bluuebunny/crossref_metadata_2025_split huggingface dataset:
Human Injury Probability During Water Entry of Free-Fall Lifeboats: Operational Criteria Based on Long-Term Simulations Using Hindcast Data
Authors: Fouques Sébastien , Sauder Thomas , Reinholdtsen Svein-Arne , van Dam Esra , Uittenbogaard Jeroen 
Published: September 2014

The paper addresses the safety of occupants in free-fall lifeboats launched from turret-moored floating production, storage and offloading (FPSO) vessels. It presents a methodology for assessing operational limits with respect to acceleration-induced loads experienced by the passengers during water entry. The probability of being injured is estimated by means of numerical simulations for several seat rows and in various sea states described in terms of significant wave height and mean wind velocity. Those results are therefore practical for on-site decisions regarding the use of the free-fall lifeboats.
The numerical simulations performed to estimate the 6-degrees of freedom (6-DOF) water entry accelerations in the lifeboats are based on more than 50 years of hindcast metocean data. These consist of sea state parameters provided every third hour and including the significant wave height, the peak period and the direction of both wind-sea and swell as well as the direction and mean velocity of the wind. In a first step, the motion of the FPSO is computed for the whole time period covered by hindcast metocean data, using a state-of-the art numerical model validated against experimental data. The model includes nonlinear excitation forces, a dynamic positioning system with a realistic heading control strategy, mooring line forces as well as turret-hull coupling. The obtained FPSO motion is then used in Monte Carlo simulations of lifeboat launches performed for selected time windows in the original metocean hindcast database corresponding to selected intervals of the significant wave height and mean wind velocity. In addition to the 6-DOF skid motion, the lifeboat launch simulations account for the effects of wind and waves diffracted by the FPSO hull.
Finally, a probabilistic model describing the joint-distribution of several injury types and water entry acceleration parameters computed through the launch simulations is used to evaluate the injury probability. The results are presented in term of seating matrices showing critical seat rows, in which the probability of being injured exceeds a pre-defined threshold.
The Hydrodynamic Performance of a Twin-Hull FLNG Concept
Authors: Schut Xavier , de Boom Wim 
Published: September 2014

This paper presents the results of a numerical and experimental study concerning the hydrodynamic performance of the SBM midscale Twin-Hull FLNG concept. SBM’s innovative design consists of two LNG carriers joined together, and converted into a single FLNG facility. This option provides both sufficient deck space and storage capacity while having the benefit of a conversion project, being reduced delivery schedule and lower costs. This results in an unusually wide vessel for which only very limited number of precedents exist.
Important hydrodynamic performance indicators such as first order motions, green water and bottom slamming are investigated by means of sea keeping tests. In these tests the scale model of the FLNG is subjected to moderate and harsh environmental conditions from various headings. The results are used to verify the numerical predictions of the global motions, wave drift forces and internal loads and to assess green water and bottom slamming loads.
Current coefficients were calculated by computational fluid dynamics (CFD) and validated with wind tunnel experiments. All load components (wind, wave, current) are then used to evaluate the ability of the vessel to weathervane. This paper presents the investigation of the quality of numeric predictions by comparing model test data against numerical data and hence it summarizes the hydrodynamic performance of the Twin-Hull.
Seismic Reliability of a Fixed Offshore Platform Against Collapse
Authors: Dyanati Mojtaba , Huang Qindan 
Published: September 2014

As many jacket type steel platforms have been constructed in the highly active seismic area, seismic reliability evaluation of such structures is desirable. Ultimate limit state (ULS) with base shear capacity and demand can be used to estimate seismic performance of fixed offshore platform against collapse. Base shear capacity is evaluated from pushover analysis on a 3D finite element model of the offshore structure using different load patterns. Base shear demand is calculated from spectral acceleration at a given site and the total mass of the platform. Uncertainties are considered in both capacity and demand evaluations.
With the limit state function, seismic fragility of a prototype structure is assessed using reliability analysis. The results indicate that various load patterns affect the seismic performance evaluation. It is also found that the steel yield stress is a critical parameter in the reliability of the steel jacket platforms.
Generation of Multivariate Wave Conditions as Input for a Probabilistic Level III Breakwater Design
Authors: Mercelis Peter , Dufour Marc , Alvarez Gebelin Ariel , Gruwez Vincent , Doorme Sarah , Sas Marc , Leyssen Gert 
Published: September 2014

