bluuebunny/crossref_metadata_2025 huggingface dataset:
Energy Efficiency in Thermally Assisted Machining of Titanium Alloy: A Numerical Study
Authors: Ma Jianfeng , Ge Xianchen , Lei Shuting
Published: November 2013

This study investigates the energy utilization and efficiency in thermally assisted machining (TEM) of a titanium alloy using numerical simulation. AdvantEdge FEM is used to conduct the simulation of orthogonal machining of the workpiece. Thermal boundary conditions are specified to approximate laser preheating of the workpiece material. The effects of operating conditions (preheat temperature, cutting speed, depth of cut, and rake angle) on mechanical cutting energy, preheat energy, and energy efficiency are investigated. The results show that preheating the workpiece reduces the cutting energy but increases the total energy in TEM. There is significant potential to maximize total energy efficiency in TEM by optimal design of heating strategies and machining conditions.
Analysis of 1D Abrasive Vibratory Finishing Using Acoustic Emission
Authors: Prakasam Pradeep Kumar , Subbiah Sathyan
Published: November 2013

Acoustic emission (AE) is a widely used non-destructive method for monitoring and control of machining processes. Vibratory finishing is a surface modification process used for polishing, deburring and finishing of components (aerospace, automotive and other industries). The polishing action takes place due to the action of abrasive particles called media on the components subjected to finishing. The media motion is complex and involves a combination of normal and oblique impacts, scratching and rolling. This work deals with the characterization of basic types of media contact occurring in the vibratory finishing process using acoustic emission signals. A novel one dimensional vibratory simulator was developed for this purpose using a tribometer setup. The one dimensional simulator was used to differentiate between the normal and scratching types of media contact and corresponding AE signals were measured. The preliminary results shows that the AE signals obtained for normal and scratching type of contacts are different. In addition to this, AE signals were used to characterize the amount of media.
Characterization of Vacuum Brazing of Ti6Al4V and Alumina With Cu-Ag Brazing Alloy via Substrate-Induced Reactive Mechanism
Authors: Beeranur Ravikumar , Waghmare Kiran K. , Singh Ramesh K.
Published: November 2013

Brazing of ceramic and metal components is an emerging manufacturing technology in which a furnace or a heat source is used to join the substrates using a brazing filler material. Brazing of ceramic and metal has received considerable attention in the field of nuclear reactor, aerospace, automobile, medical and electrical engineering. A brazing alloy can either be a conventional brazing alloy which requires the ceramic surface to be metallized or an active brazing alloy which does not require metallization. A sound interfacial adhesive bond is formed during the process. The typical active elements required in the brazing alloy for bonding of alumina are Ti and Zr. It is expected that since Ti is present in Ti6Al4V, a copper-silver alloy (Cusil™) without an active element can be used for brazing. The Ti substrate itself could provide the reactive element because of dissolution. Vacuum brazing of alumina and titanium with Cusil sheet has been carried out to analyze the characteristics of the joint. Behavior of the joint under different temperature conditions has been studied by thermal cycling of the joint. Uniformity of the joints is confirmed by observing the Scanning electron microscope (SEM) images. The elements and phases present in the joint interface are observed by energy dispersive spectroscopy (EDX) and X-ray diffraction (XRD) analyses. The maximum shear strength obtained in the brazedTi6Al4V/Cusil sheet/alumina joint was 102MPa and the average shear stress was found to be 70±3 MPa. The micro-Vickers hardness test showed that the micro hardness of the interface was lower than the substrates.
A Parametric Analysis on Micro-Drilling Process With Nanofluid Minimum Quantity Lubrication
Authors: Nam Jung Soo , Kim Dae Hoon , Lee Sang Won
Published: November 2013

