 7 deg down-wards. In the tests the propeller thrust and torque were recorded, as well as the nozzle thrust and unit thrust. The velocities in the wake of the thruster were measured using a PIV (particle image velocimetry) system, for down-stream locations up to x/D = 19. The influence of the thruster tilt, the plate above the thruster and bilge radius on the thruster wake flow were investigated.
Detailed PIV measurements were carried out on the wake flow behind the thruster in open water conditions. The PIV system used can measure 3D velocities in large set of points in a 2D plane, which is illuminated by a laser light beam. The flow velocities were measured in a large number of cross sections at different distances from the thruster. The PIV measurements provide a detailed image of the flow velocities in the thruster wake, showing the axial velocities, as well as the rotation and divergence of the wake.
Subsequently, PIV measurements were carried out for the thruster under a flat plate and the thruster under a barge. The measurement results show a thruster wake that is deformed by the presence of the plate and the barge. The plate and the bottom of the barge form a flat plane above the thruster, clearly flattening the cross section of the thruster wake. Furthermore, the wake flow at the side of the barge, near the bilge radius, results in a low pressure region, causing the wake flow to diverge up as it flows from under the barge into the open water. This phenomenon is known as the Coanda effect and is strongly dependent on the bilge radius and the distance between the thruster and the side of the barge. The effect of both these parameters was confirmed in the model test results presented. The typical flow patterns observed as a result of the Coanda effect are illustrated in Figure 1 below.
The results of the present model test research are used to further improve the understanding of the physics of thruster interaction effects. Furthermore, the results will serve as validation material for CFD calculations.
Response-Based Analysis of FPSO Systems for Squall Loadings
Authors: Minnebo Joerik , Izadparast Amir H. , Duggal Arun , Huijsmans René H. M. 
Published: August 2013

Squalls can be the major design driver for FPSO systems in offshore West Africa where other environmental loadings are relatively benign. The measured squall time series indicate a transient change in the wind speed, starting with a sudden increase to a peak wind speed followed by a rapid decay, all within a total duration of about an hour. In the design of FPSOs for squall loadings, careful attention needs to be given to the transient characteristics of squalls.
The main objective of this investigation is to characterize the response of FPSO systems subjected to squalls and develop a robust approach for estimating the design value. For this purpose, first, the dynamic behavior of an FPSO in squalls is studied and then the significant squall parameters that affect the dynamic response of the FPSO are identified. The results of this study are utilized to define the upper bound of the dynamic amplification factor and the upper limit of the extreme response of the FPSO. Next, three different response-based approaches: a) based on the long-term statistical analysis of the response, b) based on the long-term statistical analysis of the squall parameters and c) based upon the dynamic amplification limitations, are utilized to estimate the design values. Finally, the design value estimates obtained from the response-based approaches are compared with those estimated from scaling squall time traces to the 100-year peak wind speed. The study is mainly focused on spread moored systems; however, the proposed methods are also tested on turret moored FPSOs, and their application for these dynamically complicated systems is evaluated.
Fatigue Life Improvement of Welded Doubling Plates
Authors: Lotsberg Inge , Fjeldstad Arne , Helsem Morten Ro , Oma Narve 
Published: August 2013

Fatigue life assessment is important for all floating offshore structures related to the new building stage but also related to lifetime extensions. Fatigue cracking occurs normally due to uncertainties in estimated fatigue life and this is a well-known problem for floaters.
In this paper the aim has been to look deeper into the effects of improvement methods for improvement of the fatigue life of structural connections.
Fatigue testing of full size fillet welded doubling plates has been performed of a specimen in as welded condition for comparison with two specimens improved by grinding. The paper also presents an alternative S-N curve for grinded details.
The primary goal is to assess the possibility for fatigue life improvement of fillet welded doubling plates where fatigue cracking may initiate from the weld root. The information gained in this project is considered to be important for the offshore floater industry, as well as for development of new fatigue assessment procedures and requirements in standardization.
Verification of Fracture and Fatigue Performance of Titanium Gr. 29 Welds in Tapered Stress Joints
Authors: Buitrago Jaime , Nissley Nathan A. , Rombado Gabriel 
Published: August 2013

Design of a Steel Catenary Riser (SCR) requires the use of connection hardware to accommodate the bending moment that arises from the abrupt change in stiffness at the floater hang-off. Reliability of this connection hardware is of paramount importance in ultra deepwater applications (up to 3000m), especially those involving high pressure and temperature fluids. One type of such connection hardware is a metallic tapered stress joint. Because of its inherent density, strength, and stiffness, steel is not well suited for these applications due to the length and weight constraints. Titanium Gr. 29 (Ti), which is as strong as steel but lighter and more flexible, has been identified as a good material candidate for a tapered stress joint.
The required length (∼40ft) and thickness (∼3.5in.) of the Titanium Stress Joint (TSJ) cannot be fabricated as a single piece due to forging size limitations. Thus, an intermediate girth weld becomes necessary. The fracture and fatigue performances in the presence of the external seawater and cathodic protection (CP) and the internal sour production with galvanic effects between the Ti and steel must be assessed to verify the service life of the stress joint. ExxonMobil has developed and initiated a Joint Industry Project to fully address the fracture and fatigue qualification of titanium welds. In particular, the project plans to establish a robust methodology for the future qualification of TSJs that parallels, to the extent possible, the qualification process currently used for SCRs.
This paper discusses the primary aspects of the titanium weld qualification: (1) selection of test specimens, (2) load frequency effects on initiation and propagation lives, (3) environmental assisted cracking due to hydride formation under cathodic and galvanic conditions, (4) full-thickness small-scale fatigue, (5) size effect on fatigue, and (6) weld inspection.
A New Design for Floating Offshore Platforms
Authors: Khonsari S. V. , England G. L. , Moradkhan E. , Valikhani A. R. , Bahadori M. R. 
Published: August 2013

