bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Aspects of Using Thoria Fuel in SuperCritical Water-Cooled Nuclear Reactors
Authors: Grande Lisa , Villamere Bryan , Rodriguez-Prado Adrianexy , Mikhael Sally , Allison Leyland , Pioro Igor
Published: February 2010

SuperCritical Water-cooled Reactors (SCWRs) are one of six next-generation nuclear-reactor design options under consideration worldwide. These nuclear-reactor design options are included in the major international treaties such as: Generation IV International Forum (GIF) and INternational PROject on innovative nuclear reactors and fuels (INPRO). SCWR coolant is light water, which operates at supercritical pressures and temperatures. Typical SCWR coolant operating parameters are 25 MPa and 350–625°C. These SCWR operating conditions significantly increase the thermal efficiency of a SCW Nuclear Power Plant (NPP) (about 45 – 50%) compared to that of existing NPPs (30 – 35%). Also, SCWRs use significantly higher water parameters than existing water-cooled reactors, because of this they can support hydrogen co-generation. Previous thermal-design fuel-channel option studies for SCWRs have shown that the use of uranium dioxide (UO2) fuel at supercritical water conditions might be unacceptable as the fuel centerline temperature is close to or even exceeds the industry accepted limit of 1850°C. Alternative fuels with a higher thermal conductivity have to be considered. Thoria (ThO2) fuel is a suitable alternative to UO2 due to its higher thermal conductivity. Thoria fuel is beneficial because it complies with the Non-Proliferation Treaty and there are plenty of reserves worldwide. Therefore, ThO2 fuel and its suitability with SCWR use are considered in this paper.
The Water Ingress Mass Analysis on Steam Generator Heat-Exchange Tube Rupture Accident of High Temperature Gas-Cooled Reactor
Authors: Wang Yan , Zheng Yanhua , Li Fu , Shi Lei , Zhou Zhiwei
Published: February 2010

The module high temperature gas-cooled reactor (HTGR) is an advanced reactor with high safety level. The steam generator heat-exchange tube rupture (SGTR) accident (or water ingress accident) is an important and particular accident which will result in water ingress to the primary circuit of reactor. Water ingress may, in turn, result in chemical reaction of graphite fuel and structure with water, causing release of radioactive isotopes and generation of explosive gaseous in large quantity. The analysis of SGTR is significant for verifying the inherent safety characteristics of HTGR. One of the key factors is to estimate the amount of water ingress mass which is used to evaluate the severity of the accident consequence. The 200MWe high temperature gas-cooled reactor, which is designed by the Institute of Nuclear and New Energy Technology of Tsinghua University, is selected as an example to analyze. The accident scenarios of double-ended rupture of both single and two heat-exchange tubes at the inlet and outlet of steam generator are simulated respectively by RETRAN-02. The results show that the amount of water ingress mass is related to the break location, the number of ruptured tubes (or the break size). The greater the number of ruptured tubes or the break size, the larger the amount of water ingress mass. It is important to design the draining pipe line with reasonable diameter, which should be optimized based on economy and safety considerations for preventing large water ingress to the reactor primary circuit, restricting the change rate of mechanical load on SG, and reducing the radioactive isotopes release to the secondary circuit.
Experimental Investigation of a Viscous Surfactant and Surfactant Flooding to Enhance Oil Recovery
Authors: Arjmand Omid , Foroozesh Jalal , Roostaee Ali Reza , Ayatollahi Shahaboddin
Published: February 2010

A chemical Enhanced Oil Recovery (EOR) process receives more attentions nowadays. Crude Terephthalic Acid (CTA) as a chemical compound is used for flooding here as an alternative to the traditional hydrolyzed polyacryl amide (HPAM). Crude Oil samples from an Iranian oil field were used during the flooding tests. Sand packed models using two different sizes of sand mainly 50 and 100 meshes were employed in this investigation. A comparison between water flooding and CTA flooding as a secondary oil recovery process revealed that the recovery was improved by 10% when CTA was used. The effect of various injection rates and different concentration of chemical solutions on the recovery factor have been checked. Besides, experimental results improved the surfactant behavior of the CTA solution in water. Moreover, at tertiary state, Sodium Dodocyl Sulfate (SDS) as an anionic surfactant was flooded. Experiments showed that recovery factor increased by 5% OOIP while using SDS.
Blade Henning Devices for VIV Suppression of Offshore Tubulars
Authors: Lee Li , Allen Don W. , Henning Dean L.
Published: February 2010

This paper discusses a new type of vortex-induced vibration (VIV) suppression devices, the blade Henning device, named after one of the primary inventors, Dean Henning. It consists of four blades, 90-degree apart, on a circular shaped sleeve. Tests of these devices on a flexible cylinder in uniform flows have been conducted. The results indicate that the amount of suppression required with this type of apparatus to effectively mitigate VIV is significantly reduced.
Wave-Induced Liquefaction Around Breakwater Heads
Authors: Ou Jianhua , Jeng Dong-Sheng , Chan Andrew , Vun Pui-Lee
Published: February 2010

