bluuebunny/crossref_metadata_2025_split huggingface dataset:
CFD Analysis of a LNGC Carrier in Waves
Authors: Guilmineau Emmanuel , Leroyer Alban , Visonneau Michel , Ory Emmanuel 
Published: August 2013

Single Buoy Moorings (SBM) Offshore is a pioneer in the offshore and gas industry. Its product line is the supply of facilities and services for the development and production of offshore oil and gas fields as well as the systems relevant to the mooring technology at large. SBM is currently developing various concepts aimed at offloading LNG (Liquefied Natural Gas) carriers offshore. These concepts whether they assume tandem or side-by-side offloading have in common a building block: the LNG carrier. Owing to its unusual shape (shallow draft, non wall sided hull at the waterline with a flared bow and a transom stern and the presence of a bulb just below the sea surface) at least compared to standard VLCCs (Very Large Crude Carrier), difficulties arise when performing diffraction calculations and when comparing model test results in monochromatic, bi-chromatic and irregular waves with numerical time domain simulations. The main objective is to identify whether differences between model tests and standard numerical predictions based on linear potential theory can be bridged in increasingly complex wave fields by resorting to CFD simulations.
The CFD software used is ISIS-CFD, developed by the Numerical Modelling Group of the Fluid Mechanics Laboratory of Ecole Centrale de Nantes and distributed as commercial software by NUMECA International under the name FINE/Marine.
CFD simulations have been performed in monochromatic head wave condition with and without the 4-line mooring system to prevent the LNG carrier from drifting away. The CFD method is described and a comparison between model tests and simulations is presented. CFD shows that it is able to predict the motions measured in model tests. In addition, both the wave frequency and the natural frequency of the mass spring system are correctly linked with the frequencies of the predicted motions.
Hydro-Mechanical Issues of Offloading Operations Between a Floating LNG Terminal and a LNG Carrier in Side-by-Side Configuration
Authors: Lécuyer Bruno , Ledoux Alain , Molin Bernard , Le Boulluec Marc , Heguiaphal Begnat 
Published: August 2013

This paper presents a state-of-the-art methodology to build a numerical hydro-mechanical model of a floating LNG Terminal with a LNG carrier moored alongside, complying with the physical mechanical behavior and hydrodynamic phenomenology involved in such a complex system.
The required numerical functions are available for intensive engineering applications in the PRINCIPIA’s software DIODORE™ dedicated to sea-keeping and mooring analysis. The methodology has been validated by comparison with non-captive model tests in IFREMER basin in the frame of the SALT 2 JIP led by PRINCIPIA.
The paper describes first the academic side-by-side case that has been tested in basin, associated with the comparison between the experimental results and the numerical application using DIODORE™. In a second step, the main physical parameters of the simulation are analyzed and some gained insights are exposed.
Model Tests for a Floating Windturbine on Three Different Floaters
Authors: Koo Bonjun , Goupee Andrew J. , Lambrakos Kostas , Kimball Richard W. 
Published: August 2013

Wind energy is a promising alternate energy resource. However, the on-land wind farms are limited by space, noise, and visual pollution, and therefore many countries build wind farms near shore. Up to now, most of offshore wind farms have been built in relatively shallow water (less than 30m) with fixed tower type wind turbines. Recently, several countries plan to move wind farms to deep water offshore locations to find stronger and steadier wind fields as compared to near shore locations. For the wind farms in deeper water, floating platforms have been proposed to support the wind turbine.
The model tests described in this paper were performed at MARIN (Maritime Research Institute Netherlands) with a model set-up corresponding to a 1:50 Froude scaling. The wind turbine was a scaled model of the National Renewable Energy Lab (NREL) 5MW, horizontal axis reference wind turbine supported by three different generic floating platforms: a spar, a semi-submersible and a tension-leg platform (TLP). The wave environment used in the tests is representative of the offshore in the state of Maine. In order to capture coupling between the floating platform and the wind turbine, the 1st bending mode of the turbine tower was also modeled.
The main purpose of the model tests was to generate data on coupled motions and loads between the three floating platforms and the same wind turbine for the operational, design, and survival seas states. The data are to be used for calibration and improvement of existing design analysis and performance numerical codes. An additional objective of the model tests was to establish advantages and disadvantages among the three floating platform concepts on the basis of test data.
The paper gives details of the scaled model wind turbine and floating platforms, the set-up configurations, and the instrumentation to measure motions, accelerations and loads as well as wind turbine rpm, torque and thrust for the three floating wind turbines. The data and data analysis results are the subject of another paper in this conference [1].
Comparison of Design and Operational Behaviour of an Offshore Pipeline With Controlled Lateral Buckling
Authors: Solano Rafael F. , Antunes Bruno R. , Hansen Alexandre S. , Bedrossian Arek , Roberts Graeme 
Published: August 2013

