bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of Applicable Codes and Standards for Design of End Bulkheads of Pipe-in-Pipe Systems
Authors: Manouchehri Soheil , Potter Jason
Published: November 2013

Pipe-In-Pipe (PIP) systems are increasingly used where the primary objective is to prevent wax deposition and/or hydrate formation and to achieve a low Overall Heat Transfer Coefficient (OHTC) value. PIP systems are also increasingly considered as an additional protective layer against loss of containment (e.g. in Arctic pipelines) or to withstand the interaction of a third party (e.g. trawl gear impact) in lieu of costly pipeline burial.

At the end of each PIP section, either at a midline connection or end point tie-in, bulkheads are used as a way of transition from a double wall (PIP) system to a single wall (hub in the subsea structure) system. End bulkheads are designed using detailed Finite Element Analysis (FEA) in accordance with more stringent Pressure Vessel Codes (PVC) and manufactured by forging followed by heat treatment and detailed machining to the required dimensions. As the design of end bulkheads does not fall under the Pipeline Codes, a distinction (so called “code break”) may be required on where the governing code changes from the PVC to a Pipeline Code.

This paper firstly discusses the application and validity of internationally known PVCs (ASME BPVC Section VIII Division 2 [1], BS EN 13445 [2], PD 5500 [3]) that can be used in the design of end bulkheads. This is then shown in practice by using an example of a typical end bulkhead, designed to various PVCs. Finally, results are compared and conclusions and recommendations are made.
Study on Relationship Between Countermeasures and Planning Process in Case of Waterfront Redevelopment
Authors: Kaneda Takayuki
Published: November 2013

Planning body may have the tendency to adopt countermeasures such as construction of infrastructures, introduction of an able execution body, and land use control after making most part of plan including goals. It should be noted that planning body must reconsider plan on the basis of adopted countermeasures, because countermeasures and goals are two sides of the same coin at the stage of execution. Such planning process is shown through the study of the planning of the redevelopment of Minato Mirai 21 area, the largest waterfront redevelopment project in Tokyo Metropolis.
The Coupled Motion of Hull Heave and Moonpool Water of Spar Platform
Authors: Liu Liqin , Zhou Bin , Zhang Yongheng
Published: November 2013

This paper studies the heave of Spar platform hull considering the moonpool water motion. The moonpool of Spar platform is a central opening throughout the cylindrical hull and the guide plate is installed at the bottom of it. If the risers in the moonpool are supported by the tensioner at the top, then the mass of the water in the moonpool is comparable to the platform hull mass and the effect of moonpool water on the platform motion is significant. Gupta et al. (2008) studied the effect of moonpool water on the heave of the Spar platform. In their work the added mass and wave loading are calculated by the Morison approach. The Spar platform is large scale structure. In this paper, the wave loading of platform hull is calculated by potential flow theory and the coupled motion of hull heave and moonpool water is studied. It is found that the hull heave motion will be decreased when the moonpool water motion is considered. The hull heave RAO appears two peaks for the large opening area of guide plate, and the higher heave is exhibited when the wave period is near the natural period of moonpool water vertical vibration.
Improving MMP by Co-Injection of Miscible CO2 With Abu Dhabi Crude Oil
Authors: Javid Khalid , Khalifeh Hadil Abu , Belhaj Hadi , Haroun Mohammed
Published: November 2013

Miscible CO2 injection is a method to increase oil production. Combinations of Carbon dioxide with other gases as miscible solvents are emphasized in this paper to improve CO2 miscible injection process. Emphasis is on identifying CO2 solvent mixtures with reduced MMP to achieve miscibility at reasonable injection pressures in Abu Dhabi fields. Two targeted crude oils (Oil 1 and Oil 2) from Abu Dhabi carbonate reservoirs are utilized. The minimum miscibility pressure (MMP) of targeted oils with mixtures of N2, CH4, C2H6, and HC rich gas of varying composition with CO2 injection gas are evaluated through simulation. Cell to Cell and Semi-analytical (key tie lines) methods are applied using CMG simulator. Results show that miscibility is predicted to occur with multiple contact miscibility (MCM): vaporization and/or condensation mechanisms. The increase of C2H6 concentration in the CO2 injected gas reduced MMPs for targeted Oil 1 by 100 psi/10 mol%. However, N2, CH4 and HC rich gas increments in CO2 injected gas increased the MMPs for targeted Oil 1. MMP was observed to be 2300 psi for pure ethane with Oil 1. In addition, MMPs for targeted oils with N2/ C2H6 and N2/ CH4 injected gas mixtures are assessed. This study can open possibilities for future enriching of CO2 and N2 miscible injection to improve miscibility and recovery of oil.
Riser and J-Tube VIV Analysis Using CFD and FSI for Platform Retrofit Application
Authors: Rubinstein David , Campbell Andrew , Pinna Rodney
Published: November 2013

INTECSEA has been supporting a client in designing, modelling and assessing a proposal to add additional riser capacity to an existing platform through spare drill slots in the jacket structure. Traditional empirical analysis indicated that the spans between the guides would be subject to Vortex Induced Vibration (VIV), prompting the use of VIV suppression strakes. Analysis was performed to quantify the effectiveness of strakes and to optimise where they are required to minimize jacket loads and operational maintenance and inspection requirements. The current models for VIV have been developed for pipelines and long dynamic risers. Traditional rigid risers installed into a traditional jacket are not well covered.