In this paper, a poro-elastoplastic model (PORO-WSSI II) is proposed to prediction of wave-induced liquefaction around breakwater heads. Existing models for the wave-induced seabed response around breakwater heads have been limited to poro-elastic soil behaviour and de-coupled oscillatory and residual mechanisms for the rise in excess pore water pressure. The proposed model was reduced to special cases and verified with existing 2D experimental data available and 3D analytical solution in front of a breakwater. With the proposed new model, a parametric study is conducted to investigate the relative differences of the predictions of the wave-induced pore pressure and liquefaction with poro-elastic and poro-elasto-plastic models. With the new model, we further investigate the wave-induced liquefaction in a layered seabed around breakwater heads.
Greater Plutonio Riser Tower Installation: Studies and Lessons Learnt
Authors: Zimmermann Charles-Alexandre , Layrisse Guilhem , de la Cruz Daniel , Gordonnat Jeremy
Published: February 2010

The BP operated Greater Plutonio field development offshore Angola comprises a spread-moored FPSO in 1,300 m water depth, serving as a hub processing the fluids produced from or injected into the subsea wells. The selected riser system is a Hybrid Riser Tower comprising 11 risers bundled around a central structural tubular (Core Pipe), tensioned by a steel Buoyancy Tank at its top and maintained by an anchor base at its bottom. The Riser Tower is fabricated onshore and then towed to the field for final installation in deepwater near the FPSO. Once the Riser Tower installation is completed the risers are connected to the FPSO by means of flexible jumpers and to the flowlines by means of rigid spools. All fabrication and installation work has been performed by Acergy. This paper presents the studies performed to cover all the steps of the installation phase: build-up of the Orcaflex model, miscellaneous studies to determine model and analyses parameters, towing analysis, upending analysis, Buoyancy Tank ballasting and deballasting analyses, and contingency analyses. This paper is mainly focused on the Riser Tower installation but also covers the installation of the Riser Tower anchor and of the flexible jumpers in order to give a complete overview of the operations related to the Riser Tower system. A comparison between computed data and data measured during operations is also presented to support the overall installation analysis methodology. Lessons learned are provided for future improvement of Riser Tower installation covering main challenges such as Riser Tower modeling, weight/buoyancy repartition along the Riser Tower, Buoyancy Tank ballasting adjustment in Lobito bay, fatigue issues during surface and subsurface tow, bending moment issues during upending, etc.
Study on the Characteristics of Temporal and Spatial Variation of Suspended Sediment in the Pearl River Estuary
Authors: Zhang Wei , Yang Mingyuan , Zhang Xiaolin , Dong Peipei
Published: February 2010

The Lingding Estuary is one of the main parts of the whole Pearl River Delta, which lies in the South Sea, China. It is about 60 km wide from Hong Kong in the east to Macao in the west and the water areas are approximately 2110 km2. The process of suspended sediment movement is influenced by many factors, such as the estuarine geometry, tidal range and ravine flows etc.. In this paper, large scale hydrological observations in the Lingding Estuary have been respectively carried out in July, 2003. Based on these data, characteristics of temporal and spatial variation of suspended sediment concentration (SSC) in the Lingding Estuary are studied. The research result shows that SSC changes with the variation of tide current and runoff, the sediment re-suspension is often occurred 1–2 hour following the flood or ebb tide. The maximum turbidity appears near the gauging station V3. In the flood dominant stage, the sediments move towards the mainland, while during the ebb sediments move down.
Stability Analysis of Jetties in Soft Soils Based on Strength Reduction Method
Authors: Xu Qianjun , Zhang Limin
Published: February 2010

This paper presents a stability evaluation of jetties constructed on soft soils for channel protection at Huanghua Port of China, through finite element analysis incorporating strength reduction technique. During construction, shear strengths will increase with the consolidation of soft foundation soils to a great extent. In order to consider this characteristic, the construction process of a jetty-foundation system is simulated by finite element method. The jetty-foundation system is long enough to be regarded as a plane strain problem and is discretized with two-dimensional finite element mesh. In order to implement strength reduction, each node on the mesh is given a temperature. By defining the cohesions and internal friction angles of soils as functions of temperature, the shear strength of the foundation soils can be assigned for each element. The temperature-dependent properties can be used to realize shear strength reduction by changing the nodal temperature in the subsequent analysis. With this technique, the factor of safety of the jetty-foundation system can be achieved in a single simulation process. Repeat trial simulations are avoided.
Numerical Simulation of Sloshing in a Tank, CFD Calculations Against Model Tests
Authors: Iwanowski Bogdan , Lefranc Marc , Wemmenhove Rik
Published: February 2010