This paper presents a parametric analysis on microdrilling process using nanofluid minimum quantity lubrication (MQL). In this paper, the effects of several machining parameters such as a feed rate, rotational speed and drill diameter on micro drilling performances are investigated under various lubrication conditions — compressed air lubrication, pure MQL and nanofluid MQL. For nanofluid MQL, nanodiamond particles are used with the volumetric concentration of 4 %. A series of microdrilling experiments are carried out in the miniaturized machine tool system. The experimental results show the nanofluid MQL can be effective for reducing average drilling torques and thrust forces, in particular, at relatively low feed rate (10 mm/min) and low spindle speed (30,000 RPM) in the case using the drill with small diameter (0.1 mm). Meanwhile, in the case using the drill with large diameter (0.5 mm), the nanofluid MQL may not be effective for reducing average torques and thrust forces.
Study of Biobased Shape Memory Polylactic Acid/Thermoplastic Polyurethane (PLA/TPU) Blends
Authors: Jing Xin , Mi Hao-Yang , Turng Lih-Sheng , Peng Xiang-Fang
Published: November 2013

This paper presents the development of shape-memory polymers (SMPs) based on polylactic acid (PLA) and thermoplastic polyurethane (TPU) blends. PLA was melt blended with TPU at weight ratios of 20, 30, and 40%, and then injection molded and hot compressed into permanent shapes. Unlike most of the existing SMPs, all three PLA/TPU blends could be formed (via bending, folding, compression, stretching, etc.) into temporary shapes at room temperature without an extra heating step. Upon heating to above the glass transition temperature of PLA (at 70 °C), the deformed parts regained their original shapes quickly. Differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) tests showed that PLA and TPU were immiscible. The dynamic mechanical analyzer (DMA) data and the mechanical tests, including tensile, compression, and flexural tests, showed that the PLA/TPU with the 80/20 weight ratio had the best shape-memory properties, even if it was somewhat brittle. The 70/30 PLA/TPU blend had the best combination of shape recovery and mechanical properties.
Evaluation of Fiber Orientation Prediction of Moldflow Using an Injection Molded IP Panel
Authors: Sun Xianjun , Gan Yuan , Lasecki John , Zeng Danielle , Qi Li , Li Lu , Webb Jeff , Tao Jie
Published: November 2013

The fiber orientation distribution is one of the important microstructural variables for thermoplastic composites reinforced with discontinuous fibers. In this article, Moldflow is used to predict the fiber orientation distribution in an automotive component. Image analysis by MATLAB is adopted to validate the simulated results after taking pictures of fibers by X-ray CT. It is shown that the Moldflow predicts the average distribution in direction of the thickness accurately, with predicted eigenvalue of the orientation tensor within 5% of that measured. However, it failed to capture the change of principal eigenvalue in thickness direction.
Nonlinear Sloshing in a Spherical Tank
Authors: Faltinsen Odd M. , Timokha Alexander N.
Published: November 2013

Steady-state resonant sloshing in a spherical rigid tank due to horizontal harmonic excitations at the lowest natural frequency is classified by combining the nonlinear multimodal method with the Moiseev-Narimanov asymptotics. The theoretical results are validated by comparison with experiments of Sumner & Stofan (1963) and other already published model tests. A good agreement is found for the depth-to-tank radius ratios 0.2 ≤ h ≲ 1 but, when 1 ≲ h ≲ 2, secondary resonance and splashing limits the applicability of the constructed weakly-nonlinear modal theory.
Loads due to First Year Ice Ridges on a Vertical Cylinder
Authors: Molyneux David , Spencer Don , Liu Lei
Published: November 2013

This paper presents some predictions of ice ridge loads on a vertical cylinder, based on model experiments, analytical methods, and numerical simulations. The experiment program involved the interaction of a vertical cylinder with two unconsolidated ice ridges. Each ridge was nominally 1.9 m wide with a keel 0.5 m deep. The nominal scale used for the experiment was 1:30. The analytical methods included Dolgopolov, Mellor, Croasdale & Cammaert, and ISO19906. The numerical simulations were carried out using a discrete element computer code, named DECICE. The paper compared the results of model experiments, analytical methods and numerical simulations.
Ocean Power Generator Using Flexible Piezoelectric Device
Authors: Mutsuda Hidemi , Watanabe Ryuta , Azuma Shota , Tanaka Yoshikazu , Doi Yasuaki
Published: November 2013

We have developed a way of harvesting electrical energy from ocean power, e.g. tide, current wave, breaking wave and vortex, using a Flexible PiezoElectric Device (FPED) consisting of polyvinyledene fluoride (PVDF) and elastic material such as rubber, silicon and resin. The proposed FPED has a multi-layered structure with a distance δ between FPEDs located away from centerline of the FPED. When the FPED can be easily deformed by ocean power, the PVDF laminated in the FPED can be expanded and compressed and then the internal strain energy can be stored in the FPED. The electric power is generated when the electric polarization occurs in the PVDF.