For an offshore LNG project situated in the estuary of the Rio de la Plata nearby Montevideo, Uruguay, it was required to verify the deterministic design of the protective rubble mound breakwater and the jetty infrastructure with a level three probabilistic design. Therefore, in first instance extreme site conditions were required both in front of and behind the breakwater.
To obtain these conditions, the first step is to extrapolate the offshore variables in order to translate them to the breakwater location. All the possible combinations of extreme wind, water level and waves are quantified with a probability of occurrence. A combination of univariate extreme value distributions, copula’s and regression is used to describe the multivariate statistical behaviour of the offshore variables. The main variable is the wind velocity, as in the area of concern extreme wave conditions are wind driven. The secondary variable is water level. Wind velocity and water levels are only correlated for some wind directions. For these directions, wind velocity and water level extreme value distributions are linked through a multivariate Gumbel Copula. The wave height at the model boundaries was taken into account by a regression function with the extreme wind velocity at the offshore location and the wave period by a regression function with the wave height.
This way 1515 synthetic events were selected and simulated with the spectral wave model SWAN, each of which a frequency of occurrence is calculated for. However, due to refraction and diffraction effects of the approach channel (in the area of concern water depths are limited to about 7 m and the navigation channel has a depth of about 14 m), the port basin and the breakwater itself, the spectral wave model SWAN is not sufficient to accurately calculate the local wave conditions in the entire area of interest. Therefore a non-linear Boussinesq wave model (i.e. Mike 21 BW) was set up in addition, using input from the spectral model at the boundary and including the navigation channel of more than 12 km long. Combining both models, significant wave heights are obtained on both the seaward side and the leeside of the breakwater with corresponding frequencies of occurrence. This approach allows the determination of conditional return periods and generates the site conditions required for a probabilistic level three design of the breakwater and the jetty infrastructure taking for example the joint probabilities between waves and water levels fully into account as needed for overtopping or failure calculations.
Incorporating Engineering Criteria to the Synthesis and Optimization of Submarine Pipeline Routes: On-Bottom Stability, VIV-Induced Fatigue and Multiphase Flow
Authors: Baioco Juliana Souza , Stape Philip , Granja Marcelo , Albrecht Carl Horst , de Lima Beatriz Souza Leite Pires , Jacob Breno Pinheiro 
Published: September 2014

In offshore field development it is extremely important to plan the submarine pipeline route for the hydrocarbons transportation. To ensure an expedited project, researchers from Petrobras and LAMCSO/COPPE/UFRJ have been involved in the development and implementation of a computational tool, based on Evolutionary Algorithms, for the synthesis and optimization of submarine pipeline routes. In this tool, each candidate route is evaluated in terms of several criteria that are incorporated in an objective function, to take into account the relevant aspects that should be considered in the design of a route, such as the pipeline length, bathymetry data, obstacles, number and length of free spans and others.
Previous works described the incorporation of engineering criteria related to on-bottom stability and VIV-induced fatigue in free spans for pipes under the action of hydrostatic and hydrodynamic environmental loads of current and waves. Now, this work presents more examples of applications related to this latter criterion, and focus on the incorporation of a production criterion related to the pressure drop due to multiphase fluid flow, according to correlations for inclined pipelines.
The goal is to obtain a robust tool to reduce the design time and minimize the cost of the pipeline route, leading to an optimal route configuration complying with various engineering criteria that, on a traditional design procedure, would be checked separately only after the definition of the route.
Development of Time Domain Model for Synthetic Rope Mooring Systems
Authors: Kaasen Karl E. , Lie Halvor , Wu Jie , Falkenberg Erik , Åhjem Vidar , Larsen Kjell 
Published: September 2014