Simulation of liquid dynamics in an LNG tank is studied numerically. The applied CFD code solves Navier-Stokes equations and uses an improved Volume of Fluid (iVOF) method to track movement of fluid’s free surface. Relative advantages of using two different fluid models, single-phase (liquid+void) and two-phase (liquid+compressible gas) are discussed, the latter model being capable of simulating bubbles and gas entrapped in liquid. Furthermore, the 1st and 2nd order upwind differencing schemes are used with both physical models leading to a total of four possible approaches to solve the problem. Numerical results are verified against experimental data from large scale (1:10) sloshing experiments of 2D section of an LNG carrier. The CFD vs. experiment comparison is shown for tank filling rates of practical interest, ranging from 10% to 95%, and includes both fluid height and fluid pressure exerted on tank walls. A visual comparison in form of computer animation frames, synchronised with camera-made movies taken during the experiments is included as well. Finally, an exhaustive computational grid convergence study is presented for lower filling rates of the tank.
Geotechnical Centrifuge Modelling Techniques for Submarine Slides
Authors: Boylan N. , Gaudin C. , White D. J. , Randolph M. F. , Schneider J. A.
Published: February 2010

The gradual shift of hydrocarbon developments into deeper waters has presented fresh challenges for offshore geotechnical engineering. Many installations in deep water require export pipelines to shore which can be many hundreds of kilometers in length. These pipelines must negotiate unstable regions of soft seabed around the steep continental shelf and variable terrain including canyons with depths ranging from tens of meters to a several hundred meters. These challenging conditions present potential geohazards for which little understanding has been developed so far. One of the major geohazards is the impact of a submarine landslide on nearby pipelines which could potentially damage the pipeline. Consequently, a Joint Industry Project (JIP) has been initiated at the Centre for Offshore Foundation Systems to improve methods for assessing the potential damage to pipelines and to provide information to assist re-routing of a pipeline to a safer alignment if necessary. This paper presents an overview of the development of specific modeling techniques to (i) trigger a submarine landslide in a geotechnical centrifuge, (ii) measure the strength properties of the slide material before, during, and after the slide failure and (iii) measure the interaction between the runout material and the seabed.
Study on Characteristics and Operating Parameters of Axial Rotating Hydrocyclone
Authors: Xu Yan , Wang Zunce , Lv Fengxia , Li Sen
Published: February 2010

The axial rotation of the hydrocyclone affects its internal flow characteristics and separating effect directly, as some local applications require the static hydrocyclone rotates about its own axis. Based on CFD, velocity distribution in the axial rotating hydrocyclone is studied. It is shown that as the rotation speed increasing, the tangential velocity improves and its gradient reduces in free vortex region observably, while the radial velocity has an incremental trend in the section of the small cone. The laboratory experiments are carried out for the static hydrocyclone of disposal capacity of 4 m3/h at 100r/min ∼ 300r/min. The relationships among rotation speed, flowrate, pressure drop and separated efficiency are achieved, which agree well with the numerical simulation results. The results indicate that the disposal capacity of hydrocyclone subjected to the rotation wall can be more flexible than that with no-rotating wall, the scope of best disposal capacity gradually enlarges with the increase of rotation speed of wall. Appropriate rise of the rotation speed is favor of the separation efficiency at the steady flowrate, however the increase of the flowrate and rotation speed induces the growth of the hydrocyclone’s pressure drop correspondingly to some extent.
Flexible Pipe Curved Collapse Resistance Calculation
Authors: Paumier Laurent , Averbuch Daniel , Felix-Henry Antoine
Published: February 2010

In the design of flexible pipelines for offshore field developments, the determination of the pipe resistance while subjected to external pressure and bending is very important in deepwater and is now required by the ISO and API standards. One of the critical failure modes being associated with this type of loads is the hydrostatic collapse. The collapse value of flexible pipe is calculated with a model validated with over 200 tests performed on all possible pipe constructions. This model has an analytical basis, and has been established in the past, leading to a fast and straightforward use. In order to address the bent collapse failure mode, Technip and IFP have therefore developed and improved over the past few years an analytical calculation model, based on the collapse model for straight pipes. The purpose of this paper is to present this design methodology and its validation. The modelling principles of the collapse calculation of straight flexible pipes are firstly presented, along with the main hypotheses. The adaptation to the case of curved pipes is detailed in the sequel of the paper. Many types of flexible pipe samples have been tested up to collapse both in straight and curved configurations. The results of these tests have been used to validate this model. In the paper, several tests results will be presented and compared with the calculations. This model is effective, of straightforward use, and has been certified by a third party. It allows Technip to optimize the flexible pipe design in particular for ultra-deep water applications, where external pressure resistance is very important.
Offshore Wind Turbine and Substructure Modelling for a Float Over Installation Design
Authors: Cholley Jean-Marc , Cahay M.
Published: February 2010