Computational Fluid Dynamics (CFD) modelling was undertaken using ANSYS CFX on bare riser sections, along with strakes of various characteristic parameters based on vendor specifications. A range of current conditions were modelled to stimulate the onset of VIV. Validation of the performance against shedding frequency and mesh independence was performed. This work demonstrated the performance of the strakes in reducing cross flow force amplitude as well as the fluctuating component of the in-line force. The frequency of the force response was also shown to be more random and act on a longer timescale than the bare riser. The increase in drag forces was also found to be of the order reported by the vendors contacted as part of this project.

Fluid Structure Interaction (FSI) simulations were performed for the full riser length to better capture the interdependence of the vortex shedding and the motion of the riser by two-way coupling of the CFD and an FEA model built within ANSYS. Simulations also examined the splash zone where only part of the span was submerged. Larger simulations were performed to quantify the effect of damping due to the adjacent spans which have lateral constraints at the guides within the drill slots. This has been a challenging modelling activity as the CFD model is very large and required High Performance Computing (HPC) to run the model in parallel.

The work has shown that the application of strakes is an effective method of addressing VIV phenomena within this application. The FSI simulations have examined the dynamic damping along the full riser length. Further modelling work can be performed to better understand the conservativeness of these mitigation strategies saving operators significant cost and time in installation and operating costs.
Adapting a Linear Potential Theory Solver for the Outer Hull to Account for Fluid Dynamics in Tanks
Authors: Ludvigsen Arild , Pan Zhi Yuan , Gou Peng , Vada Torgeir
Published: November 2013

The linear boundary value problem for the wave dynamics inside a tank is very similar to the solution for the outer hull. Because of this, the boundary value solver for the outer hull can be re-used for the tank. The oscillating hydrostatic pressure in the tank may also be calculated in the same way as for the outer hull. Thereby, the hydrostatic coefficients from the tank can also be obtained from the outer solution.

This makes it, in principle, easy to adapt outer solution computer code to also account for the inner solutions for all the tanks. The procedure is discussed by Newman (2005). We have used it in a different way, isolating the tank solution into more flexible independent sub-runs. This approach provides part-results for the tanks, like added mass and restoring from the tanks. It also has numerical benefits, with the possibility to reuse the calculations for tanks of equal geometrical shape. We have also extended the procedure to account for full tanks without waves and restoring effects.

The linear tank fluid dynamics is programmed into a quite general hydrodynamic frequency domain solver, with the possibility of automatic transferring of local loads to structural (FEM) analysis.

Results for local loads are presented. A simpler method of quasi-static loading in tanks is discussed, with comparison to the present method. Effects on global motions and local pressure coming from the tank dynamics contributions are pointed out, such as the shifted resonance of the vessel and the added mass which differs from rigid masses of the tanks.
Strength and Deformation Capacity of Corroded Pipes: The Joint Industry Project
Authors: Levold Erik , Restelli Andrea , Marchionni Lorenzo , Molinari Caterina , Vitali Luigino
Published: November 2013

Considering the future development for offshore pipelines, moving towards difficult operating condition and deep/ultra-deep water applications, there is the need to understand the failure mechanisms and better quantify the strength and deformation capacity of corroded pipelines considering the relevant failure modes (collapse, local buckling under internal and external pressure, fracture / plastic collapse etc.).

A Joint Industry Project sponsored by ENI E&P and Statoil has been launched with the objective to quantify and assess the strength and deformation capacity of corroded pipes in presence of internal overpressure and axial/bending loading. In this paper:

• The State-of-the-Art on strength and deformation capacity of corroded pipes is presented;

• The full-scale laboratory tests on corroded pipes under bending moment dominated load conditions, performed at C-FER facilities, are shown together with the calibrated ABAQUS FE Model;

• The results of the ABAQUS FEM parametric study are presented.
Evaluation of Forces on Bilge Keels in Oscillating Flow Using CFD
Authors: Yan Hongmei , Constantinides Yiannis , Wu Guangyu , Seah Robert , Oakley Owen
Published: November 2013

The roll motion of a ship or a FPSO can be effectively mitigated by attaching keels along the bilges. Proper structural design of the bilge keels requires good estimates of the hydrodynamic loads acting on them. However, in simplified applications, Morison’s equation may be adopted with constant hydrodynamic coefficients for the force evaluation. Reported bilge keel failures suggest that the understanding of the total loading on the bilge keel is incomplete. In this paper, direct CFD simulations are carried out for bilge keels with added structural members in regular oscillating, prismatic flows. The hydrodynamic loads from CFD are shown to be significantly larger than those used in conventional design approaches. Sensitivity studies are also conducted here to investigate the dependence of the hydrodynamic loads on different factors including bilge keel configurations and FPSO roll velocities.
Drilling Technologies for Offshore Foundation Engineering
Authors: Spagnoli Giovanni , Weixler Leonhard
Published: November 2013