It is imperative to adopt some conservative premises in the engineering calculations undertaken during the design stage of an offshore pipeline susceptible to lateral buckling, in order to achieve a design with adequate levels of robustness and integrity throughout the pipeline’s design life. The conservatism can be attached to many uncertainties such as the pipe-soil interaction — interpreted as-soil friction factors — the seabed stiffness and profile and even the as laid lateral out-ofstraightness. Once in operation, these effects will come into play and the pipeline may behave slightly differently to that anticipated in design, depending on the relative strength of the natural uncertainties compared to the design features such as engineered buckling triggers. The over-riding intention in design is, of course, to enable the pipeline to withstand, with sufficient safety margins, the maximum stresses and strains anticipated to occur by realistic predictions in the design stage.
In recent years, many kilometres of deepwater pipelines have been designed and installed along the Brazilian coast using the principle of controlled lateral buckling, in which engineered buckle triggers, such as sleepers and distributed buoyancy sections, are deployed at regular intervals along the pipeline. The purpose of these triggers it to initiate a sufficient number of benign buckles along the pipeline and thereby relax the compressive forces set up as a result of thermal expansion without violating safe limits on stress and strain in the pipelines. In addition to the engineered buckling sites, however, the natural seabed features and associated uncertainties will interact with the pipeline’s behaviour and create additional natural buckle sites. To anticipate these sites and discover their importance at the design stage is recognised as a real challenge, particularly as precise post-installed and in-operation surveys are not normally carried out with the intention of confirming such buckle sites and design assumptions.
The work reported in this paper is a detailed comparison between the initial design and observed operational behaviour of an offshore HP/HT pipeline, mainly in terms of the engineered and natural buckles actually formed along the pipeline, the severity of these buckles and some conclusions concerning the effects of initial imperfections and pipe-soil interaction characteristics considered in detailed design. It is hoped that this rare feedback from real operating conditions on installed pipelines, will be of great interest to pipeline designers and lead to more efficient and better understood design processes and encourage Operators to undertake more regular and sophisticated surveys of operating and installed pipelines for the benefit of future projects.
Ensemble Forecasts Used for Extreme Wave Warning and Platform Unmanning Strategies
Authors: Hagen Øistein , Riise Bjørn 
Published: August 2013

Surface waves often represent the most critical environmental parameter for offshore activities, and reliable forecasts are in many cases essential for safe operation.
Currently, decisions on safety during extreme wave situations are generally taken based on deterministic wave forecasts, and uncertainty related to forecasts are acknowledged and accounted for via safety margins. However, unmanning criteria reflecting a consistent probabilistic model for the forecast uncertainty are generally lacking.
In 1998 the European Centre for Medium-Range Weather Forecasts (ECMWF) introduced a new method for ocean wave forecasting based on the Ensemble Forecasting technique. In this paper we address how the ensemble prediction system (EPS) can be used to establish a probabilistic model applicable for platform unmanning criteria and procedures.
Before ensemble forecasting techniques can be introduced operationally for this purpose it is important to investigate how the decision process can be improved with this method. By improvement we expect the probability forecasts to yield a higher hit rate and a lower false alarm rate.
Extreme wave warnings are simulated based on a data series established for a 10-year period and the hit and false-alarm rate from deterministic and probabilistic forecasts are compared with measured data. The ensemble forecasts are used to:
• establish a model for uncertainty of forecasts for bad weather
• update safety margins used at present such that target safety is obtained if deterministic forecasts are used
• discuss a revised scheme where the EPS forecasts are applied on an operational level
Hebridean Marine Energy Resources: Wave-Power Characterisation Using a Buoy Network
Authors: Vögler Arne , Venugopal Vengatesan 
Published: August 2013

The Outer Hebrides of Scotland were identified as an area with a high wave power resource of 42.4kW/m. The Outer Hebrides of Scotland are currently targeted by a range of developers for demonstration and commercial developments of wave energy converters and current planning efforts are based on initial deployments by 2014. Technology providers with well advanced plans to develop the Hebridean wave resource include Aquamarine Power (Oyster) [1], Pelamis (P2) [2] and Voith Wavegen (OWC) [3]; all of these companies are partners in the Hebridean Marine Energy Futures project [4] to help move the industry into the commercialisation stage.
As part of the Hebridean Marine Energy Futures project, a three year programme aimed at developing a high resolution wave energy resource map to support the site selection process of marine energy developers, a network of three wave measuring buoys was deployed 15km offshore in a depth of 60m and at distances of 11km between buoys. Measured wind and wave data from this buoy network for autumn 2011 are analysed and presented in this paper along with estimated wave power for the same duration.
SCR VIV Analysis Using Time Domain Code SimVIV
Authors: Sidarta Djoni E. , Rakshit Tuhin , Jaiswal Vivek 
Published: August 2013

