bluuebunny/crossref_metadata_2025_split huggingface dataset:
Viscous Damping of Floating Bodies in Waves
Authors: Graham J. Michael R. , Downie Martin J. 
Published: October 2015

A numerical method developed from earlier work [1, 2] of predicting damping due to eddy shedding from sharp or rounded bilges of a hull of arbitrary cross-section in beam waves is presented. The method matches an inner solution which simulates the local bilge section separated flow numerically to an outer wave potential flow solution. The latter can be any standard 3-dimensional panel or other method for the whole body which provides the local values of the matching velocity parameter at all bilge sections which shed eddies. Scaling by the matching parameter provides a physically based sectional damping coefficient for a response computation. In the case of free response of a floating body feed-back from the viscous damping to the bilge velocity parameter through the response mode amplitudes necessitates iteration which generally converges very quickly.
Computational predictions carried out in the frequency domain using this prediction method assuming linear wave theory for the outer flow are presented and compared with laboratory wave tank measurements for roll response of two floating hulls in regular and random waves. Application of the method to viscous damping of more complex geometries is also possible.
Steel Steep Wave Riser as an Alternative Configuration for FPSO’s Compliant Risers
Authors: Pereira Paulo S. D. , Mourelle Marcio M. , de Aguiar Ludimar L. 
Published: October 2015

The work was focused in the chase for alternative configurations that could resist to the high FPSO motions in the Brasil’s Pre-Salt harsh wave environment, and that could also be less compliant laterally when compared to the SLWR solution.
A case study was taken where an infield 8 inch SLWR configuration has been taken for comparisons.
After adjusting the SSWR (Steel Steep Wave Riser) main characteristics such as top angle, buoyant section length, buoyancy modules geometry and spacing, feasible configurations have been obtained. For a configuration to be considered as feasible, a set of verifications have been carried out including extreme events, wave fatigue, vortex induced vibration and installation. The verification was performed considering several riser top connection positions and azimuths along the FPSO riser support balcony.
The interference with neighboring risers has been also taken as an important issue, but was taken solely for comparison with the SLWR configurations.
The installation phase has been focused including the stages of bottom connection, normal pipe lay and the connection at the FPSO. The main problems associated to the installation phase of the steep wave configuration were identified and addressed in the discussion presented.
As the SSWR configuration has a fixed point at the sea bottom, two different solutions for this connection have been studied, and the final choice is described. The main differences between SSWRs and SLWRs, and the possible advantages of the SSWR configuration are discussed and a direct comparison is presented.
An Extension of the BWH Instability Criterion: Numerical Study
Authors: Storheim Martin , Alsos Hagbart , Hopperstad Odd Sture , Amdahl Jørgen 
Published: October 2015

The BWH criterion for simulating instability prior to necking in sheet metal has been extended with a post-necking damage model, in which the effect of the local neck inside a large element is accounted for with low mesh dependency. The model is incorporated in the explicit FE code LS-DYNA. The material model can be calibrated from a single uniaxial tensile test, and gives good prediction of rupture for a range of stress triaxialities.
This paper investigates the robustness of the criterion through numerical simulations of different experiments, from forming limit tests to large impact experiments on stiffened panel structures. A full-scale collision is simulated with two different mesh-sizes to investigate the robustness of the fracture prediction.
The validation cases are simulated with good accuracy considering the coarse meshes involved. Based on the validation, the post-necking extension of the BWH criterion can readily be used for structural design of offshore structures in order to assess the technical safety level of the structure against collisions in all phases of the design process. The method has a good ratio of accuracy vs. computational cost, and is less prone to user-errors as the calibration is simple and the mesh-scaling is automated.
A Study for Riser Response From Global Dynamic Analysis With Irregular Wave (Continued)
Authors: Zhang Yanqiu , Hou Yucheng , Yuan Jiabei , Tan Zhimin 
Published: October 2015

The results of a study on the statistic properties of the stochastic processes of both irregular wave and riser response were presented in the paper OMAE2014-23196. Following on from that work, the present paper is devoted to the statistic properties of the mean-crossing maxima of the stochastic process of riser response and the statistic properties of the largest maxima, resulting from a number of 3-hour simulations with different wave seeds. The objective of the study is to find a more efficient method for evaluating the most probable maximum (MPM) value of riser response, i.e. using as few as possible simulations to find a reliable expectation to the MPM.
Global dynamic analysis with irregular wave is widely used in riser system design, though it is very time-consuming compared with regular wave. This is because irregular wave can more realistically model the sea state in the field of the riser system compared with regular wave. However time consuming irregular wave analysis may be there remains a perplexing issue, which is the randomness in the analysis results induced by wave seed; i.e. the extreme value of riser response resulting from a 3-hour simulation varies with the wave seed which is arbitrarily selected for the simulation. If a number of 3-hour simulations are performed, then a statistic method is used to evaluate the MPM value, two questions must be answered. First, how many simulations should be run, and second, what statistic method should be used?
Based on the study to the statistic properties of the maxima of riser response and the largest maxima, answers to the above questions are proposed. For universal applicability the study was conducted reflecting four risers which had different configurations and water depths.
Estimation of High Energy Collision Response for Jacket Structures
Authors: Notaro Gabriele , Johansen Atle , Selås Stine Myhre , Nybø Terje 
Published: October 2015