Offshore piles are normally installed by driving using over-water or underwater hammers. However, there are many situations where pile reaches refusal before the installation depth. This paper briefly describes the current offshore foundation practice, the BAUER technology for onshore pile installation by drilling, the BAUER experiences in the offshore foundation and geotechnical fields and a new technology for supporting offshore pile installation when refusal is prematurely reached by means of the Dive Drill.
A Proposed Concept Design Solution Towards Full-Scale Manganese Nodule Recovery
Authors: Santo H. , Hu P. , Agarwal B. , Placidi M. , Zhou J.
Published: November 2013

This paper, a product of an intensive eight-week Lloyd’s Register Educational Trust (LRET) Collegium held during July – September 2012 in Southampton, UK, presents an innovative engineering system concept design for manganese nodule recovery. Issues associated with environmental impacts, such as insufficient or lack of transparent impact studies of any potential full-scale seabed mining, are identified as the key obstacles which could lead to public protest, thus prevent the mining project from taking place. Hence, the proposed system introduces an environmentally friendly solution with the innovative concept of a black box, which performs in-situ nodule-sediment separation and waste discharge, and allows recirculation of waste water. The use of a modularised mining system with small, active hydraulic, crawler-type collectors is proposed to minimise environmental footprint and increase system redundancy. This yields a comparable estimated sediment-to-dry nodule ratio with previous studies in sediment plume impact assessment. The proposed system is a big leap towards a more environmentally friendly solution for achieving (the first) full-scale manganese nodule recovery. Together with the intended small production scale of 0.5 millions dry nodules per year, the proposed system can also be considered as a full-scale experiment or field measurement: a platform for full-scale research concurrently, particularly in the area of environmental impacts. The proposed system, intended to spur more interest in environmental impact studies and to be more transparent to the public, could benefit both industry and research institutes, for the benefit of everybody.
Internal Wave Soliton Passage Simulation During Offloading
Authors: Xu Wei , Li Yile , Voogt Arjan
Published: November 2013

Large amplitude internal wave solitons, generated by interactions between tidal waves and continental shelf breaks, are found commonly in the continuously stratified oceans. Its impact to the FLNG offloading operations, in both side-by-side and dynamically positioning tandem configurations, has been investigated systematically in this paper. The most severe internal wave soliton from a 3-year current field measurement is used as the base case for the study of a generic FLNG offloading during the soliton passage. The MARIN time domain simulation tool, aNySIM, is extended to model the soliton-induced hydrodynamic loads on both FLNG and LNG carrier. Due to the finite speed of advancing soliton fronts, phase differences occur in the resulting current loads on the vessels. The impact of the soliton on offloading operations is evaluated quantitatively by comparing the simulation results with and without soliton in otherwise identical environmental conditions. The maximum amplitude, advancing speed and heading of an internal wave soliton package are varied to examine its sensitivity to the offloading dynamics.
The Use of Surface Appearance in Combination With Charpy Impact Energy to Determine J-Integral Values
Authors: Walters Carey L. , Wallin Kim
Published: November 2013

This paper gives the theoretical basis for a new method of using Charpy data to estimate fracture toughness in the transition region by using both fracture surface appearance and the traditional Charpy energy. Prior research has shown that the Charpy energy and fracture surface appearance can be used to estimate the upper-shelf J-integral [1]. The current paper extends those ideas by using that same information not to estimate upper-shelf Charpy energy, but to estimate the toughness of fracture mechanics specimens at the same temperature.
Effectiveness of Geophysical Methods in Calcareous Harbor Fills
Authors: Brandes Horst G.
Published: November 2013

The effectiveness of electromagnetic (EM), ground penetrating radar (GPR) and seismic refraction (SR) were evaluated by surveying a shallow trench in which a number of objects of varying composition and size were buried. The trench was excavated in granular calcareous fill material. An experienced geophysical contractor was asked to provide blind predictions of object locations using each of the techniques in turn. GPR with a 400 MHz antenna was the most successful, followed by SR and EM surveying. GPR and SR were also carried out at the port of Hilo to investigate complex subsurface conditions.
Comprehensive Downtime Analysis of DP-Assisted Offloading Operation of Spread Moored Platforms in Brazilian Waters
Authors: Corrêa Diego C. , de Oliveira Allan C. , Tannuri Eduardo A. , Sphaier Sergio H.
Published: November 2013

Oil offloading from Spread Mooring System (SMS) FPSO is usually done by means of a dynamically positioned shuttle tanker (DPST) in tandem configuration. The ST receives the oil pumped by the FPSO from a bow or stern offloading station, and the operation may take up to 3 days. In order to minimize the risks associated with the operation, the shuttle tanker (ST) should be kept within a safety zone with respect to the FPSO, which is usually given as a minimum distance between the two ships and an aperture angle from the FPSO centerline. In order to guarantee the tanker position during the whole operation, the operation must be performed with tankers provided with DP (dynamic positioning) systems. Since SMS FPSOs may be not aligned to the environmental forces, keeping the shuttle tanker in position may be a hard task for the DP system, depending on the environmental conditions. There are non-rare situations in which the ST must be disconnected and the operation interrupted.