In this study, we have proposed an ocean power generator of EFHAS (Elastic Floating unit with HAnging Structures) consisting of floating unit and hanging unit using the FPEDs to obtain electric power from ocean energy. We investigated a structure of the EFHAS and also examined characteristics of motion and electric performance of the EFHAS (1/50–1/75 scale model. We made clear that the EFHAS could be useful as ocean power generator.
Map of Passive Turbulence Control to Flow-Induced Motions for a Circular Cylinder at 30,000<Re<120,000: Sensitivity to Zone Covering
Authors: Park Hongrae , Bernitsas Michael M. , Chang Che-Chun
Published: November 2013

Passive turbulence control (PTC) in the form of two straight roughness strips with variable width, and thickness about equal to the boundary layer thickness, is used to modify the flow-induced motions (FIM) of a rigid circular cylinder. The cylinder is supported by two end-springs and the flow is in the TrSL3, high-lift, regime. The PTC-to-FIM Map, developed in previous work, revealed zones of weak suppression, strong suppression, hard galloping, and soft galloping. In this paper the sensitivity of the PTC-to-FIM Map to: (a) the width of PTC covering, (b) PTC covering a single or multiple zones, (c) PTC being straight or staggered is studied experimentally. Experiments are conducted in the Low Turbulence Free Surface Water Channel of the University of Michigan. Fixed parameters are: cylinder diameter D = 8.89cm, m* = 1.725, spring stiffness K = 763N/m, aspect ratio l/D = 10.29, and damping ratio ζ = 0.019. Variable parameters are: circumferential PTC location αPTC ∈ [0°−180°], Reynolds number Re ∈ [30,000–120,000], flow velocity U ∈ [0.36m/s–1.45m/s]. Measured quantities are: amplitude ratio A/D, frequency ratio fosc/fn,w, and synchronization range. As long as the roughness distribution is limited to remain within a zone, the width of the strips does not affect the FIM response. When multiple zones are covered, the strong suppression zone dominates the FIM.
Polar Lows and Their Implications on Marine Operations: Survivability Criteria
Authors: Pakkan Meric , Heng David , Gudmestad Ove Tobias
Published: November 2013

The oil resource potential in the Arctic/sub-Arctic regions is estimated to be as high as that 25% of the world’s yet-to-be-found. Nevertheless, operating in above-mentioned regions is more complicated and expensive than the ones in the North Sea. One of the most important aspects to consider in operating in these Arctic regions is the presence of polar lows and arctic fronts and storms. These extreme events and implications of them on the marine operations were the main focus of this study.

While the maximum polar low-sourced wind speeds for 10-, 20- and 100-year return periods are estimated to be 55.37, 60.93 and 73.52 knots, the maximum polar low-sourced wave heights for 10-, 20- and 100-year return periods are calculated as 5.71, 6.66 and 8.82 meters, respectively.

It is found out that polar lows weather conditions do not normally represent design values (survival conditions); however, they represent operational limitations.

• We conclude that operations lasting longer than 72 hours shall be designed for a rougher weather than the polar lows lead to (survival mode).

• For operations of duration less than 72 hours, the weather forecast is crucial and it must also be possible to abort the operation within a short period if one is close to a polar weather front as a polar low may appear very quickly.
Influence of Axial Boundary Conditions on Free Spanning Pipeline Natural Frequencies
Authors: Forbes Gareth L. , Reda Ahmed M.
Published: November 2013