We can learn from the offshore oil and gas experience for the future offshore wind turbine installation. For the offshore ‘wind farm’ developments, the installation of wind turbines onto preinstalled foundations using the heavy lift vessel method or stabilized vessel is now well established, though, for large units, this requires multiple lifts and hence extensive offshore assembling. As demand for lift vessels increases, their availability to match a future large specific project’s schedule cannot be guaranteed. Consequently, an alternative wind turbine installation vessel design has been developed for not only installing simultaneously two wind turbines in a single piece, but also with a high air gap (up to 70 ft). This paper presents this new design. The new vessel design consists of a catamaran shaped vessel with dimensions that permit it to go around variety of substructures (piles foundation, tripod, concrete foundation or floating substructure) for float-over installation of wind turbines. For the float-over operation, a thorough understanding of dynamic behavior and environmental conditions are necessary to allow the design load to be assessed, with the objective to minimize the risk and maximize the operating sea states. This paper gives a description of how the substructure / Wind turbine / transition piece / floating unit can be modeled. This new vessel design greatly extends the geographical range for offshore wind turbine installation using the float-over method and offers a cost effective alternative to relying on crane vessels.
Model Test and Full Scale Measurements of Whipping on Container Vessels in the North Atlantic
Authors: Storhaug Gaute , Mathisen Jan , Heggelund Svein Erling
Published: February 2010

Ships vibrate due to waves, and these wave induced vibrations can not easily be avoided by moderate changes to the hull lines. The waves may cause the whole hull girder to vibrate due to springing (resonance) and whipping (transient response), which increase the fatigue and extreme loading. Recently this has also become an industry concern. Modern hull monitoring systems in combination with model tests are the best tools to answer the key questions: How important is the wave induced vibrations, and does it have to be included in design? This paper addresses the effect of whipping on the extreme loading. Measurements have been carried out on two container vessels operating in the North Atlantic. An elastic model of the larger vessel has also been tested. Results are obtained at quarter lengths and amidships. From the measurements the increase due to whipping is considerable, even though the wave conditions are not extreme. The full scale measurements and model test show that IACS URS11 rule loads may be exceeded in less than extreme sea states, in particularly amidships and in the aft ship. The IACS UR S11 may need revision for container ship design. MAIB’s report based on the investigation of the MSC Napoli incident (vessel broke in two) also recommends increased requirements for container ship design and further research into the effect of whipping.
Methodology for Disconnect Analysis of CWO Risers in Random Seas
Authors: Grytoyr Guttorm , Rustad Anne Marthine , Sodahl Nils , Bunaes Per Christian
Published: February 2010

The term ‘riser recoil’ refers to the situation when the lower end of a top tensioned riser is released, and the riser is lifted up by the riser tensioner and/or top motion compensator system on the supporting vessel. The elastic energy stored in the riser is then released, and the riser ‘recoils’. This paper focuses on the case of planned disconnect. Recoil of Marine Drilling Risers has been the subject of several research papers over the past two decades. Some examples are listed in references [2] through [7]. Completion and Work Over (CWO) risers are unique in the sense that they may be simultaneously connected to both the riser tensioner system and the top motion compensator system of a drilling vessel. A Marine Drilling riser, on the other hand, is only connected to the riser tensioner system. Typically the riser tensioner system has a stroke of ± 8–9 m, whereas the top motion compensator system has only ± 3.5–4 m. It is imperative that the connector is lifted clear of the subsea structure in order to avoid damage to the equipment after the riser has been disconnected. The operating window for planned disconnect of CWO risers is severely limited by the available stroke of the top motion compensator. One of the purposes of the disconnect analysis is to establish the maximum wave height at which there is still sufficient clearance between the connector and the subsea structure after disconnect. Previous experience has shown that this may be the governing limitation for workover operations. The current industry practice is to use a regular wave approach in the analysis. The wave frequency is varied in order to find the maximum response, and hence one is actually searching for the extreme response, without paying attention to the probability that this will occur. In this paper a new method is presented, where the analysis is based on an irregular wave approach and the Monte Carlo technique, using time-domain simulations. Acceptance criteria are established based on a stochastic analysis, and are based on target levels of probability of exceedance. The results are documented through a case study of a typical CWO riser system connected to a semi-submersible in typical North Sea environmental conditions. The semi-submersible and the CWO riser system are exposed to both regular and irregular waves. Comparison of the resulting allowable wave height indicates that using the approach presented here with irregular waves will give a considerable increase in the operating window, and the resulting operability, compared to a regular wave analysis.
Shoulder Ice Barrier Ice Tank Testing—Part I: Qualitative Description of a Shoulder Ice Barrier-Ice Interaction During Model Tests
Authors: Repetto-Llamazares Ada H. V. , Gu¨rtner Arne , Gudmestad Ove T. , Ho̸yland Knut V.
Published: February 2010