Mooring of offshore structures in very deep water has been made possible through the use of lines made of fibres of synthetic material. The mechanical behaviour of synthetic ropes is considerably more complex than that of steel wire rope and chain, due to the visco-elastic and visco-plastic properties of the synthetic material. In particular, the gradually developing permanent increase in rope length will affect the offset and motion of the moored structure and make its characteristics change from one storm to the next.
For design and analysis of offshore mooring systems incorporating synthetic ropes it is valuable to have good models that can be used for response simulation in the time domain. The paper describes the development of a time domain model for synthetic rope. The model structure and the values of the parameters are determined from experimental data using a system identification technique. The resulting model is implemented in an existing computer program for analysis of mooring and riser systems. In particular, the permanent elongation of the synthetic rope appears to be well represented.
Experimental Validation of a Numerical Model for a Dry-Tree Semisubmersible in Benign Environments
Authors: Martin Bruce , Rijken Oriol , Davies Kent 
Published: September 2014

The offshore industry has spent the last several years developing semisubmersible platforms capable of supporting both drilling and production activities. The production trees are located on top of the top tensioned risers (TTRs) on a Dry Tree Semisubmersible. A key challenge in the design of these vessels is to reduce the heave motion as much as possible to enable the use of state-of-the-art riser tensioners. A model test campaign was executed as part of the developmental program. The primary objective of this campaign was to improve the accuracy of the numerical tools to be used in the design process.
Riser tensioners are typically hydro-pneumatic devices, with a nonlinear tension-stroke relationship. A riser tensioner was developed at model scale which had a similar nonlinear behavior to the prototype. Examining the effect of this tensioner on the global motions was an additional objective of this test campaign. The techniques used to model this nonlinear spring is described, and its effect on global motions investigated.
A key challenge in model testing platforms intended for ultra-deep water (e.g. greater than 7000 ft) is the modeling of the mooring and riser system. The premise for the design of the model mooring system is 1.) maintain as best as possible the force-offset relationship of the mooring lines and 2.) be able to describe the model test configuration in the numerical tools to be used for global design. The near taut behavior of the prototype mooring system is modeled using heavy chain and a high-catenary mooring line.
Modular Mathematical Model for a Low-Speed Maneuvering Simulator
Authors: Tannuri Eduardo A. , Rateiro Felipe , Fucatu Carlos Hakio , Ferreira Marcos Donato , Masetti Isaias Q. , Nishimoto Kazuo 
Published: September 2014

This paper presents the mathematical model of the real-time ship simulator for low-speed maneuvering developed by the University of São Paulo, Transpetro and Petrobras, with the technical collaboration of Brazilian Pilots Association (CONAPRA). The software is based on the TPN (Numerical Offshore Tank) numerical code which had several modifications, in order to perform real-time simulations.
After the complete description of the mathematical model, some illustrative results of simulations executed with pilots are exposed.
Effects of Strake Coverage and Marine Growth on Flexible Cylinder VIV
Authors: Resvanis Themistocles L. , Rao Zhibiao , Vandiver J. Kim 
Published: September 2014

In this paper we present some results from the recent SHELL tests at the MARINTEK basin. The tests involved towing densely instrumented flexible cylinders at Reynolds numbers up to 220,000. The main objective is to present the experimental results describing the effectiveness of different amounts of strake coverage and to explore the influence of simulated marine growth.
The data is presented in terms of CF response amplitudes and rainflow-counted damage rates due to the combined CF and IL bending stresses. All results are compared with the bare cylinder cases which will be used as a reference to determine how effective the strakes are in suppressing VIV and how this effectiveness can be affected by marine growth. The results show that even small bare sections (missing strakes) can lead to significant VIV response. We also observe that moderate amounts of marine growth can quickly negate any suppression coming from the strakes.
FEA Analysis of Subsea PLET Installation and Operation
Authors: Wang Shuqin , Zhang Jiaping , Malachowski Jim , Schattenberg Diane , Ji Jason 
Published: September 2014

