bluuebunny/crossref_metadata_2025_split huggingface dataset:
Moonpool Effect Assessment During Structure Installation
Authors: Perez Gabriel Vazquez , Pistidda Alessio , Smienk Henk 
Published: September 2014

Heerema Marine Contractors (HMC) is entering a new era of pipe laying with the new Deep water Construction Vessel (DCV) Aegir, which is designed to be able to reel/J-lay pipelines for a wide range of pipe dimension and water depth combinations. The DCV Aegir has a moonpool close to the center of the vessel in which the Hang Off Module (HOM) for pipeline installation is positioned. The HOM is utilized to hold the pipeline and its structures during installation [1]. Pipelines and its structures will be lowered through the moonpool. When a pipeline structure is lowered through the moonpool the HOM is retracted, thus clearing the moonpool to allow the free pass of the structure.
The behavior of the water in the moonpool will induce loads on the structures when these are being lowered. These loads will induce motions and bending moments on the attached pipeline. The effect of the moonpool on the structure has to be known in order to assess the integrity of the pipe (fatigue and local buckling limit state) and the optimal procedure for structure installation.
The assessment of the moonpool effect on the structure during the lowering through the splash zone is complex because it is governed on one side by the motions of the vessel and on the other side by the motion of the water inside the moonpool.
This paper will focus on the moonpool effect assessment in a Pipe Line End Termination (PLET) installation analysis. Two different software packages are utilized; Flexcom of MCSKenny and STAR-CCM+ of CD-Adapco.
Flexcom is used to reproduce the vessel motions which affect the PLET motion behavior. Pipe properties (OD, WT and length) and PLET together with pipelay equipment; such as Upper Tensioner (UT), HOM, Pipe Wire Centralizer (PWC) and winch, are modelled.
To assess the hydrodynamic loads on the PLET inside the moonpool a Computational Fluid Dynamics (CFD) approach is required. STAR-CCM+ is a CFD program which uses Finite Volume Method (FVM) to solve the flow field motion equations. With this software it is possible to accurately model the geometry of the PLET and simulate the interaction between water in the moonpool and the PLET.
The paper will present an overview of the models and the analyses performed, together with the methodology used to combine the outcome of both software packages.
Underwater Sound and Vibrations due to Oil and Gas Activities
Authors: van Beek Pieter , Binnerts Bas , Nennie Erik , von Benda-Beckmann Sander 
Published: September 2014

In the oil & gas industry there is a trend towards more subsea activities. To improve gas recovery from existing and new fields at greater depths, the produced gas will be compressed, processed and transported via subsea templates and underwater networks (pipelines, flexible risers, etc.). Besides the huge consequences for the subsea installation itself (reliability, maintenance, etc.), it also has consequences for underwater wildlife through the underwater source vibrations leading to sound radiation. Regulations aimed at managing the impact of underwater sound on marine life have been put in place by different nations [e.g. 1,2]. Many offshore operations require an assessment of the potential impact of underwater noise on the environment, which requires knowledge of the sound transmitted by the subsea components.
Until now very little is known about the underwater source mechanisms, the acoustic strength of these underwater networks, the coupling of the emitted source sound to the surrounding medium and the impact of the sound on the underwater wildlife. The dynamic behavior of networks for compressing and transporting gas, and the translation into emitted noise into air are rather well understood. However, due to the presence of the water the dynamic behavior from such subsea installation is very different than in air. To predict the dynamic behavior, the presence of the water cannot be neglected and has to be taken into account.
This paper presents a simplified model for a subsea high speed turbo-compressor coupled to the KrakenC normal mode propagation model. With this combined model the noise at remote locations can be predicted and compared with the ambient noise and other anthropogenic noise sources such as for instance shipping, dredging and wind farm operation noise.
Development of a Scaled-Down Floating Wind Turbine for Offshore Basin Testing
Authors: de Ridder Erik-Jan , Otto William , Zondervan Gert-Jan , Huijs Fons , Vaz Guilherme 
Published: September 2014