This paper describes qualitatively and through visual observations the ice-sheet interaction with a Shoulder Ice Barrier (SIB) during model tests. The model tests were performed in the Hamburg Ship Model Basin (HSVA) during July 2007. Since the SIB represents a new concept in ice barrier structures, model tests were intended to evaluate the general performance of the SIB. The paper describes seven different experiments where the ice thickness, the ice flexural strength, and the shoulder angle of the SIB are the parameters varied among them. The results are presented in two sections. The first part refers to observations common to all the experiments, where ice failure mode and shoulder performance are given specially attention. The second part describes more into detail the phenomena observed in each particular experiment. The former analysis allows the visual identification of three phases (as mentioned in previous publications), and gives a deeper insight of the characteristics of each phase. The later analysis, on the other hand, allows achieving interesting conclusions about the SIB performance under different ice conditions and with different shoulder inclinations. A comparison between the failure mode observed during the model tests and observations presented in the literature of full scale vertical and sloped structures-ice interaction with rubble accumulation is performed. The similarities found in the study between model and full scale observations lead to suppose that the observed model test behaviour may be expected during ice-SIB interaction in full scale. However, some events that could be associated with problems of the model ice scaling are highlighted. As a conclusion regarding SIB performance, it is shown that the shoulder section, which is the principal innovation of the concept, accomplishes its task satisfactorily and represents a key modification to traditional ice barriers in generating smaller ice pieces and avoiding ice overriding.
Prediction of VIV Response of a Flexible Pipe by Coupling a Viscous Flow Solver and a Beam Finite Element Solver
Authors: Pontaza Juan P. , Menon Raghu G.
Published: February 2010

The paper describes a fluid-structure interaction (FSI) modeling approach to predict the VIV response of a flexible pipe by coupling a three-dimensional viscous incompressible Navier-Stokes solver with a beam finite element solver – in time domain. The flexible pipe is modeled as an Euler-Bernoulli beam subject to instantaneous flow-induced forces and solved using C1 conforming finite element basis functions in space and an unconditionally stable Newmark-type discretization scheme in time. At each time step the instantaneous incremental displacement is fed back to the fluid flow solver, where the position of the pipe is updated to compute the resulting instantaneous flow field and associated flow-induced forces. Numerical predictions from the FSI model are compared to experimental measurements of a flexible pipe subject to uniform free-stream currents.
Sealing Analysis of Metallic Interfaces Applied to Shutdown Ball Valves
Authors: Branda˜o M. O. , Netto T. A.
Published: February 2010

This paper presents rough metallic surface contact analysis focusing on the sealing mechanism in metallic interfaces of subsea shut down ball valves. The work is divided in two parts: initially, the actual rough metallic sealing surface of a ball valve is measured and evaluated by using an atomic force microscope (AFM). The surface is modeled using the finite element method in order to estimate the load to cause the plastic deformation needed for proper sealing. Then a case study is carried out to compare the effectiveness of combined sealing (rubber and metal) and metal-to-metal sealing. Based on the experimental measurements and numerical results, some manufacturing procedures for increasing the reliability of a metal-to-metal sealing in shut-down ball valves are presented.
Determining the Service Life of a Steel Wire Under a Working Load in the Wave Energy Converter (WEC)
Authors: Savin A. , Svensson O. , Stro¨mstedt E. , Bostro¨m C. , Leijon Mats
Published: February 2010

There are different types of energy in nature. Kinetic energy of natural movements like ocean waves is one of them. It is advantageous to convert this energy into a form suitable for use. Ocean waves can play important role in tomorrow’s energy production. At the Swedish Center for Renewable Electric Energy Conversion at Uppsala University, the Wave Energy Converter (WEC) was launched offshore outside the Swedish west coast in March 2006. The WEC consists of the linear generator placed on the sea bed and connected to the buoy via the rope, see Fig.2. Different rope solutions were tested. In May 2008, the steel wire Powerplast (28mm) was connected to the WEC. The steel wire has a shorter service life than other parts of the WEC. The steel wire connects the translator and the buoy. Therefore, the steel wire’s lifetime appears to be very important characteristic for the WEC. It is necessarily to determine the service life of the wire. Aggressive environments reduce the calculated service life which results in corrosion of an ordinary steel wire. A high wave climate and the contact loads can drastically affect wear of the wire. In order to prevent metal-to-metal contact between a steel wire and a funnel, the steel wire was impregnated in a black high density (HD) jacketing compound, that had a good abrasion, scratch resistance and a very good heat deformation resistance. The pulsating nature of waves can cause dramatic transition of the wire from the ductile to brittle fatigue fracture appearance. The residual stresses was also the causes of failures in the wire. The research results and the result from a full-scale experiment of dynamic behavior of a steel wire under a working load in the WEC are considered in this work. The measurements of the dynamic force along the steel wire under a water line were conducted offshore at Lysekil off the Swedish west coast.
Assessment of Trawl Board and Anchor Penetration in Different Soils for Use in Selection of a Burial Depth to Protect Submarine Cables or Pipelines
Authors: Resse´guier Se´bastien , Bendzovski Robert , Stro̸m Pa˚l Johannes , Wathne Harald , Vigsnes Maria , Holme Jan
Published: February 2010