Pipeline end termination (PLET) has been widely used in subsea field development. One challenge in the deployment of a PLET is monitoring the real-time stress condition in different components at different phase. Those components include mudmat, piping pipe system, yoke and upper structure. From load out on a barge to the field, to be settled for normal operation condition as well as recovery process, finite element analysis (FEA) could be utilized to simulate this process, minimize the material cost and optimize the design.
The scope of the current paper is to proposal a FEA simulation methodology to analyze this PLET loading process. This basic idea is to use one CAD model with all details to cover the entire simulation process, for all loading phases. The result has been approved to yield reasonable prediction of the real project with major clients. The methodology showed great potential value to be shared with the entire industry.
Performance Specifications for Real-Time Hybrid Testing of 1:50-Scale Floating Wind Turbine Models
Authors: Hall Matthew , Moreno Javier , Thiagarajan Krish 
Published: September 2014

This paper presents performance requirements for a real-time hybrid testing system to be suitable for scale-model floating wind turbine experiments. In the wave basin, real-time hybrid testing could be used to replace the model wind turbine with an actuation mechanism, driven by a wind turbine simulation running in parallel with, and reacting to, the experiment. The actuation mechanism, attached to the floating platform, would provide the full range of forces normally provided by the model wind turbine. This arrangement could resolve scaling incompatibilities that currently challenge scale-model floating wind turbine experiments.
In this paper, published experimental results and a collection of full-scale simulations are used to determine what performance specifications such a system would need to meet. First, an analysis of full-scale numerical simulations and published 1:50-scale experimental results is presented. This analysis indicates the required operating envelope of the actuation system in terms of displacements, velocities, accelerations, and forces. Next, a sensitivity study using a customization of the floating wind turbine simulator FAST is described. Errors in the coupling between the wind turbine and the floating platform are used to represent the various inaccuracies and delays that could be introduced by a real-time hybrid testing system. Results of this sensitivity study indicate the requirements — in terms of motion-tracking accuracy, force actuation accuracy, and system latency — for maintaining an acceptable level of accuracy in 1:50-scale floating wind turbine experiments using real-time hybrid testing.
Bilge Keel Influence on the Free Decay of Roll Motion of a Three-Dimensional Hull
Authors: Yeung Ronald W. , Jiang Yichen 
Published: September 2014

The prediction of roll motion of a ship with bilge keels is particularly difficult because of the nonlinear characteristics of the viscous damping. Flow separation and vortex shedding caused by bilge keels significantly affect the roll damping and the magnitude of the roll response. To predict free response of roll, the Slender-Ship Free-Surface Random Vortex Method (SSFSRVM) developed in Seah & Yeung (2008) [1] was employed. It is a fast free-surface viscous-flow solver designed to run on a standard desktop computer. It features a quasi-three dimensional formulation that allows the decomposition of the three-dimensional hull problem into a series of two-dimensional computational planes, in which the two-dimensional free-surface Navier-Stokes solver FSRVM [2] can be applied. This SSFSRVM methodology has recently been further developed to model multi-degrees of freedom of free-body motion in the time domain. In this paper, we will first examine the effectiveness of SSFSRVM modeling by comparing the time histories of free roll-decay motion resulting from simulations and experimental measurements. Furthermore, the detailed vorticity distribution near a bilge keel obtained from the numerical model will also be compared with the experimental PIV images. Next, we will report, based on the time-domain simulation of the coupled hull and fluid motion, how the roll decay coefficients and the flow field are altered by the span of the bilge keels. Plots of vorticity contour and vorticity iso-surface along the three-dimensional hull will be presented to reveal the motion of fluid particles and vortex filaments near the keels.
It is appropriate and an honor for me to present this roll-damping research in the Emeritus Professor J. R. Paulling Honoring Symposium. It was from “Randy” that I first acquired the concept of equivalent linear damping. Even more so, I am very grateful for his teaching, guidance and friendship of many years. — R. W. Yeung
Validation of Floating Behavior of a Robinson R66 Helicopter After a Water Landing
Authors: Peiffer Antoine , Taft Dale , Lum Alan , Roddier Dominique 
Published: September 2014