Vortex Induced Vibration (VIV) analysis of risers using time domain Finite Element Analysis (FEA) captures nonlinearity in the system. Such non-linearity may be in the form of boundary conditions or the imposed loadings. Riser VIV analysis using a frequency domain code has to linearize the system, such as imposing linearized boundary conditions.
Non-linear boundary conditions for steel catenary riser (SCR) could be in the SCR-soil interaction and in the hang-off system. An SCR is often supported by a flex joint that has non-linear rotational stiffness. The effect of these non-linear boundary conditions in SCR VIV response is investigated in this paper.
In addition, the effect of the directions of current profiles with respect to the riser on the SCR VIV response is also investigated. Comparison to standard industry practice, that is applying currents either in the plane or normal to the plane of the SCR, is presented.
Time domain VIV code SimVIV coupled with FEA code ABAQUS was used in the analysis.
Determination of Infragravity Wave Conditions at a Nearshore Location With a Non-Uniform Coastline: Case Study of Baía de Todos os Santos, Brazil
Authors: van der Hout Arne J. , de Jong Martijn P. C. , Moerman Emiel , Timerman Gabriela J. , Ribeiro Eric Oliveira 
Published: August 2013

The Petrobras energy company plans to build a new terminal in the Baía de Todos os Santos, Brazil. This paper describes a study in which an estimate has been provided for infragravity (or low-frequency, LF) wave conditions at this future LNG Regasification Terminal location. To aid the design of the terminal, numerical simulations of the propagation of these waves into the bay have been performed.
At the proposed terminal location, within a large coastal bay, LF waves can be related to long waves bound to the local primary sea and swell waves (bound LF waves) and to low-frequency waves that propagate into the bay after being made free near the bay entrance (free LF waves). While most of the primary waves will not fully penetrate into the bay, the long LF waves can. Due to the large area of the bay (approximately 40 km × 30 km), detailed modelling of all complex coastal processes related to infragravity waves was not efficient. Therefore, a practical approach has been followed in this study.
For a first evaluation, an estimate has been made of bound LF wave conditions at the terminal location inside the bay and at the mouth of the bay. This estimate is based on an equilibrium method using the local primary wave climate and assuming a flat bottom. In a second stage, free LF wave penetration into the bay has been simulated using the shallowwater model Delft3D-FLOW.
By applying the practical approach described in this paper, infragravity wave conditions (bound and free) have been efficiently estimated at the future terminal location for yearly-averaged and extreme primary wave conditions. The results show that the LF wave climate at the terminal will be very mild, corresponding to beneficial conditions for terminal operations. The outcome of this study will be taken into account in the further design of the terminal.
Station Keeping and Propulsive Performance of a DP Crane Barge Close to a FPSO: A Comprehensive Set of Experimental Tests
Authors: Tannuri Eduardo A. , Moratelli Lazaro , Vileti Vinícius L. , Silva João Luis B. 
Published: August 2013

DP crane barges operate in close proximity to FPSO (Floating Production Storage and Offloading) during lifting operations. This operation is critical since small variations of the relative position may result in collision between the bodies or large motion of the lifting load. The hydrodynamic interactions between the units are an important effect that must be considered in the analysis of those operations. The interactions are an intricate problem that cannot be modeled analytically in an appropriate way. Hence, experimental and numerical tools are applied for the definition of the environmental conditions for a safe operation or the optimal relative positioning between the vessels.
A research project conducted by Petrobras in cooperation with Brazilian universities aims to develop and to validate numerical tools for aiding the design and analysis of the DP lifting operations. They are based on dynamical time-domain simulations of the operation and can be used for predicting several parameters of the operations. The experimental tests that will be used for validating this numerical model, concerning the DP performance when the crane barge is close to a FPSO, are presented in this paper. The tests were conducted in an ocean basin using the model of a moored FPSO and the DP crane barge. The station keeping ability (relative motion) and the performance of the propulsive subsystem of the DP crane barge (power and thrust utilization parameters) are measured. Several relative positions and wave conditions were considered.
A General Approach for DP Weathervane Control: Numerical Results
Authors: Miyazaki Michel R. , Tannuri Eduardo A. 
Published: August 2013