This paper presents a procedure for evaluating the collision response of fixed offshore structures exposed to high energy collisions with Offshore Service Vessels (OSV) or other floating units. A combination of traditional non-linear frame analyses for screening purposes and more detailed non-linear FE analyses using an explicit code is proposed. In the detailed integrated FE analyses, both the fixed offshore structure and the impacting vessel are explicitly modeled as deformable bodies. The progressive changes in contact and the resistance of both deforming objects are fully accounted for, enabling for more accurate results compared to methods where the resistances of the two objects are assessed separately.
Results from case studies are shown. The calculated resistances for the striking objects are compared to the load-indentation curves presented in DNV-RP-C204 [1] and NORSOK N-004 [2].
Design Requirement of a Renewable Energy Plus Compressed Air Energy Storage and Regeneration System
Authors: Finnigan Tim , Roddier Dominique 
Published: October 2015

There are potential offshore applications where renewable energy and more distributed power sources could supplement or replace costly equipment upgrades for additional power supply, or costly fuel operating costs. Renewable energy technologies can also be employed in lieu of expensive power umbilicals to provide power to subsea pumps for long distance tiebacks in deepwater. For example, power umbilicals alone required to provide 69kV to subsea pumps in deepwater could be upwards of $300MM for 100 mile long distance tie-backs. A renewable energy source, with storage, integrated into that system could significantly reduce both the CAPEX and OPEX costs.
In 2013, Chevron performed an in-depth evaluation of a Renewable Energy plus Compressed Air Energy Storage and Regeneration system for a 2.6MW application. For the purpose of that study, a floating wind turbine in 365m water depth off the coast of Oregon was evaluated as the energy source as the base case. The system was found to be feasible with initial CAPEX costs replaced within 12 years of operations as compared to installation of a diesel power generation system and the requisite fuel required to run the equipment.
This paper provides a description of the OCAES system, and discusses potential applications in support of the offshore oil and gas industry.
Exploring Potential of Towing Pipeline in Emergency Scenarios
Authors: Puthiyaparambath Vinod , Kumar Praveen , John Manoj , Stanley Alexander 
Published: October 2015

Subsea pipelines-deemed as the safest and most efficient means for transporting hydrocarbons, their integrity and long term maintenance are among the highest priorities for the oil and gas industry. These assets have a design life and are susceptible to damage from various factors during its operation. Operators should have in place a comprehensive Emergency Pipeline Repair System (EPRS). The EPRS should entail rigorous measures to minimize loss of production, the potential consequences of catastrophes and adverse effects on environment in case of an unforeseen event such as pipeline rupture or spill. The system should ensure swift response to restore the mechanical integrity of a damaged section whilst maintaining high HSE standards and minimizing the production shutdown-time duration. Accidental damages call for remedial response actions on an emergency basis. Considering short lengths of pipeline to be replaced, tow technique can offer an effective alternative to the time consuming and expensive conventional pipe-lay barge operations.
An installation method constituting the tow technique is proposed as a part of EPRS to replace damaged section of an operational pipeline. The paper discusses the applicable scenarios, the installation criteria and operational constraints involved in entire set of activities based on the study undertaken. The scenario analyzed involves launching a pre-fabricated pipe string offshore, towing and lay down at repair location. The pipe string is launched from an onshore facility by means of a lead tug, facilitated by rollers placed at designed intervals. The onerous task of pulling the pipe strings through long stretches of shallow water depths emphasizes the need of neutrally buoyant or slight positively buoyant pipe strings. Placing roller supports for the entire stretch is likely to pose several practical and economic constraints. The pipe string is towed to the intended offshore repair location with the assistance of a trailing tug. The pipe strings are laid down at the intended location in a controlled manner by means of winches and sequential release of buoys.
Numerical models of the system for towing and laydown operations are developed and related investigations are undertaken to evaluate the installation parameters, supplementary buoyancy requirements and to assess the criticality at various stages of installation. Further, the limiting weather criteria to carry out the operation are established based on the wave and current imposed hydrodynamic loadings on the strings and several governing parameters. The paper also briefs merits and limitations of the method.
A Study of Possible Solutions for Cost Efficient Subsea Well Abandonment
Authors: Moeinikia Fatemeh , Fjelde Kjell Kåre , Sørbø Jostein , Saasen Arild , Vrålstad Torbjørn 
Published: October 2015