In the last years MARIN has been involved in an increasing number of projects for the offshore wind industry. New techniques in model testing and numerical simulations have been developed in this field. In this paper the development of a scaled-down wind turbine operating on a floating offshore platform, similar to the well-known 5MW NREL wind turbine is discussed.
To simulate the response of a floating wind turbine correctly it is important that the environmental loads due to wind, waves and current are in line with full scale. For dynamic similarity on model scale, Froude scaling laws are used successfully in the Offshore industry for the underwater loads. To be consistent with the underwater loads, the winds loads have to be scaled according to Froude as well. Previous model tests described by Robertson et al [1] showed that a geometrically-scaled turbine generated a lower thrust and power coefficient with a Froude-scaled wind velocity due to the strong Reynolds scale effects on the flow. To improve future model testing, a new scaling method for the wind turbine blades was developed originally by University of Maine, and here improved and applied. In this methodology, the objective is to obtain power and thrust coefficients which are similar to the full-scale turbine in Froude-scaled wind. This is obtained by changing the geometry of the blades in order to provide thrust equality between model and full scale, and can therefore be considered as a “performance scaling”. This method was then used to design and construct a new MARIN Stock Wind Turbine (MSWT) based on the NREL 5MW wind turbine blade, including an active blade pitch control to simulate different blade pitch control systems.
MARIN’s high-quality wind setup in combination with the new model scale stock wind turbine was used for testing the GustoMSC Tri-Floater semi-submersible as presented in Figure 1, including an ECN active blade pitch control algorithm. From the model tests it was concluded that the measured thrust versus wind velocity characteristics of the new MSWT were in line with the full scale prediction and with CFD (Computational Fluid Dynamics) results.
Pressure Fluctuations on a Vertical Wall During Extreme Run-Up Cycles
Authors: Brennan J. , Viotti C. , Dias F. 
Published: September 2014

The run-up of long, strongly nonlinear waves impinging on a vertical barrier can result in remarkable amplification of the far-field amplitude of incoming waves [1,2]. Such an extreme run-up is the result of an evolution process in which long waves experience strong amplification under the action of nonlinear steepening followed by the formation of undular bores, consisting of nonlinearly dispersive wave trains.
Rather than addressing the genesis of such extreme run-ups in any detail, this article describes a specific aspect of the problem; the associated pressure fluctuations at the wall. Numerical computations of the near-wall pressure field show that non-hydrostatic effects can strongly affect the dynamic loads exerted on the wall, and consequently, the high-frequency component of the pressure loads results is significantly enhanced with respect to that of the wave spectrum itself. This observation suggests that also long oceanic waves, at least in some conditions, can be a source of seismic noise.
Assessment of the Surge Effects in a Heaving Point Absorber in the Mediterranean Sea
Authors: Miquel Adrià Moreno , Antonini Alessandro , Archetti Renata , Bozzi Silvia , Passoni Giuseppe 
Published: September 2014

In the present paper, the feasibility of wave electricity production in Italian seas is investigated through the implementation of a variant of the Seabased point absorber WEC. A numerical model of the coupled buoy-generator system is presented, which simulates the behavior of the WEC under different significant wave heights and periods. The WEC scheme is an improvement of the modeling of a three-body device, taking into account several aspects (independence among the bodies, heave and surge) ignored in previous studies for simplification of the scheme.
One WEC composed by three bodies is simulated, with two different hydrodynamic numerical model schemes: a floating buoy and a submerged sphere placed at 25 meters below the water surface. The third body is the translator of the linear generator, which is located at the sea bottom and attached to the submerged sphere by a steel wire.
For the hydrodynamic numerical model, the two bodies are allowed to move independently; heave and surge modes have been taken into account. The first scheme consists in the modeling with only three degrees of freedom, one per body only in the vertical direction (heave) and the other with five degrees of freedom, adding the horizontal component of movement for the buoy and the submerged body (surge). The results are compared with previous results of a WEC modeled as a single body system, with only one degree of freedom along the vertical axis. Preliminary results show that the produced energy in a simplified 1 DoF scheme is higher than results produced by the 3 DoF scheme, and is then approximately equal for the 5 DoF. The power matrixes present similar shapes. So the simplification made by neglecting the surge mode, in order to have a simpler dynamic model, doesn’t give a significant improvement in the capture width and energy production assessment.
CFD Analysis of Waves Over a Submerged Cylinder in Close Proximity of the Free Surface
Authors: Ottens Harald , Pistidda Alessio , van Dijk Radboud 
Published: September 2014