With oil exploration occurring at increasing distances from the shore, the use of DP vessels becomes economically attractive for oil transfer and transportation. This operation has some peculiarities, such as the possibility to arbitrarily set the DP vessel heading.
Setting the correct yaw angle brings advantages to the vessel such as reducing the fuel consumption and minimizing the DP system output. However, it is not trivial to calculate the optimum heading, due to uncertainties at wave and current estimation. Moreover, these factors are not constant along time, and to keep the optimum position, the system must adapt with the changes.
A method to update the heading Set-Point based on the theory of Zero Power Control was developed, which has advantages over other weathervane control methods, such as an effective control of all horizontal movements and the possibility to control any reference-point, not only points located the vessel bow.
A fully non-linear dynamic simulator was then used to carry out a complete analysis of the controller.
Effect of Mud Shedding on Riser Anti-Recoil Control at Emergency Disconnect
Authors: Li Songcheng , Campbell Mike , Howells Hugh , Powell Simeon 
Published: August 2013

With drilling capability extends to water depths up to 3000m, significantly increased is the risk associated with a failed riser recoil control in the event of an emergency riser disconnect due to loss of vessel station keeping. In deeper waters the tensioner system undertakes higher top tension due to the accumulation of riser length and mud weight. During emergency disconnect, the riser is disconnected between the blow-out preventer (BOP) and the lower marine riser package (LMRP), releasing the base tension and mud pressure. Impact between the top riser system and the diverter housing system should be avoided, and the clearance between the LMRP and BOP should be secured. Efforts have been continuously made in the industry to achieve a more accurate predict of the riser recoil response. The relevance of mud discharge to recoil control has been widely discussed but little quantitative data has been revealed in the literature.
In this paper, effect of mud shedding on riser recoil response is discussed. The Herschel-Bulkley rheology model is utilized for mud flow and is considered the latest advance in the drilling industry. Water hammer theories with column separation are modified to account for mud discharge in laminar, transitional and turbulent flow regimes.
As a case study herein, recoil response of a drilling riser attached to a dynamically positioned semi-submersible drilling vessel is assessed to present the mud discharge effect on riser anti-recoil control. At emergency events, the riser is disconnected above the BOP, which is located at a water depth of about 2150m for this study. Mud is generally preferred to be freely discharged during an emergency disconnect for ease of anti-recoil control and riser integrity. The density difference between drilling mud in the riser annulus and sea water outside the riser outer casing before disconnect induces a high pressure difference, which drives mud shedding at riser disconnect. Mud flow rate plays an important role in the speed control of the riser uplift. 3D finite element analysis is performed in time domain to simulate riser response before and after disconnect. 2HRECOIL software is integrated into ANSYS user programmable features to better model the riser response and mud discharge.
Application of 7%Ni-TMCP Steel Plate to Large Scale LNG Storage Tank
Authors: Onishi Kazushi , Kawabata Tomoya , Kamo Takahiro , Tanino Yuichi , Yamashita Maki , Iida Atsushi , Kusagawa Masaki , Nishigami Hiroshi , Sakato Naokazu , Mitsumoto Masahiko , Hirai Syuichi , Hirose Hitoshi , Hagihara Yukito 
Published: August 2013

Increase of natural gas demand has led the increase of constructions of Liquefied Natural Gas (LNG) storage tanks worldwide. The inner tank material for above ground LNG storage tanks has mostly been made of 9% nickel steel plate over the last 50 years as it has excellent mechanical properties under the cryogenic temperature of −160deg.C. During this period, the LNG storage tanks made of 9%Ni steel plate have safely been operated. Meanwhile, technologies of steel making, welding, design, construction and inspection of 9%Ni steel plate have been improved significantly and enable us to achieve enlarging volumetric capacity of the tank to 2–3 times.
It is known that nickel is an expensive and valuable rare metal and recent tendency of increase in nickel price has influenced the price of 9%Ni steel plate. In such a circumstance lowering the Ni content would save cost and this has led to an extensive research and development resulting in the 7%Ni-TMCP steel plate. This 7%Ni-TMCP steel plate developed is characterized by adjustment of chemical compositions and application of suitable Thermo-Mechanical Controlled Process (TMCP).
In order to evaluate fitness of the 7%Ni-TMCP steel plate and its weld for LNG storage tanks, a series of testing was conducted. Several different kinds of plate thicknesses from 6 to 50 mm were chosen to run large scale fracture toughness tests such as duplex ESSO tests, cruciform wide plate tests as well as small scale tests. As a result it was demonstrated that the 7%Ni-TMCP steel plate had a quite excellent resistance to brittle fracture of the inner tank steel and its welds exposed to the cryogenic temperature of LNG.
Furthermore, other various issues such as extent of applicable heat input, repair weld, difference of physical constants and so on were investigated and found acceptable.
In Japan Ministry of Economy, Trade and Industry (METI) approved to apply this steel to new LNG storage tanks of Osaka Gas. After that Osaka Gas decided to construct a new full containment LNG storage tank applying 7%Ni-TMCP steel in Senboku terminal 1. The capacity is 230,000m3, which is larger than present largest scale of 180,000m3 in Japan. The construction is planned to start in September 2012 and be completed by November 2015.