Burial of submarine pipelines, umbilicals and cables has proven to be an efficient measure for protection against trawling and anchoring. Since the 1980s, extensive burying of both existing and new submarine cables has lead to a considerably decrease in the number of failures and accidents. While in the available standards and recommended practice, no particular guidance can be found related to a safe burial depth in different soils, a number of studies have been carried out showing that a burial depth of 0.6m provides good protection against trawling and fishing activities in most soils. In the meantime, a demand has developed for even deeper burial depth, especially in soft soil in order to protect also against light fishing anchors. A review of the available literature has been carried out in order to determine the possible range of penetration of trawl board in different soils and under different conditions. This showed that the penetration remained limited whatever type of trawl gear or type of soil. In addition, calculations have been performed in order to assess the penetration of trawl boards with different sizes, weights and a range of soil strength. The results show a good agreement with the observed data, confirming that the penetration of trawl gear will be very limited in most clays with exception of very soft clay where excessive penetration can be expected. To assess anchor penetration, a software predicting the behaviour of drag embedment anchors during penetration in clay has been used. The maximum expectable penetration for different anchor sizes and soil profiles has been calculated and are presented in this paper. The results from these calculations also show that for most of the soils, the penetration of an anchor from a light fishing boat will be limited.
The Qualification and Continued Evolution of Reeled Steel Catenary Risers
Authors: Gray Fin , Howard Brett , Pieton Alexandra , Gallart Ramon
Published: February 2010

Technip began qualification of reeled Steel Catenary Risers (SCR) back in 1997. Industry had raised concerns at that time over the plastic straining cycles that are intrinsic to the reel lay method and the impact these could have upon the service fatigue life of the girth welds. The qualification programme, therefore, included comparison of reeled welds against virgin welds for a suite of fatigue and mechanical testing including full scale fatigue and fatigue crack growth tests. Reeling was shown to have no discernable impact for the fatigue performance level sought when a controlled SCR fabrication process was adhered to. This provided sufficient confidence that the technology was fit for purpose and led to successful fabrication and installation of the first reeled SCR in 2001. Since then more than 25 have been installed in the Gulf of Mexico, with most projects including full scale weld fatigue test qualification following reeling simulations. This paper includes the following: (a) a summary of the philosophy adopted for qualification, fabrication and installation of a reeled SCR, (b) presentation of the reeled SCR track record and evolution of the technology to include mechanized welding processes (c) a look at ongoing developments targeting even higher fatigue performance, and (d) discussion on the development of fracture mechanics techniques that provide further confidence in the concept and can be used to derive appropriate weld acceptance criteria.
Sailing Performance of a Very Large Mobile Offshore Structure for Wind Power Plant
Authors: Korogi Yuto , Hiramatsu Takurou , Takagi Ken
Published: February 2010

We carry out resistance test and oblique towing tank test with a 1/100 scale model of VLMOS for investigating the effect of interaction among the many struts or between lower hull and struts. We also performed an experiment to test the stability of course keeping in which we imitate the wind drag force and sail force by adding external forces. Finally, we demonstrated the navigation performance of the structure with model sails. These results show that the structure has enough performance of the navigation, although the interaction effect due to vortex occurring at the rear part of strut is not negligible.
Numerical Simulation of Debris Flows
Authors: Liu Ko-Fei , Huang Ming-Chun
Published: February 2010

A numerical program developed for field application is presented in this paper. We use the generalized Julien and Lan (1991) rheological model to simulate debris flows. Due to the derivative discontinuous nature of the constitutive law, flow is separated into plug region and bottom region (with stress greater than yield stress). The program solves the plug flow layer solution first and then corrects the solution with the bottom layer approximation. Numerical scheme with upwind method and central difference in space and Adam-Bashforth 3rd order scheme in time is used for both layers. The scheme is tested against analytical solutions and laboratory experiments with very good results. Application to a field case with more complicated geometry, also achieves good agreement with error less than 5% compared with field measurements. Final example demonstrates how this numerical program is used in a preliminary design.
Push-Over Response of a Jack-Up on Sand of Different Relative Densities
Authors: Bienen Britta , Cassidy Mark J. , Gaudin Christophe
Published: February 2010

On location offshore, jack-up structures are subject to environmental loading from wind, waves and current in addition to self-weight. Over the operational period of the jack-up, the environmental loading on a given site may not be unidirectional along the jack-up’s ‘axis of symmetry’ but may act from different directions and/or be non-collinear (i.e. wind acting from a different direction than waves and current), resulting in complex load paths at the spudcan footings. This paper discusses load paths obtained from experiments on a scaled model jack-up for two different horizontal loading directions and illustrate the implications of spudcan load paths for the overall response of a jack-up to failure. Similar tests were performed at two different relative sand densities, allowing the influence of relative density on jack-up behavior to be investigated. Similitude to the prototype was achieved by conducting the experiments in a geotechnical centrifuge at 200g. The paper concludes with numerical predictions of the experimentally measured response, using a macro-element to model the soil-spudcan interaction coupled to a structural finite element program. The footing macro-element has been developed based on plasticity theory and single footing experiments, but its ability to predict the respective load paths of each of the spudcans in a multi-footing system is demonstrated here. The paper further provides the experimentally measured jack-up push-over capacity and numerical predictions in the context of recommendations of current guidelines. This highlights the requirement of nonlinear elasto-plastic modelling of the load-displacement behavior of the jack-up foundations in order to predict the overall response of the system.
A New Biohydrometallurgical Method for Processing of Deep-Sea Mineral Resources
Authors: Konishi Yasuhiro , Saitoh Norizoh , Ogi Takashi
Published: February 2010