The effect of axial restraint (boundary conditions) on the natural frequency of a free spanning pipeline is examined in this paper. Theoretical calculation of the natural frequency of a straight pipeline with simple boundary conditions is a trivial task with exact solutions being available. A pipeline lying on the seabed however is neither completely straight and the interaction with the soil at the span shoulders create more complex boundary conditions. DNV-RP-F105 provides guidance on the calculation of free span boundary conditions with these increased complexities. The DNV recommended practice does not however take into account the effect of the axial restraint on the natural frequency. Results are presented in this paper for a range of axial stiffness combined with span out of straightness for a free spanning pipeline. The results presented show that the effect of axial restraint for moderately out of straight free spans can cause significant deviation in the calculation of the span natural frequency.
Prediction of Water Wave Propagation Using Computational Fluid Dynamics
Authors: Javanmardi Mohammadreza , Binns Jonathan , Thomas Giles , Renilson Martin R.
Published: November 2013

In this study the influence of grid effects on free surface deformations behind a ship-like moving vessel were investigated. To determine the influence of grid effects on the water wave propagation, various grid domains with different quality parameters were produced. Simulations were conducted for a moving pressure source and the free surface around the moving body captured. Then three-dimensional numerical results for different grids, in both the near and far field, were compared with experimental data over a range of speeds. The experimental data were obtained using tank tests on a pressure source model at the Australian Maritime College. Wave probes at different lateral distances captured the generated wave parameters. The study revealed that the results of numerical simulation of water wave propagation depend on the grid parameters and geometrical mesh quality.
Influence of Ocean Transport on the Design of Onshore and Offshore Constructions, Modules, Topsides, Jackets and Towage on FPSO Design
Authors: Bos A. J. , Ligterink T. M.
Published: November 2013

Oil and gas installations both onshore as well as offshore are often built in modules and components on a different location than where those facilities are commissioned. Although stress and fatigue damage have proven to be significant on these structures during ocean transport, ocean transportation is often not adequately accounted for during design. Prior to arrival on its final destination, constructions are exposed to severe motions when carried on a modules carrier, a general purpose vessel or towed by 1 or more ocean tugs. The authors argue that calculations on the significance and effect of these motions should be based on proper motion response calculations instead of currently used ‘rules of thumb’. Especially regarding the continuing growth of the size of these carriers and the weight of the structures which both increase the negative effect of sea behavior and affects the loads on the constructions. This article aims to explain the importance of design for transport during the design-phase of these onshore and offshore structures. A distinction is made between structures transported aboard a barge, semi-submersible or general purpose vessel and floating structures transported through a ‘wet-tow’ operation.
Wave Power Extraction by an Oscillating Wave Surge Converter in Random Seas
Authors: Sarkar Dripta , Renzi Emiliano , Dias Frederic
Published: November 2013

This paper investigates the behaviour of a bottom hinged flap-type wave energy converter (WEC), namely the Oscillating Wave Surge Converter (OWSC), in random seas. The semi-analytical model of Renzi and Dias (2013b) for an OWSC in the open ocean is considered to analyze the performance of the device in random incident waves. The modelling is performed within the framework of a linear potential flow theory, by means of Green’s integral theorem. The resultant hypersingular integral equation for the velocity potential obtained from the above formulation is solved using a series expansion in terms of Chebyshev polynomials of the second kind.

The behaviour of the device is investigated for six different sea states, generally representative of the wave climate in the North Atlantic Ocean at the European Marine Energy Centre test site. A Bretschneider spectrum is considered in order to reproduce the sea climate. The analysis is made for sea states where the spectral energy contribution from large periods, which cause excitation of body resonance of the flap — not modelled by the linear theory — is almost negligible. The power take-off damping is optimised for each individual sea state to calculate the captured power.

The investigation is undertaken for two flaps of different widths, resembling the Oyster1 and the new Oyster800 version of the Oyster WEC, respectively. Comparison is made between the performances of the two converters. The effect of varying the width and the characteristic parameters of the flap on the capture factor in random seas is then discussed.