The present paper applies a methodology based on static calculation of DP capacity for evaluating the downtime of such offloading operation. The three generations of DP tankers applied in Brazilian waters are considered. Santos and Campos Basin long-term (8-year) environmental conditions (current, wind, local-sea and swell) are used in the downtime calculation. The main objective is to provide a quantitative tool to analyze important parameters of the operation, in order to support some redefinitions in the operational procedure adopted by Petrobras. The main parameters are: the angle of the safe green-zone defined from the FPSO centerline, the installed DP power, the necessity of bow and stern offloading stations in the FPSO, among others.

The results indicated that due to the large variation of wave-wind conditions along the year, both offloading stations are indeed necessary, since the ST can avoid the conditions in which it is pushed towards the FPSO. The results also indicated that incrementing the angle that defines the green-zone substantially decreases the offloading downtime. However, such decision also depends on a comprehensive risk analysis, since in that case the ST may be kept in a perpendicular position related to the FPSO. The risk analysis is beyond the scope of the present work. The DP power specified for the ST generations 2 and 3 are shown to be quite adequate, since it is demonstrated that increasing this power will not lead to a substantial reduction in the downtime.
FSI Methodology for Analyzing VIV on Subsea Piping Components With Practical Boundary Conditions
Authors: Gamino Marcus , Abankwa Samuel , Pascali Raresh
Published: November 2013

A general assumption in performing vortex-induced vibration (VIV) analysis of pipeline free spans is both ends of the free span are fixed and/or pinned in order to simplify computational simulations; however, DNV Recommended Practice F105 states that these boundary conditions must adequately represent the pipe-soil interaction and the continuality of the pipeline. A computational methodology is developed to determine the effects of pip-soil interaction at the ends of a free span. Three-dimensional fluid-structure interaction (FSI) simulations are performed by coupling the computational fluid dynamics (CFD) codes from STAR-CCM+ with the finite element analysis (FEA) codes from ABAQUS. These FSI simulations in combination with separate coupled Eulerian-Lagrangian (CEL) simulations are modeled to mimic real word conditions by setting up boundary conditions to factor in the effects of pipe-soil interaction at the ends of the span. These simulations show a mitigation of overall stresses to the free spans; as a result, the integration of pipe-soil interaction in free span assessment may prove cost effective in the prevention of unnecessary corrective action.
Comparison and Synthesis of 2D+T and 3D Predictions of Non-Linear Ship Bow Waves
Authors: Weymouth Gabriel D.
Published: November 2013

2D+T models for the approximate solution of ship divergent waves are of interest because of the orders of magnitude speed-up that they enable. Nonlinear ship bow waves of slender high-speed vessels are investigated using 2D+T and three-dimensional Cartesian-grid simulations using the conservative Volume-of-Fluid and Boundary Data Immersion Methods to model the fluid and solid interfaces. The formulation of the unsteady two-dimensional problem in this framework is detailed and the results are shown to be quantitatively accurate only when the ship is sufficiently slender and moving at high-speed. The class of bow wave; i.e. non-breaking, spilling, or plunging: is correctly predicted by 2D+T but the location of breaking is not. These deficiencies are overcome to some extent using a Physics-Based Learning Model, which supplements the high-speed 2D+T predictions with a limited set of three-dimensional examples to produce accurate quantitative predictions.
Development of an Analysis Code of Rotor-Floater Coupled Response of a Floating Offshore Wind Turbine
Authors: Suzuki Hideyuki , Shibata Hajime , Fujioka Hiroyuki , Hirabayashi Shinichiro , Ishii Kimiko , Kikuchi Hiroki
Published: November 2013

Coupled rotor-floater response analysis is essentially important for the design of Rotor Nacelle Assembly (RNA) and floating support structure of Floating Offshore Wind Turbine (FOWT). The authors have developed an analysis code UTWind for analysis of the coupled structural response. Blades and floater are modeled as frame structure with beam elements. Lumped mass model is use for mooring. Aerodynamic load on blade is calculated by Blade Element Momentum Theory (BEM), and hydrodynamic load is calculated by Hooft’s method, and Morison equation was modified to be applicable to cylindrical element with cross section with two axes of lines symmetry. The equations of motion of rotor, floater and mooring are solved in time domain by weak coupling algorithm. The numerical results by the code were compared with responses measured by experiment in wave and wind-and-wave coexistence field with/without blade pitch control and showed good agreement. Response by negative damping was reproduced by the code and showed good agreement with experiments.
Effect of Drillstring Deflection and Rotary Speed on Annular Frictional Pressure Losses
Authors: Erge Oney , Ozbayoglu Mehmet E. , Miska Stefan Z. , Yu Mengjiao , Takach Nicholas , Saasen Arild , May Roland
Published: November 2013