There is a large number of subsea production wells offshore Norway approaching the end of their lifetime. Considering high spread rate of semisubmersible rigs, abandonment operations of these wells will be quite expensive. Moreover, Plug and abandonment (P&A) can easily contribute with 25% of the total costs of drilling for exploration wells offshore Norway. Hence it is of great importance to seek approaches and solutions to reduce the P&A cost. This paper reviews some possible new ways and also alternative technologies as the solutions to cut down the P&A expenses. Some of these technologies are now being used offshore Norway.
In the first section of this paper, challenges of performing P&A operations offshore Norway together with the main cost drivers are discussed. It is then briefly argued how to consider issues such as barriers setting depth, cementing depth and logging in the design and well construction phases to ease or avoid future P&A challenges. For hydrocarbon exploitation in the Barents Sea and Arctic regions it is important to take into account the P&A phase in the early stage of planning and development.
Light well intervention vessels as alternatives to semisubmersible rigs are recognized of being the largest contributor to cost saving. It will then be discussed to what extent vessel technologies can cut down the expenses for subsea abandonment. New ways of performing P&A can be another contributor to cost saving. It is shown how research and testing can assure the operators of new ways for performing P&A. Retrieval of production tubing is a challenging suboperation such that it imposes significant cost to subsea well abandonment. There have been performed studies on how P&A could be performed with tubing left in hole and it is of interest to pursue this further. We will investigate how the abandonment operations can be simplified and be more cost efficient if the production tubing can be left inside the well where the basic assumptions for being able to do it is accounted for.
In addition, some complexities in abandonment operations can cause additional cost. An example of such complexities can be the need to establish two permanent barriers for potential permeable zones in overburden. It will be demonstrated how much can be saved with respect to cost if the regulations allow to ease some parts of abandonment operations.
In this study, a probabilistic approach as a systematic tool to produce unbiased results is applied to quantify cost savings of new alternatives compared to the traditional ones.
Development and Testing of a Post-Installable Deepwater Monitoring System Using Fiber-Optic Sensors
Authors: Seaman Calvin H. , Brower David V. , Le Suy Q. , Tang Henry H. 
Published: October 2015

This paper addresses the design and development of a fiber-optic monitoring system that can be deployed on existing deep water risers and flow lines; and provides a summary of test article fabrication and the subsequent laboratory testing performed at the National Aeronautics and Space Administration-Johnson Space Center (NASA-JSC).
A major challenge of a post-installed instrumentation system is to ensure adequate coupling between the instruments and the riser or flow line of interest. This work investigates the sensor coupling for pipelines that are suspended in a water column (from topside platform to seabed) using a fiber-optic sensor clamp and subsea bonding adhesive. The study involved the design, fabrication, and test of several prototype clamps that contained fiber-optic sensors. A mold was produced by NASA using 3-D printing methods that allowed the casting of polyurethane clamp test articles to accommodate 4-inch and 8-inch diameter pipes. The prototype clamps were installed with a subsea adhesive in a “wet” environment and then tested in the NASA Structures Test Laboratory (STL). The tension, compression, and bending test data showed that the prototype sensor clamps achieved good structural coupling, and could provide high quality strain measurement for active monitoring.
Mooring Chain Fatigue Assessment Methodology and Software of Williams Gulfstar 1 Spar Platform Using Comparison Between Field Measured Data and the Design Basis Information
Authors: Park Young-Chan (Y. C.) , Antony Arun , Moideen Hisham , Jamnongpipatkul Arada , Hwang Jinsang , Song Duckyong , Gim Hwanseok 
Published: October 2015