The results of the analysis show that the performance of the device is fairly consistent for the sea states considered. Also an enhancement in the overall average capture factor is shown for the latest version of the wave energy conversion device.
Energy Extraction by Flexible Flapping Twin Wing
Authors: Liu Wendi , Xiao Qing
Published: November 2013

The present study aims to investigate how the flexure of oscillating wings affect their hydrodynamic performance and tidal energy extraction efficiency based on their flapping motions. To achieve this goal, a numerical simulation is carried out by solving a low Mach number compressible Navier-Stokes equation for a parallel arranged twin wing system. Simulation covers a wide range of flapping frequency, various effective angles of attack, the degree of flexure and the gap between two wings. Our results indicate the improved energy efficiency with the use of flexible blade as compared to its rigid counterpart. This becomes more significant especially at high oscillating frequency.
Design for Arctic Conditions: Safety and Performance Issues
Authors: Barabadi Abbas , Naseri Masoud , Ratnayake R. M. Chandima
Published: November 2013

The harsh climate conditions and vulnerability of the Arctic wilderness can both heighten the risk related to HSE (human, safety and environment) and limit the effectiveness of any activities which are carried out to control such risks. To manage and control these risks, it is vital to reduce the probability of failure of critical components in the corresponding industrial setting. In order to accomplish the aforementioned, it is essential to have an accurate prediction of failure characteristics (e.g. failure modes, time to failure and failure mechanisms) and the consequence of failure which can be taken into consideration during the design phase. It is possible to gather such information by means of an effective risk and dependability analysis.

However, in practice, conducting a dependability and risk analysis is a challenging process for an industrial setting, such as that which is functioning in the Norwegian Arctic. This is mainly due to the lack of historical data about possible activities which are unique to the region. Hence, it is paramount to develop a methodology to facilitate the analysis, using the available data experience and technological solutions which can be retrieved from similar or more challenging situations as a reference to improve the robustness of the current design. This paper reviews the main technical and technological challenges of the operations in the Arctic region. Then, it provides a methodology to take risk and dependability analysis for Arctic conditions into consideration in the design phase. This methodology is demonstrated by a case study for design in the Barents Sea based on the available data collected in the North Sea and the Norwegian Sea.
Probabilistic Selection of Ship-Ship Collision Scenarios
Authors: Youssef Samy A. M. , Paik Jeom K. , Kim Yang Seop , Kim Min Soo , Cheng Fai
Published: November 2013

Within the framework of quantitative risk assessment and management in the design stage, it is essential to select relevant sets of accidental scenarios, while a huge number of possible scenarios are obvious. The current industry practices are likely based on prescriptive approaches for the most unfavorable accidental scenarios. However, these approaches are often inadequate for obvious reasons because they may result in too large values of design loads in some cases but they may underestimate design loads in other cases. In the present study, an innovative method using probabilistic approaches is suggested to select relevant sets of ship-ship collision accident scenarios which represent all possible ones. Historical database for each of individual collision parameters which is dealt with as a random variable have been collated and are analyzed by statistical methods to characterize the probability density distributions. A sampling technique is then applied to select collision scenarios. Applied examples to a double hull oil tanker are presented to demonstrate the applicability of the developed method.
Evaluation of Moving Capability of Crawler Driven ROV Considering Cable Tension
Authors: Katsui Tokihiro , Inoue Tomoya , Akashi Masanari
Published: November 2013

A ROV (Remotely Operated Vehicle) which has a crawler based driving system is considered to be one of the appropriate underwater vehicles for seafloor exploration or seabed resources development [1][2][3][4][5][6][7]. The crawler driven ROV is able to move on sea floor, stay on a fixed sea bottom location and is capable to do heavy works such as digging the seafloor. In order to utilize those capabilities, it is important to know the fundamental moving capability of crawler driven ROV. According to the previous investigations [8][9], the crawler driven ROVs are easy to run in bow-up attitude in some running conditions due to the buoyancy and the hydrodynamic forces acting on the ROV. This irregular running sometimes causes a turning over. Therefore, we have to know the restrictions on the design parameters of the ROV not to run in bow-up attitude to design the ROV. The authors have been investigating the moving capability of crawler driven ROV and showed a method to estimate the restrictions of design parameters to avoid the bow-up running, which is called normal running condition [10][11][12][13]. This method is based on a simple dynamic model which considers the forces acting on ROV as concentrated loads; those are gravity, buoyancy, reaction from the ground, thrust and hydrodynamic drag. The loading position of ground reaction in steady running is obtained from the balance condition of forces. We consider that the loading point of ground reaction should be inside between the fore and rear wheels for the normal running. This constrained condition indicates the relation between gravity and buoyancy center locations for the normal run of ROV under the given body geometry, weight, displacement and running speed. This method estimates the ROV’s running capability in acceptable accuracy compared with the model experiments. However, this method does not consider the tension of the cable which is connected to the ROV. As you can easily imagine, the cable tension has a big influence on the movable area of the ROV. If the ROV keeps going forward, it will turn over due to the tension of the cable at a certain point. We must know the movable area of the crawler driven ROV for the operation planning. The present study shows a method to estimate the movable area of the crawler driven ROV under the restriction of the cable by extending the previous method to estimate the normal running condition.
Calculation of Wave Forces on Cylindrical Piles Using a 3D Numerical Wave Tank
Authors: Kamath Arun , Bihs Hans , Arntsen Øivind A.
Published: November 2013