Diffraction programs using potential theory are a quick and effective method in calculating wave forces and ship motions. However in cases where a small layer of water is present on top of a submerged body diffraction calculations overpredict motion and wave force RAOs. This shortcoming of diffraction programs is observed after conducting model tests on a captive submerged cylinder and a free floating SSCV. Unrealistic high wave elevations were predicted by diffraction programs on top of the submerged body. In a previous study a damping lid is implemented [1], to decrease the water elevation to realistic values.
In this study CFD is used to simulate the captive submerged cylinder in regular waves with different wave heights, wave periods and different submerged drafts. In addition irregular waves are used in the simulation matching the wave spectra used in the model tests. The simulations are transient and require high CPU usage, therefore the influence of numerical settings on wave propagation is investigated. Turbulent, laminar and inviscid flow are applied to evaluate which flow phenomena are important. The forces in heave and surge direction are validated with model test data of the captive cylinder. The numerical water elevation on top of the captive cylinder will be used to gain insight in the fluid flow and can be used as a guideline for the use of damping lids in diffraction programs.
This paper will focus on the CFD simulations and the validation with available forces obtained by model tests of the captive submerged cylinder. It will address the use of regular and irregular waves constructing the force RAO for this non-linear phenomenon. Lessons learnt to improve the CFD simulations as well as limitations of constructing RAOs using CFD from an engineering perspective will be addressed as well.
A Novel Approach for Modelling a FPSO Riser Turret Mooring (RTM) System for Mooring Design
Authors: Pistani Fabrizio , Brooker Daniel 
Published: September 2014

The design approach for the analysis of a riser turret mooring system (RTM) connected to a FPSO is presented here. The design was carried out with the use of numerical models developed with Ariane and Orcaflex software packages. Ariane has been used as a screening tool while the model developed with Orcaflex was used for detailed analysis. The succesful validation of the models against existing experimental tests helps to avoid the repetition of a model test campaign for design of new systems. An original solution to overcome the limitations of the mooring software Ariane has been developed and used for mooring analysis.
This paper describes the development of the numerical models highlighting the original features, the validation with the model tests and discusses some of the main results.
Analysis of Octagonal Pile Supporting Offshore Wind Turbines Under Wave Loads
Authors: Lim Serena , Tao Longbin 
Published: September 2014

Offshore wind energy development has gained considerable momentum around the world as wind is stronger and steadier offshore compared to land. This has led to a significant increase in production in recent years, especially offshore wind turbine embedded in shallow waters, such as the recent large scale offshore wind farms in the Northern Europe region. Being at the offshore waters, the wind turbines are subjected to harsh environment. The pile supporting the wind turbine must be reliable and able to withstand such sea condition. It is an important part of the design to study the structural behaviour of the piles under the wave loads.
Due to the significant capital cost associated with the fabrication of the large circular cylinders, a new recommended innovative design to overcome such problem is to substitute the circular cylinder with a vertical monopile of octagonal cross-sectional shape. This paper describes the development of an efficient numerical model for structural analysis of wave interaction with octagonal pile using a modified semi analytical Scaled Boundary Finite Element Method (SBFEM). In contrast to the existing solutions obtained using the traditional methods such as the Finite Element Method (FEM) which typically suffer from high computational cost and the Boundary Element Method (BEM) which faces limitation from fundamental equations and problems with singularities. The most prominent advantage that SBFEM has over the FEM is in terms of the number of elements used for calculation and hence a reduction in computational time. When compared with BEM, the SBFEM does not suffer from computational stability problems.
Universal Crane Model for the Ship Design System E4
Authors: Vorhölter Hendrik , Christiansen Jakob , Hatecke Hannes 
Published: September 2014

For the ship design system E4 a universal crane model was developed. With the help of this model the design of crane vessels and cranes can be harmonised better and lifting operations can be analysed more precisely. The model is able to handle any type of cranes which are used in the shipping and offshore industry and provides the input for every simulations method within E4 which needs to consider crane operations. Special focus was given on keeping a common user interface both for the designer of a crane vessel and the planning engineer for lifting operations independently of the type and functionalities of the crane. Such a universal crane model has not been implemented in any other ship design software until now.
In this article the motivation for the development of the model is described together with the requirements for a universal crane model. The principle of the model explained and its functionality is demonstrated in several examples.
Hydrodynamic Forces due to Oblique Wave and Current Loading on Untrenched Subsea Pipelines
Authors: Green Johnathan , Griffiths Terry , Craddock Chris 
Published: September 2014

A number of oil and gas projects encounter significant costs to achieve subsea pipeline stabilization using present methods. The standard procedure to estimate pipeline stability is to consider the worst combination of amplitude and direction of the current and waves that the pipe will undergo during its operational lifetime. To calculate the hydrodynamic forces a common approach is to consider only the component of the fluid velocity perpendicular to the pipe axis according to the independence principle. The hydrodynamic coefficients are then taken from a case where the fluid flow is perpendicular to the pipe for similar flow characteristics.
A substantial amount of research has been carried out to assess the hydrodynamic forces on pipelines with the current and wave directions collinear and perpendicular to the pipe. However, only limited information is available on pipeline hydrodynamic forces for highly oblique current and wave flow. A Computational Fluid Dynamics (CFD) analysis was carried out to investigate the effect on pipeline hydrodynamic forces for highly oblique collinear and non-collinear current and wave directions. The work was carried out as part of the STABLEpipe JIP (1) (with participation by Woodside, Chevron, The University of Western Australia, and Wood Group Kenny) which aims to achieve a step-change improvement in the approaches to stability design, especially on mobile or erodible sea beds.
Assessment of the Integrity of the PVDF Barrier in Unbonded Flexible Pipes
Authors: Davidson Michelle , Fernando Upul S. , Hall John , O’Donnell Brendon , Latto James , Karabelas George 
Published: September 2014