This paper concentrates on the application of a biohydrometallurgical method for processing deep-sea mineral resources. Bioleaching technologies developed for terrestrial sulfide minerals now can be applied for metal extraction from deep-sea hydrothermal sulfides. However, little attention has been given to the bioleaching of terrestrial oxide minerals. A potentially attractive bioleaching system using the Fe(III)-reducing bacterium has recently been proposed for manganese crusts and nodules. Experimental results obtained from these systems demonstrate that bioleaching is an economical and environmentally friendly processing avenue to recover valuable metals from deep-sea mineral resources.
Study on Flow Field Character Around Bypass Crossover Sub in Fracturing Process of Horizontal Wells
Authors: Wang Zunce , Xu Yan , Li Sen , Lv Fengxia , Li Wei
Published: February 2010

Based on Reynolds Stress Model (RSM), numerical simulation of flow field around Bypass Crossover Sub in the fracturing process of horizontal wells is carried out by Computational Fluid Dynamics (CFD) analysis. Distribution rules of axial velocity, tangential velocity and radial velocity of fluid field in calculation region are achieved. Results show that strong vortexes and reverse flow exist at the slots on Bypass Crossover Sub, which brings the impact of the fluid on the wall at certain angle. Impacting velocity and angle at different positions of the wall are studied in detail. A Laser Doppler Anemometer (LDA) is applied to examine the flow field velocity distribution. Experimental results agree well with the numerical simulation results, which prove the validity of turbulence model and computational method. Numerical simulation is carried out at different Length-Breadth ratio of slots on the Bypass Crossover Sub. Effect of the Length-Breadth ratio on the scale of vortexes, speed distributions and flow field near the wall area is discussed. All of these will provide some reference on structural optimization and the analysis of erosion.
Simulation of Water Particle Kinematics in the Near Surface Zone
Authors: Najafian G. , Mohd Zaki N. I. , Aqel G.
Published: February 2010

Linear Random Wave Theory (LRWT) is frequently used to simulate water particle kinematics at different nodes of an offshore structure from a reference surface elevation record. It is, however, well known that wave kinematics calculated from LRWT suffer from unrealistically large high-frequency components in the vicinity of mean water level. To overcome this deficiency, a common industry practice consists of using linear wave theory in conjunction with empirical techniques, such as the Wheeler or the vertical stretching methods, to provide a more realistic representation of the near-surface water particle kinematics. In this paper, a modified version of LRWT is introduced, which, unlike the standard LRWT, does not lead to unrealistically large high-frequency components in the vicinity of mean water level. The proposed method leads to predicted kinematics in the near surface zone which lie between corresponding values from the Wheeler and the vertical stretching methods, respectively.
Wavelet Analysis of VIV Characteristics of Circular Cylinders Under Forced Oscillation
Authors: Ikoma Tomoki , Masuda Koichi , Maeda Hisaaki , Hanazawa Sayaka , Tsumagari Yuki
Published: February 2010

This research considers VIV characteristics of underwater tubing structures such as marine risers, from results of a forced oscillation experiment. The rigid circular cylinder models are used which have draft of 80 cm and 60cm and diameter of 5 or 8 cm are used for the experiment. One or two cylinders are arranged, and then the distance of two cylinders is changed in order to investigate influence of the interval ratio between two cylinders to VIV behaviors. The models are set as cantilever which bend in the cross-flow direction due to VIV, and this rolling serves as VIV. This paper describes results of VIV characteristics with the wavelet transform analysis. From the model experiment, relationship between the orbit pattern of vibration of the model cylinder and a contour pattern of the wavelet is considered. As a result, effectiveness of the wavelet analysis in order to understand VIV detail is given.
Spectrophotometric Determination of Nutrients Using Principal Component Regression
Authors: Arai Rei , Nishiyama Taichi , Nakatani Naoki , Okuno Taketoshi
Published: February 2010

Certain environmental factors such as salinity, dissolved oxygen and chlorophyll concentration can be measured by electric or optical sensors, enabling continuous and automatic measurement with high resolution in time and space. Such measurement is of great importance in the monitoring of marine environments. In order to understand the ecosystem of the sea in detail, the distribution of and changes in nutrient concentrations should be measured in terms of primary production. Generally, since seawater contains high concentrations of chloride, bromide and so on, nutrients must be extracted from these ions. Automatic measurement has therefore proven difficult, and water sampling and chemical analysis in a laboratory are required. This paper proposes a simplified method for measuring nitroxide concentration in seawater using ultraviolet spectrometry and principal component regression (PCR). The present method is shown to be superior to the conventional one since it does not require chemical processing or filtration of seawater.
Study on Drifting Distance and Collision Force of Floating Vessels Run on Apron by Tsunami
Authors: Masuda Koichi , Miyamoto Takujiro , Ikoma Tomoki , Masuda Mitsuhiro
Published: February 2010