Offshore constructions generally include a large number of vertical cylinders in the support structure. The calculation of wave forces on a vertical cylinder and hydrodynamic effects on it in the presence of neighbouring cylinders is of practical interest. In this paper, a 3D numerical model is used to calculate wave forces on bottom fixed cylindrical piles. Two cases are considered in this study: a single cylinder and a pair of tandem cylinders. A scenario with multiple cylindrical structures in close proximity introduces complex wave-structure interactions and would be of great interest to observe this in detail in a three-dimensional simulation. The wave force exerted on a cylindrical pile is numerically calculated by integrating the pressure and the wall shear stress around the surface of the cylinder. In the case of the single cylinder, the force calculated by the model is compared to the force predicted by the Morison formula and MacCamy-Fuchs theory. In the second case, the pair of cylinders is aligned in the direction of the incoming waves. The numerically calculated inline wave force on each cylinder is compared to the analytical solution for this setup and a good agreement is seen.

The Reynolds-Averaged Navier-Stokes equations are used as the governing equations for the fluid flow in the numerical model. The convective terms are discretized using a 5th-order conservative finite difference WENO scheme. A 3rd-order accurate TVD Range-Kutta scheme is used for time discretization. Chorin’s projection method is used to discretize the pressure. The Poisson equation for pressure is solved using a preconditioned BiCGStab algorithm. The level set method is used to obtain a sharp representation of the free water surface. Turbulence in the flow is simulated using the k-ω model. The numerical model is adapted to parallel processing using the MPI library to improve the computing performance of the code.
Risk and Reliability Analyses for Innovative LNG Offshore Floating Units
Authors: Benyessaad Olivier , Ruf Diane
Published: November 2013

The development of the Liquefied Natural Gas (LNG) offshore industry is viewed as a major improvement in the exploitation of the world’s energy resources. Most energy analysts agree that significant increases in Natural Gas (NG) demand is expected in the next decades due to relatively low prices and an important gas quantity worldwide. In order to develop the use of this resource, many innovative offshore floating installations have been developed and are currently deployed all over the world. However, hazards linked to LNG and due to hydrocarbon releases are not always so well understood or controlled. Thus, in order to quantify and understand these risks associated to LNG treatment or containment as well as their consequences, a number of different types of risk and reliability engineering techniques can be used at different stages of the project. The following will present specific analyses that have been performed on innovative LNG Offshore floating units to provide a qualitative and quantitative hazard assessment by predicting the consequences and the frequencies of these hazards, while improving the reliability of the installation and its availability. The paper will first introduce the LNG offshore industry outlining the different installations possibilities and the associated hazards. Then, based on recent projects, it will detail the risk-based methodology applied to ensure the safety and the profitability of such innovative installations when no rules are able to frame fully the development of these projects. Finally, after having pointed out the ins and outs of risk studies, a case study using most of the methods presented previously will be developed.
Full Scale CFD Validation on Thruster-Hull Interaction on a Semi-Submersible Crane Vessel in Transit Condition
Authors: Ottens Harald , Bulten Norbert , van Dijk Radboud
Published: November 2013

Heerema Marine Contractors operates three semi-submersible crane vessels; the Thialf, Balder and Hermod. The first two vessels are equipped with a DP system. The ability of each crane vessel to keep its position depends highly on the performance of the DP system of that crane vessel. The thrust efficiency of the DP system depends on the efficiency of the individual thruster, but also on the interaction of the thruster wake and the hull of the vessel.