The polymer barrier is the most important component in unbonded flexible pipe, providing the leak-tight boundary for transporting hydrocarbon medium. Premature failure of the barrier during service can be costly and may lead to disastrous environmental consequences. Design of the barrier for 25 years’ service integrity is therefore a major requirement in the flexible pipe design process. However, the API design code does not give a specific procedure for the design of the barrier and is mainly concerned with the design of other layers in the pipe which are intended to provide integrity to the polymer barrier.
The selection of barrier material depends on many factors including the service temperature/pressure range and pipe bending requirements. Polyvinylidene fluoride (PVDF) is used as a barrier material in cases where high pressure and relatively high temperature applications are involved. However, a hard polymer such as PVDF can be susceptible to crazing and cracking under specific conditions and therefore the use of PVDF in flexible pipe barriers requires critical consideration of the above issues.
This paper discusses the general design requirements of a single layer barrier, and different barriers in relation to static and dynamic applications. The details of a qualification test program performed to establish service integrity of single layer Solef 60512 PVDF barriers is discussed. The unique testing facilities developed to test the integrity of the barrier are presented.
Analysis of End Fitting Barrier Seal Performance in High Pressure Unbonded Flexible Pipes
Authors: Fernando Upul S. , Karabelas George 
Published: September 2014

End fitting is an essential component of flexible pipes enabling their connection between moving structures and pipes to create a complete pipe infrastructure. Designing the end fitting requires careful consideration of many factors including creating an effective barrier seal, termination of all the polymer and metal layers and anchoring armor layers so that the external loads of the pipe are transferred to the connecting structure without disturbing the seal. The most difficult challenge in designing end fittings for ultra-high pressure pipes is creating the necessary barrier sealing performance. In general, the seal needs to perform to approximately twice the design pressure of the pipe so that it can sustain the burst condition of the pipe. This requires the sealing components to be subjected to extreme loading where most of the sealing components are subjected to severe plastic deformation. Understanding seal deformations and quantifying and demonstrating sealing performance are important in the development of a reliable seal. This paper describes a method of evaluating the sealing performance of end fitting seals. Design requirements of end fitting seals are also described.
The barrier seals in end fittings are normally created by swaging a metal seal ring in between the polymer barrier and the body of the fitting. This creates two leak paths, one between the metal ring and the barrier and the other at the metal-to-metal contact interface between the seal ring and the body. Achieving sufficient compression on the polymer barrier and creating sufficient contact pressure over a reasonable distance at the metal-to-metal interface are the key requirements in developing a reliable high pressure barrier seal. During this study, finite element models have been used to evaluate the contact pressure at seal contacts. These results, with a specifically developed leak criteria, have been used to evaluate the sealing performance. A brief description of the models and some specific results are presented. The FE model predictions are compared with the actual contact pressure measurements of a sealing setup.
Influence of Wave Group Characteristics on the Motion of a Semisubmersible in Freak Waves
Authors: Deng Yanfei , Yang Jianmin , Xiao Longfei 
Published: September 2014

In the last few decades, the hydrodynamic performance of offshore structures has been widely studied to ensure their safety as well as to achieve an economical design. However, an increasing number of reported accidents due to rough ocean waves call for in-depth investigations on the loads and motions of offshore structures, particularly the effect of freak waves.
The aim of this paper is to determine the sea conditions that may cause the maximum motion responses of offshore structures, which have a significant effect on the loads of mooring systems because of their tight relationship. As a preliminary step, the response amplitude operators (RAOs) of a semisubmersible platform of 500 meters operating depth are obtained with the frequency-domain analysis method. Subsequently, a series of predetermined extreme wave sequences with different wave group characteristics, such as the maximum crest amplitude and the time lag between successive high waves, are adopted to calculate the hydrodynamic performance of the semisubmersible with mooring systems in time-domain. The paper shows that the maximum motion responses not only depend on the largest wave crest amplitude but also the time lags between successive giant waves. This paper will provide an important reference for future designs which could consider the most dangerous wave environment.