This paper summarizes the hydrodynamic work that was performed on the Robinson R66 helicopter’s water emergency landings as part of the roadmap to obtain FAA approval. The emergency system consists of two floats that are rapidly inflated as soon as the helicopter touches the water using gas from a high pressure cylinder. This type of design is common in the helicopter industry and is known as a “pop out” float system. The floats have already been shown to provide enough buoyancy to keep the helicopter afloat in calm water.
Recognizing that once the helicopter is in the water, it is subjected to wave forces and behaves as a small water craft, a numerical study was performed using OrcaFlex. Over 500 numerical simulations, each lasting 10 minutes, of the helicopter floating in different wave environments were performed. The helicopter’s 6 degree-of-freedom (DOF) motions were monitored throughout. At the end of the run, if the helicopter had not capsized, the run would report: “no capsizing”. Sensitivity studies were performed by varying parameters individually. This led to an understanding of each parameter’s effects on the overall helicopter floating performance. These parameters included: wind, wave period, initial helicopter relative heading against the waves, wave height, and simulation seed (different random wave sets with the same spectral characteristics). The FAA expects floatation characteristics to be evaluated in “reasonably probable” water conditions and has issued guidance that World Meteorological Organization (WMO) sea state 4 is one acceptable definition of reasonably probable. A wind speed of up to 21 knots is also associated with sea state 4.
Heavy Wall Linepipe Girth Weld Fatigue Strength: Investigating Weld Root Performance
Authors: Marines-Garcia Israel , Mota Noe , Darcis Philippe P. , Quintanilla Hector M. , Kan Wan C. , Ghosh Rupak , Visco Tyler 
Published: September 2014

The feasibility of Heavy Wall (HW) Seamless Line pipe application for high pressure/high temperature deep and ultra-deep field developments must be experimentally demonstrated to establish acceptable performance. Detailed mechanical, corrosion and fatigue qualification programs are required for validation of heavy wall line pipe and the associated girth welds for riser and flowline systems, especially those in fatigue-critical applications.
Pipe manufacturers and Operators share a common interest in developing new technologies to economically and safely produce from challenging reservoirs. In OMAE 2013, Tenaris and ExxonMobil jointly presented the Phase 1 qualification effort performed on HW line pipe and associated girth weld via mechanical and full scale fatigue testing. The results confirmed the mechanical properties were acceptable and the fatigue performance of the associated girth welds was reasonable. As expected, most of the fatigue failures originated at the outer pipe surface. As such, the focus of the present work is to further examine the fatigue performance considering fatigue failure initiation at inner pipe surface. This would provide a better assessment of riser and flowline fatigue performance for applications where the inner pipe surface is subjected to degradation from potential aggressive components in produced fluids.
To investigate the root girth weld fatigue performance, the adopted plan was to create an outer surface free of stress raisers/imperfections at weld cap toe which would help “push” the fatigue initiation to the root weld toe at the inner pipe surface. To achieve this, an enhanced grinding and flapping technique on the fatigue test specimen external surface was applied to remove the cap overfill and produce the desired flush profile. The same surface treatment technique was also applied on the pipe body in the proximity of the girth welds.
This program utilized identical pipe and girth weld used for the Phase 1 qualification effort. The heavy wall pipe was an X65, 10 ¾″ OD × 46 mm WT. The welding procedure was a narrow-groove bevel, STT® process for the root pass and the GMAW process for hot, fill, and cap passes. Four full scale fatigue tests were conducted for this investigation, two girth welds per fatigue specimen. In the end, the enhanced surface treatment technique was successful in “pushing” the fatigue failure initiation to the inner pipe surface. This paper presents the fatigue performance results due to crack initiation at the inner pipe surface as well as post-mortem analyses of the failure surfaces.