Thruster-hull interaction is important during operations, but also during transits from one location to another. During the transits of the Balder and Thialf, the DP thrusters are used as propulsion. Understanding the thruster-hull interaction effects in this transit condition can result in an optimum thrust setting.

In previous validation studies CFD was used to assess the current loads and the thruster-hull interaction on a semi-submersible vessel. In these studies the CFD results were validated with a series of dedicated model tests. The comparison between the CFD and model test data shows that CFD is able to predict the relevant force components within a sufficient accuracy for engineering purposes.

However, Heerema Marine Contractors is mainly interested in full scale data. Unfortunately, not much full scale data is available to validate the extrapolation of model test and CFD results to full scale thruster efficiency. Therefore a first validation study is performed based on acquired full scale data during a transit of the Thialf in Q4 2011. Comparing the full scale test data with the CFD results shows that the CFD can be used to predict which settings is the most efficient.

Optimization of thruster settings on semi-submersible vessels is not trivial due to number and location of the azimuth thrusters. Using CFD simulations the power settings and azimuth angles of the thrusters were changed to obtain the optimal thrust setting during transit. In Q2 2012 the Thialf made her first transit after a dry-dock period in which the hull was cleaned and painted. Repeating similar tests conditions as in Q4 2011 demonstrates the effect of a clean hull. Additional tests demonstrated the effect of a more efficient thrust setting originated by the CFD results. The implications of the optimized azimuth setting in transit on the life time of the thruster is verified using CFD and FEM.

The paper addresses lessons learnt to improve the CFD simulations as well as practical aspects and limitations of thrust efficiency modeling using CFD. It demonstrates that CFD can be used to understand the associated flow physics and that CFD can be used to predict improvements in thrust efficiencies. In addition, some lessons learnt on full scale monitoring will be addressed.
Development on Aegir Reeling Pipeline Analyses by Test Validation
Authors: Karjadi Erwan , Boyd Helen , van Rooijen Reinout , Demmink Harm , Balder Thomas
Published: November 2013

Heerema Marine Contractors (HMC) is entering a new era of laying pipelines using the reel-lay method in order to be more cost effective for deep and shallow water pipeline installation projects. The new Deep water Construction Vessel (DCV) Aegir is designed to be able to reel/J-lay pipelines for a range of pipe dimension and water depth combinations. The paper describes how the full reeling cycles Finite Element Analysis (FEA) of the Aegir have been developed step by step from the development of the bend rig test, spooling-on to spooling-off FE models which is validated by the bend rig test program. The required material test program is performed to characterize the correct material behavior under plastic cyclic straining.

The know-how from the validation of the FEA of bend rig tests by performing the bend tests program is used to setup the full-reeling cycles simulation of spooling-on pipeline on the yard and spooling-off pipeline on board of the Aegir. A series of bend rig tests have been performed at Heriot-Watt University. Ovality measurements from the tests are compared with the predicted results from the bend rig FEA simulation model. Based on small scale specimen tests which are performed to describe the proper material behavior under plastic cyclic straining, a new material model has been proposed and discussed to provide a correct prediction of ovalization against the number of bend cycles. Comparison between the bend rig test measurements and the Aegir full reeling cycles simulation results is made by comparing the deformation of the pipe (ovalization) against a number of bend cycles. Discussion is given to justify the difference in the outcomes as well as the representation of the bend tests program for the qualification test program for reeling with the Aegir.
Validation of the Acceptability of 10x20 mm Specimens for Fracture Toughness Determination of High-Strength Steels
Authors: Walters Carey L. , Voormeeren Lars O. , Janssen Michael , Wallin Kim
Published: November 2013