Keeping the drilling fluid equivalent circulating density in the operating window between the pore and fracture pressure is a challenge, particularly when the gap between these two is narrow, such as in offshore applications. To overcome this challenge, accurate estimation of frictional pressure loss in the annulus is essential, especially for multilateral, extended reach and slim hole drilling applications usually encountered in shale gas and/or oil drilling. A better estimation of frictional pressure losses will provide improved well control, optimized bit hydraulics, a better drilling fluid program and pump selection. Field and experimental measurements showed that pressure loss in the annulus is strongly affected by the pipe rotation and eccentricity.

Eccentricity will not be constant throughout a wellbore, especially in highly inclined and horizontal sections. In an actual wellbore, because of rotation speed and the applied weight, some portion of the drillstring will undergo compression. As a result, variable eccentricity will be encountered. At high compression, the drillstring will buckle, resulting in sinusoidal or helical buckling configurations.

Most of the drilling fluids used today show highly non-Newtonian flow behavior, which can be characterized using the Yield Power Law (YPL). Nevertheless, in the literature, there is limited information and research on YPL fluids flowing through annular geometries with the inner pipe buckled, rotating, and eccentric. Furthermore, there are discrepancies reported between the estimated and measured frictional pressure losses with or without drillstring rotation of YPL fluids, even when the inner pipe is straight.

The major focus of this project is on a horizontal well setup with drillstring under compression, considering the influence of rotation on frictional pressure losses of YPL fluids. The test matrix includes flow through the annulus for various buckling modes with and without rotation of the inner pipe. Sinusoidal, helical and transition from sinusoidal to helical configurations with and without the rotation of the drillstring are investigated. Results show a substantial difference of frictional pressure losses between the non-compressed and compressed drillstring.

The drilling industry has recently been involved in incidents that show the need for critical improvements for evaluating and avoiding risks in oil/gas drilling. The information obtained from this study can be used to improve the control of bottomhole pressures during extended reach, horizontal, managed pressure, offshore and slim hole drilling applications. This will lead to safer and enhanced optimization of drilling operations.
Residual Service Life Prediction of Offshore Concrete Structures With Chloride-Induced Damage: The State of the Art
Authors: Samarakoon S. M. S. M. K. , Ratnayake R. M. Chandima
Published: November 2013

Offshore oil and gas (O&G) production and process facilities (P&PFs) consist of concrete components and structures with steel reinforcement and pre-stressing tendons. They are vulnerable to deterioration due to chloride-induced damage from being exposed to the severe marine environment. The aforementioned deterioration creates significant challenges to the life extension analysis presently required for P&PFs located in the North Sea. Currently, maintenance work has been carried out via in-service inspection and condition monitoring to assure the structural integrity at a pre-specified level of P&PFs. In this context, the knowledge from existing models forms a basis for making quantitative predictions of the remaining service life of structures and components made of concrete. The service life of reinforced concrete structures in relation to reinforcement corrosion is usually modeled considering the initiation period and the corrosion propagation period. The formation of optimal proactive maintenance and repair strategies for corrosion-damaged reinforced concrete (RC) structures is highly dependent on the results of prediction models. The combination of both field (i.e. inspection) and laboratory data with numerical modeling helps the formulation of models for the prediction of the time to pre-defined limit states or to estimate the time for carrying out necessary maintenance and repair. This manuscript provides a review of the available methods for predicting the remaining service life of RC structures in relation to reinforcement corrosion. It also highlights suitable methods for predicting the remaining service life of offshore ageing concrete structures in a severe corrosive environment.
Centrifuge Experiments to Study Extraction of a Deeply Embedded Spudcan Using Top Jetting
Authors: Kohan Omid , Bienen Britta , Cassidy Mark J. , Gaudin Christophe
Published: November 2013

Extracting the spudcan footings of mobile jack-up rigs from the seabed at the end of their operations is challenging when the capacity of the rig to pull is low compared to the extraction resistance of the spudcans. This is particularly the case when the spudcans are deeply embedded in soft clay and subjected to long periods of operation that place load on the foundations and allow for consolidation to occur in the soil. A technical solution used by the offshore industry to overcome spudcan extraction resistance is to use a water jetting system that ejects pressurised water through nozzles on the spudcan face. The aim of using water jetting with nozzles located at the top of the spudcan is to reduce extraction resistance through fracturing and softening of the upper soil. However, the efficiencies of such systems are not known to offshore jack-up operators. Top jetting efficiency is therefore addressed in this paper, which reports a series of physical experiments on jetted spudcan extraction conducted in a geotechnical beam centrifuge. The efficiency of water jetting is reported for extraction from depths of up to three diameters in normally consolidated clay, for different jetting flow rates. The excess pore pressure and maximum breakout force measured reveal insights into the extraction process with top jetting. The maximum extraction resistance is shown to be unaffected by top jetting but relates to the suction developed at the spudcan base, which can be reduced by jetting at the spudcan base (Bienen et al. 2009; Gaudin et al. 2011). Top jetting can, however, reduce the extraction resistance post breakout as indicated by the experimental results of this study.
Numerical Analysis of Cluster and Monopod Suction Bucket Foundation
Authors: Kim Dong-Joon , Choo Yun Wook , Lee Jin-Sun , Kim Dong-Soo , Jee Sung-Hyun , Choi Jaehyung , Lee Man-Soo , Park Yung-Ho
Published: November 2013