While for shallow waters the use of old offshore jackets still seems efficient and justifiable, for deep and ultra-deep waters such platforms cannot be used. During the past few decades the old generation of fixed offshore platforms was succeeded by the new floating platforms and new designs such as FPSOs.
A new family of floating offshore platforms has been developed. These should be able to respond to size, weight and space for operating equipment, i.e. they can be constructed to have a wide range of load-bearing capacities. Use is made of the old concept of Life Saving Tubes, which in their simplest form can be a toroidal shaped tyre inner tube. The Torus-shaped idea can be further extended to other shapes obtained either by revolving any plane closed curve or poly-line about a coplanar axis which does not intersect it, or by extruding the curve/poly-line through a closed path.
The preliminary ‘structural’ calculations carried out on various samples of the torus-shaped members of this family of platforms showed that theoretically they can be designed to carry as much load as required and provide the users with the required space on the water. Moreover, basic studies of the stability of such systems in water showed their large metacentric heights as well as large righting moment arms, hence their high degree of stability. This stability can be further increased by using other versions of this idea with more efficient toroidal shapes. Furthermore, apparently, much study is required however to establish this idea as a viable, cost-effective and efficient alternative for current generations of offshore floating platforms.
Development of a New Underwater Piling Noise Mitigation System: Using Hydro Sound Dampers (HSD)
Authors: Kuhn Christian , Bruns Benedikt , Fischer Jan , Gattermann Jörg , Elmer Karl-Heinz 
Published: August 2013

The aim of the recently published climate control by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMU) is a reduction of the German greenhouse gas emissions down to 20 % in 2050, compared to the generated greenhouse gas in 1990. To reach the given target a huge growth in renewable energy is necessary. One of the most potential possibilities to produce renewable energy in Germany will be the installation of offshore wind turbines.
During the installation of offshore wind foundations such as monopiles, tripods, tripiles and jackets, mostly large tubular steel piles are impact driven to final penetration depth. In the process of impact driving, considerable underwater sound emissions will appear. In recent times, peak sound pressure levels above 190 dB re 1 μPa have been measured at a distance of 750 m away from the installation ground. These peak sound pressure levels, produced during the installation of any kind of driven offshore foundation, is potentially harmful to marine life, in particular to marine mammals such as harbor porpoises, harbor seals or grey seals.
To protect the marine life the German Federal Maritime and Hydrographic Agency (BSH) set the maximum allowed underwater sound pressure level to 160 dB (SEL) at a distance of 750 m away from pile driving.
To reach the given target by the BSH a new underwater piling noise mitigation system using so called hydro sound dampers (HSD) is presently developed at the Institute for Soil Mechanics and Foundation Engineering at the Technische Universität in Braunschweig (IGB-TUBS). After small scale tests in the so called ‘large wave channel’ in Hannover a full scale test was performed in the Baltic-Sea some weeks ago.
The results of the measurements are very promising, as a reduction of 12 up to 20 dB could be generated. Besides existing noise mitigation systems one of the main advantage of the hydro sound dampers is, that the mitigation can be pre-adjusted to a predefined frequency range, as marine mammals are sensitive only for a certain sound frequency range.
In this paper, the results of the small and large scale tests and some new research findings concerning the shape and the material of the hydro sound dampers will be presented.
Optimization of FPSO’s Main Dimensions Using Genetic Algorithm
Authors: Mazerski Grzegorz 
Published: August 2013

An efficient concept design of FPSO is supported by a wide variety of tools and methods. Some use parametric solutions for a variety of projects, while others deal with project-specific issues.
One of the early challenges is to establish main dimensions of the “buoyancy element” for Floating Production System. The size should provide appropriate load-carrying capacity at minimum cost within limits of a given field development project. Since the financial implications of the hull size are significant, the choice should be made by means of a proper engineering study. One of the most promising approaches to this task is to utilize Multi Objective Genetic Algorithm (MOGA) for optimization of main particulars.
A method was developed that aims at finding optimum main dimensions of the FPSO unit of given storage capacity with respect to steel weight and strength. This was achieved by utilizing MOGA optimization tool available in NAPA stability software package. The paper presents procedures, challenges and samples of results of such studies. The method was recently utilized in two different FPSO concept projects. First comments and conclusions that were drawn from the results of the procedure will be presented. Some ideas for future development will also be given.