The present paper describes the application of the moving particle semi-implicit method to a prediction of drifting distance and collision force of floating vessels run on wharf by tsunami. Effectiveness of the application is verified. Solitary wave have been applied to simulated tsunamis in numerical simulation and to the model experiments. A pontoon type floating body has been used to floating structures in numerical simulations using the MPS method. The present numerical results have been compared with the experimental results and the applicability of MPS method has been discussed. Further, after the running on wharf by tsunami, the characteristics of drifting distance and collision force of floating body on the wharf have been discussed.
Factorial Design of Experiments and Interpretation of Results: An Application to Ice Loads on a Conical Structure
Authors: Trumars Jenny , Lo̸set Sveinung
Published: February 2010

The data for this study is taken from a publication by D. S. Sodhi et al. [1]. The experimental setup in their publication was made in a way which, after some manipulation, allowed it to be treated as a full two-level factorial design with four factors. The effects of the factors; sheet ice thickness, flexural strength, ice-structure friction and relative ice structure velocity are studied. For the mean horizontal response force the conclusion is that there are clear effects for the changes in friction, ice thickness and the interaction of these two factors, the other effects are not readily distinguishable from the noise. For the vertical force the only really clear effect on the force is the ice thickness, and possibly there is an effect from the flexural strength. The only effect on the frequency of the response is the velocity. Studying the results from the analysis it should be kept in mind that the experiment was not originally set up as a factorial design and that the results can be misleading, and the manipulation of the data has lead to the introduction of more noise. There is for example no randomization of the trials to eliminate unmeasured effects on the outcome and this study should be seen as a demonstration of a powerful methodology rather than a strict experimental design.
Hydrodynamics Loads on Two Degree-of-Freedom Cylinder With Uncertain Natural Frequencies Subject to VIV
Authors: Lucor Didier
Published: February 2010

In this numerical study, we build response surfaces of two degree-of-freedom vortex-induced vibrations (VIV) of flexibly mounted cylinders for a wide range of transverse and in-line natural frequencies. We consider both the structure and the flow to be two-dimensional and the structure has a low mass damping. The emphasis is put on the representation of the hydrodynamic loads acting on the cylinder in response to the change in the natural frequencies of the structure. The system is sampled for a wide range of natural frequencies within the synchronization region, totaling 149 two-dimensional flow-structure simulations. The parametric range of the in-line frequency is chosen to be larger than the one of the transverse frequency in order to favor multi-modal responses. No preferred frequencies are emphasized within the intervals of study. The fully spectral numerical approach relies on a stochastic collocation method coupled to a spectral element-based deterministic solver.
Effect of Weld Toe Burr Grinding on Fatigue Strength of Transverse Welded Specimens Made From DH36 Steel
Authors: Polezhayeva Helena , Kang Joong-Kyoo , Heo Joo-Ho , Kim Kwang-Seok
Published: February 2010

The effect of weld toe grinding on fatigue life of welded joint has been studied by a number of investigators who have established that improvement factor on fatigue life is greater for higher tensile steels as compared with mild steels [1]. To establish the effect of weld toe grinding on the fatigue strength of joints made from DH36 steel, transverse welded specimens were tested under constant amplitude loading. This work was carried out by DAEWOO Shipbuilding and Marine Engineering Co. within Lloyds Register/DSME Joint Project. It was shown that the improvement factor on fatigue strength due to weld toe burr grinding for DH36 steel is above 1.5 for high cycle fatigue range.
Development of a Fish Behaviour Model in Coastal Sea
Authors: Hakuta Keiichiro , Tabeta Shigeru
Published: February 2010

The evaluation of the behaviours of fish which stand on higher levels of food-web is important from the viewpoint of the resource management or other environmental impacts. Especially for the adult fish which can swim against the currents of circumference, considering the migration effects in the model is quite significant. In the present study, a fish model is developed which considers the migration effect by modeling the preference for the environmental factors. As the target fish of modeling, Pagrus major is chosen because it is one of the representative species due to its high resource value. In the model, the direction of the fish movement is determined by the preference strength for the environmental factors such as water temperature, dissolved oxygen, prey density, and so on. The model is coupled with a hydrodynamic model and a lower-trophic ecosystem model which predict physical environment and water quality of the target area. Numerical simulations are carried out to reproduce the spatial distribution and seasonal variations of ecosystem in east Seto Inland Sea. As a result of the simulations, it is clarified that the both water temperature and prey density have large influence on migration and distribution of Pagrus major.