Numerical analyses were performed to study the cluster suction bucket foundation performance in comparison with the monopod suction bucket foundation. The possibility of improving the resistance performance of suction bucket foundations by using cluster configuration was studied. Clustered foundations are formed by arranging multiple bucket foundations in relatively short distances among them. A model cluster foundation composed of three individual buckets was configured such that it has the same cross sectional area, length and total bucket weight to a monopod foundation. Results of numerical modeling are presented in the form of load-displacement curves. Vertical, horizontal and horizontal combined with moment load conditions were considered. The results show that the cluster type configuration improved the resistance performance of the foundations under typical loading conditions.
Dynamic Analysis of Offshore Monopile Wind Turbine Including the Effects of Wind-Wave Loading and Soil Properties
Authors: Ong Muk Chen , Li Hui , Leira Bernt J. , Myrhaug Dag
Published: November 2013

An engineering approach to dynamic analysis of an offshore monopile wind turbine is presented in this paper. The wind-wave coupling for shallow water conditions is considered. Different wind, wave and current loads on the wind turbine within the cut-in and cut-off conditions are taken into account. The hydrodynamic loading is computed based on the corresponding sea-states. The interaction between the foundation and the soil is simulated by nonlinear springs, which stiffness properties are obtained from the axial load transfer (t-z) curve, the tip load-displacement (Q-z) curve and the lateral load-deflection (p-y) curve. Three types of soil conditions are considered in the simulations, i.e., 100% sand layer, 50% sand layer (top) and 50% clay layer (bottom), as well as 100% clay layer. For a given current speed, the variations of the static and the dynamic responses of the wind turbine due to the effects of different wind-wave load combinations and soil conditions have been investigated and discussed.
Validation of CFD and Simplified Models With Experimental Data for Multiphase Flow in Bends
Authors: Nennie E. , Belfroid S. P. C. , O’Mahoney T. S. D.
Published: November 2013

In this paper details of the measurement results of the forces on the bends in a 4″ setup are compared to two models. The first model is a simple analytical model and is used to estimate the forces. In the second model, CFD is used. In the experiments only resulting forces, including upstream and downstream bends and mechanical resonance and interaction is measured. The goal of the CFD was to discriminate between flow and mechanics and to evaluate the influence of a flow disturbance as a result of a bend on the force on a downstream second bend.

For the simplified analytical model the amplitudes are underestimated, but the frequency spectra look very reasonable in case of the slug flow regime. The main advantage of the simplified analytical model is that the computational time is in the order of seconds, but the accuracy is still reasonable for the use in an engineering approach of determining the structural integrity of the complete pipe system. For the CFD the shape of the force function is similar to the experiments. The CFD results indicate that the forces on the second downstream bend are also measured on the first upstream bend. The accuracy of the CFD simulation is the advantage of this model, but the computational time is very long, especially if the multiphase flow simulation is coupled to the structural model.
First Order Reliability Analogies of Nonlinear Bending Moments in Ships
Authors: Oberhagemann Jan , Shigunov Vladimir , el Moctar Ould
Published: November 2013

Hydroelasticity codes based on the solution of the Navier-Stokes equations are beneficial for extreme value predictions of hull girder loads. Since direct long-term analyses using these numerical methods are prohibitive due to excessively large required computation times, strategies are sought to reduce the computational effort. An extrapolation approach allows reducing the required simulation duration significantly. Application to hogging bending moments of flexible containerships agrees with Monte-Carlo simulations in random sea state realisations.
Verification of Engineering Modeling Tools for Floating Offshore Wind Turbines
Authors: Duarte Tiago , Tomas David , Matha Denis , Sarmento António , Schuon Frieder
Published: November 2013

This paper presents a verification exercise with three different codes for floating offshore wind turbine modeling: FAST, S4WT and SIMPACK. The comparison showed good agreement in most of the results, and the main differences identified can largely be traced back to the different physical models used by the three simulation softwares. A detailed analysis of the wind turbine loads and motions is also included. FAST offered a greater computational efficiency compared with the other two softwares. Nevertheless, if one is interested in more detailed loads on blades, exact blade deflection predictions in bending and torsion, elastic effects of the floating platform etc., the more detailed codes S4WT and SIMPACK are beneficial.
A Model Experiment of a Free Standing Riser in the Deep-Sea Basin
Authors: Yamamoto Marcio , Masanobu Sotaro , Takano Satoru , Kanada Shigeo , Fujiwara Tomo , Asanuma Takayuki
Published: November 2013