In 2014 Williams Companies delivered a Spar-based FPS to be used by the Hess Corporation for developing their “Tubular Bells” field as well as for future tiebacks for other developments. Tubular Bells is located in the Mississippi Canyon region of the Gulf of Mexico.
The Spar hull is the ‘Classic hull form’, 584 ft (178 m) long, 85 ft (26 m) in diameter with 60 ft (18 m) hull freeboard. The mooring system consists of 9 mooring lines in 3 groups composed of a chain-polyester-chain configuration.
This paper describes the tools and methodology Williams plans to use for assessing the fatigue damage of the mooring chain over the operating life of the platform. The basic plan is to collect field-measured data for parameters that impact mooring fatigue damage, such as: environmental conditions, Spar motions (particularly Vortex Induced Motions data) and mooring line tensions, then process that data with specialized software so it can be effectively compared to the applicable data that was used in the design of the mooring system for fatigue.
A key element in the plan to compare the field data with the design data is new computer software developed specifically to process the field measured data and generate the field measured, fatigue design parameters on a regular basis and in a form that is readily comparable to the design data. Additionally, a graphic user interface in this software will provide a clear visualization of the Spar motions that is linked with the associated environmental conditions for the same time periods.
Numerical Solution of 2-D Water Entry Problems Based on a CIP Method and a Parallel Computing Algorithm
Authors: Wen Peng , Qiu Wei 
Published: October 2015

A constrained interpolation profile (CIP) method has been developed to solve 2-D water entry problems. This paper presents the further development of the numerical method using staggered grids and a parallel computing algorithm. In this work, the multi-phase slamming problems, governed by the Navier-Stokes (N-S) equations, are solved by a CIP-based finite difference method. The interfaces between different phases (solid, water and air) are captured using density functions. A parallel computing algorithm based on the Message Passing Interface (MPI) method and the domain decomposition scheme was implemented to speed up the computations. The effect of decomposition scheme on the solution and the speed-up were studied.
Validation studies were carried out for the water entry of various 2-D wedges and a ship section. The predicted slamming force, pressure distribution and free surface elevation are compared with experimental results and other numerical results.
Measurement of Residual Stress Shakedown in Pressure/Tensile Armour Wires of Flexible Pipes by Neutron Diffraction
Authors: Fernando Upul S. , Davidson Michelle , Simpson Christopher , Pirling Thilo , Yan Kun , Callaghan Mark D. , Roy Matthew , Francis John A. , Withers Philip J. 
Published: October 2015

The manufacture of unbonded flexible pipes (flowlines and risers) involves wrapping steel wires to create pressure and tensile armour layers. The forming of armour wires from vendor supply conditions to a helix shape on the pipe involves significant plastic straining and the wires that are wrapped onto the pipe are not unloaded. Therefore the armour wires in flexible pipes are expected to contain significant residual stress (RS) as a result of the plastic straining and loading during manufacture and placement. This may lead to detrimental effects on the strength, durability and the service integrity of the pipe. It is postulated that the unfavorable RS introduced during pipe manufacture reduces due to stress shakedown during the factory acceptance test (FAT) where the pipe is subjected to a high internal pressure.
This paper describes the first attempts to measure RS in the armour wires in unbonded flexible pipes. The key development is the use of a neutron diffraction method which allows the measurement of RS in-situ on the manufactured pipe through the whole wire sections. Pipe samples were prepared exposing the relevant metal layer and the measurements were performed on pipe samples taken before and after performing the pressurized FAT. The effect of the FAT on the shakedown of residual stress in pressure armour wires is discussed. As shown by the measurements, the elastic strains and stresses in the pressure armour wires are much larger in the hoop direction of the pipe (i.e. along the length of the wire) than radial or axial to the pipe. In pre-FAT pipe the hoop stresses are essentially tensile on the extrados and compressive on the intrados. The results have shown that the FAT reduces the hoop strains and stresses to approximately 1/3 of their as manufactured level.
On Prediction for Structural Performance of Ship Side Structures in Head-On Collision Scenario
Authors: Sun Bin , Hu Zhiqiang , Wang Jin 
Published: October 2015

The crashworthiness of ship side structures should be taken into consideration during the structural design phase. When a ship is struck by a head-on collision, the main participants of the side structures include outer plating, longitudinal girders, transverse frames and the stiffeners attached on them. This paper is centered on establishing an integrated deformation mechanism program by identifying the theoretical deformation modes of the side structures, including the plating and stiffeners. The primary failure models of plating structures are the crushing, stretching and tearing modes, and a new crushing model of side plating structures subject to an ellipsoid-shaped indenter is proposed. As for the stiffeners on outer plating, the smeared thickness method is often used, but the role of the stiffeners cannot be traced clearly during the deformation process and the structural performance predictive accuracy may not be guaranteed. Therefore, a theoretical model of stiffeners is established in this paper, on purpose of providing deep insight of the deformation mechanism with reasonable accuracy. The expressions of resistance force of the side structures are also derived based on a study of the progressive deformation process of numerical simulation results and the plastic analytical methods.
The accuracy of the analytical method is verified by numerical simulations using code LS_DYNA. The proposed analytical method can be used for quick assessment of the performances of ship side structures during ship collision.