An experiment using a 1/70 reduced scale model of a Free Standing Riser (FSR) was carried in the Deep-Sea Basin of the National Maritime Research Institute in Japan. For instance, the model’s vertical pipe was about 32m long and the jumper was about 8m long. The FSR model had several measurement stations attached along the vertical pipe, subsurface buoy and jumper; and the motion of each station was measured in 3D by the Visual Measurement System. During the experiment, the effects of the jumper’s top end oscillation on the whole system were investigated. In this case, the top oscillation had propagated along the jumper; however the top oscillation had a reduced effect on the dynamics of the subsurface buoy and vertical pipe. In another experimental case, a current was generated in order to investigate the Vortex Induced Motion (VIM) on the FSR’s Subsurface Buoy. The VIM experiment was repeated for two different buoy models (a smooth cylinder and a cylinder with 3-start heli-coidally strakes) and the results were compared. In this article, some of the experimental results are presented and discussed.
Lateral Buckling Response of Subsea HTHP Pipelines Using Finite Element Methods
Authors: Haq M. Masood , Kenny S.
Published: November 2013

Subsea pipelines are subject to load effects from external hydrostatic pressure, internal pressure, operating temperature, ambient temperature and external reactions (e.g. seabed, structural support). These parameters influence the effective axial force that governs the pipeline global buckling response. Other factors, including installation stress, seabed slope, soil type, and embedment depth, can influence the pipe effective force.

Pipelines laid on the seabed surface or with limited embedment may experience lateral buckling. The resultant mode response is a complex function related to the spatial variation in these parameters and kinematic boundary conditions.

In this paper, results from a parameter study, using calibrated numerical modelling procedures, on lateral buckling of subsea pipelines are presented. The parameters included pipe diameter to wall thickness (D/t) ratio, pipe out of straightness (OOS), operating temperature and internal pressure, external pressure associated with the installation depth, and seabed lateral and axial friction properties.
Carbonate Rock Type Matrix RocMat, The Ultimate Rock Properties Catalogue
Authors: Al-Farisi Omar , Belhaj Hadi , Yammahi Fatmah , Al-Shemsi Abdulla , Khemissa Hocine
Published: November 2013

Rock typing is one of the most important steps in reservoir modeling, and it’s the main task in reservoir characterization. In carbonate, the rock typing work that’s been performed during the last two decades had a little progress in term of providing reliable estimation of reservoir behavior. However, the development of Conjunction Rock Properties Convergence, CROPC, a carbonate rock typing concept that provided an important and easy solution to the carbonate rock typing gaps, has a major breakthrough, even though, CROPC methodology was developed to capture the single pore network through the conjunction of Lithology, permeability, capillary pressure and water saturation. Therefore, the need to identify more complex carbonate pore network had led to the initiation of developing the Carbonate Rock Type Matrix RocMat, which will be detailed in this paper, as part of a Master of Science research project. In this novel concept the carbonate rocks were classified into homogeneous, single pore network, and heterogeneous rocks, dual and triple pore network with the utilization of the effective petrophysical properties of permeability, capillary pressure, saturation, porosity and height above free water level, all were classified in a conjunction matrix that honors these properties and at the same time enables generating sub groups as down scaling and estimation for unseen groups with infinite rock complexity capturing, at the same time it enables the ease to lump the groups and generates upscale-groups that make it easier for utilization by the geologist and reservoir engineers to achieve the objective of better reservoir performance prediction, the work was performed and then tested in two carbonate offshore fields data. This RocMat was structured to be the ultimate catalog for carbonate rock types.
Prediction of Travelling Time and Exhaust Gas Emission of Ships on the Northern Sea Route
Authors: Reimer Nils , Duong Quang-Tan
Published: November 2013

In order to simulate the impact of increased shipping activities to the arctic environment for a scenario with decreasing ice extent and ice volume, a simulation tool for ship travelling time was enhanced with regard to the determination of fuel consumption and exhaust emission on the Northern Sea Route (NSR).

The tool was then used to investigate the impact of ships in different periods within the years 2000 and 2007 with various ice conditions.

The transit speed is compared for different periods in the past and present by using ice records from different years together with route parameters and ship data as input for a simulation program. The program is able to calculate the ship resistance in open water and additional components due to wind, waves and ice within a speed range. By including specific propulsion data of the ship, a requested power is obtained for the speed range. The maximum speed is finally interpolated using the maximum available shaft power.

The simulations are carried out for three different ship types with different hull shapes and propulsive power. The results show a significant decrease of travelling time for 2007 compared to 2000. Further in 2007 the season in which transport via the NSR is profitable is clearly extended to the winter months.

In a second work task the program is further developed with respect to the determination of fuel oil consumption and exhaust gas emission. Due to increased resistance during ice breaking, high thrust has to be provided at low speed leading to an off design condition for propulsion arrangements which are optimised for service speed in open water.

It can be found that the resulting actual fuel consumption is closely related to the operation profile of the ship. High values for fuel consumption thereby occur at service speed in ice free water but also at very low speeds in very tough ice conditions. For moderate ice conditions the fuel consumption and related emissions can be lower especially if the ship is forced to slow steaming for safety reasons.
Prediction of the Effects of Fast Passing Vessels on Moored Vessels
Authors: Pinkster J. A. , Keuning J. A.
Published: November 2013

An analysis method to determine the behaviour of a moored ship due to wash waves created by a passing fast vessel has been developed. The method can be used for quantitative assessment of the motions of the moored vessels due to wash waves.

In this paper a short review of the main elements of the computational method is given and comparisons made with results of model tests carried out at MARIN with the concept of a fast passenger ferry and a captive barge representing a moored vessel.

Besides having the possibility to analyse, in the design stage of a fast vessel, the effects on other waterway users, criteria are needed to determine acceptable limits for the motions and accelerations of the moored vessel as caused by the passing vessel. In this paper motion criteria developed based on a comprehensive field study carried out in the Netherlands using the experiences of crew members of moored barges are compared with results of computations of barge motions.
Testing and Characterization of Vulcanized Nitrile Swelling Elastomers
Authors: Moslavac Bojan , Matanovic Davorin , Hrnjak-Murgic Zlata
Published: November 2013

This paper describes preliminary methodology and characterization of the vulcanized nitrile butadiene rubber (NBR) samples submitted to swelling and mechanical testing. Nitrile rubber was used to study swelling processes of swelling packer sealing element. Five different compositions for a rubber vulcanization were used trying to build the best possible combination of components applying different concentrations of each component. Both swelling and mechanical testing were done at the room temperature. Rubber samples swelling was performed in oil acquired from one of Croatian oil fields. The other part of the testing sequence refers to tensile stress-strain tests to the point of break performed on dumbbell samples. Tensile testing was rendered on non-swollen rubber samples using a tensile testing apparatus. From the obtained results it can be seen that swelling process of the nitrile rubber strongly depends on cross-link density.
Experimental Study for SPAR Type Floating Offshore Wind Turbine With Blade-Pitch Control
Authors: Chujo Toshiki , Minami Yoshimasa , Nimura Tadashi , Ishida Shigesuke
Published: November 2013

The experimental proof of the floating wind turbine has been started off Goto Islands in Japan. Furthermore, the project of floating wind farm is afoot off Fukushima Prof. in north eastern part of Japan.

It is essential for realization of the floating wind farm to comprehend its safety, electric generating property and motion in waves and wind.

The scale model experiments are effective to catch the characteristic of floating wind turbines.

Authors have mainly carried out scale model experiments with wind turbine models on SPAR buoy type floaters. The wind turbine models have blade-pitch control mechanism and authors focused attention on the effect of blade-pitch control on both the motion of floater and fluctuation of rotor speed.

In this paper, the results of scale model experiments are discussed from the aspect of motion of floater and the effect of blade-pitch control.
Metocean Data Acquisition, and Live Transmission, for Tidal Array Sites
Authors: Nicholls-Lee Rachel , Csehi Jon
Published: November 2013

With tidal stream energy moving ever closer towards full commercialization, there is a growing requirement for environmental monitoring and acquisition of meteorological data in sites of high flow velocity. Such data is imperative for installation of devices, design of arrays and for through life environmental monitoring of farms.

Previously the typical method of obtaining accurate, live data has been to deploy a separate work vessel equipped with current monitoring equipment wasting fuel, time and money. Conventional buoys are not suitable for use on strong tidal current sites as the drag forces pull the buoy under water when the current speed increases. This work discusses the development of the Mojo Current Buoy, designed to provide tidal current profile and heading data for transmission back to land or ship in extreme tidal locations without submerging. It delivers a live data stream for the assistance of marine operations, and can also be used as a cost effective alternative to vessel or bottom mounted acoustic profilers for metocean data acquisition at tidal array sites. A case study of a recent operation based at the EMEC site, Orkneys, is used to illustrate the capabilities of the buoy.
Evacuation in Ice: Ice Loads on a Lifeboat During Field Trials
Authors: Simões Ré António J. , Veitch Brian
Published: November 2013

Full-scale field trials of a conventional lifeboat in pack ice have yielded insights into the design and operation of evacuation craft in ice. The multi-year trials program used an instrumented lifeboat to investigate design considerations such as powering and propulsion, hull form, maneuvering, ice loads and ergonomics. Operational issues that have been examined include ice management for emergency evacuation, coxswain competence and training. This paper focuses on local ice loads measured on the hull during aggressive operations in pack ice. Field measurements are presented and the implications for design and safe operations are discussed.