Standards have traditionally required that fracture toughness specimens be the full thickness of the base material. However, this requirement may be unnecessary, especially if minimum specimen size dimensions based on plastic zone are met and the subsized specimens are statistically adjusted for the size effect. The current paper presents the results for full-thickness proportional Single Edge Notched Bending (SENB) specimens according to BS7448-1 that are 25 mm by 50 mm in cross-section and then compares these results to specimens of the same material that are 10 mm by 20 mm in cross section. The result is that for a temperature near the lower portion of the transition curve (−60°C to −70°C), the subsize specimens are in very good agreement. These results hold for two different loading rates. After correction for statistical size effect, the fracture toughnesses of the subsize specimens are within 10% of the full-size specimens. This is conservative. The difference is attributed to the statistical nature of fracture in the transition region.
An Ensemble Kalman Filter Data Assimilation Scheme for Modeling the Wave Climate in Persian Gulf
Authors: Serpoushan Nima , Zeinoddini Mostafa , Golestani Maziar
Published: November 2013

In recent years, application and evaluation of the efficiency of different data assimilation methods has been a subject of interest in both wave hindcasting and forecasting systems. The main goal of the current study is to assess the efficiency of an ensemble Kalman filter (EnKF) data assimilation scheme in improving the wave simulation results in Persian Gulf. The so called region plays an important role in the oil and gas industry due to its Geographical and Morphological location and housing a large number of offshore platforms.

A third generation wave model, SWAN, was employed in order to simulate the wave fields in the region. The three hours updated ECMWF wind data were used as the main driving force. The OpenDA toolbox, especially developed for efficient data assimilation purposes, was employed to smooth the chaotic nature of the non-linear wave simulation scheme. The OpenDA utilizes a number of methods that are based on Kalman filter algorithm but do not require the amount of computation efforts that are incurred by the classical filter algorithm. The EnKF is a variant of Kalman filter, where probability density function of a model state is represented by an ensemble of the model state.

Two sets of records for significant wave heights and peak wave periods were used in the analysis process with EnKF to estimate the error covariance matrix. At analysis time, the forecast error covariance was computed by using the model forecasts ensembles. In overall and for the wave climate modeling, the initial conditions of the numerical model were updated using the improved system state, up to the current computing time level. This is achieved by incorporating the previous measurements into the Kalman filter algorithm. The model was then run into the future, driven by the new improved state conditions.

The statistical results and diagrams showed that applying EnKF scheme leads to a noticeable improvement in significant wave heights. However, the accuracy of this technique was subjected to the location and number of observation stations and also ensemble size. With larger ensembles, results of error covariance estimation are more accurate but there is a limitation due to execution time of process and efficiency of the computations.
Flow Velocity and Impact Pressure in Liquid Sloshing
Authors: Song Youn Kyung , Chang Kuang-An , Ryu Yonguk , Kwon Sun Hong
Published: November 2013

Flow kinematics and impact pressure of a partially filled liquid sloshing flow produced by the periodic motion of a rectangular tank were studied experimentally. The main focus was on quantifying the flow velocities and impact pressures induced by the flow. The tank was filled with water at a 30% filling ratio and oscillated at a resonant frequency to generate the violent sloshing flow. The flow velocities were measured using the bubble image velocimetry technique. A total of 15 pressure sensors were mounted on the top wall and a side wall to measure the impact pressures. The local kinetic energy obtained by the measured local velocities was used to correlate with the corresponding pressures and determine the impact coefficient. It was observed that the impact coefficients differed by almost one order of magnitude between the side wall impact and the top wall impact, mainly due to the large difference between the local velocities.
Small Craft Assistant Information System Based on GPS and Google Earth in Real Time
Authors: Ryu Shinchiku , Shiotani Shigeaki
Published: November 2013

The system is aimed at establishing the information support system for small craft operators. This system can also be used for playback and simulation purpose. The combination of 3D map service of Google earth and GPS can supply real time position and 3D geographic virtual circumstance. In this study, authors make the small craft assistant information system based on Microsoft.Net technology, GPS and Google Earth.
Analysis of Pusher-Barge System With Different Maneuvering and Propulsion Devices
Authors: Yuba Douglas T. G. , Tannuri Eduardo A.
Published: November 2013

Pusher-barge system with different maneuvering and propulsion devices were modeled and analyzed. Both azimuth thrusters and conventional propulsion system (which is composed by rudder and propeller) were considered in the pusher. An additional azimuth thruster installed on the bow of the barges was also analyzed, in order to increase the maneuverability of the convoy.

Hydrodynamic derivatives for different pusher-barge configurations used in Tietê-Paraná river (B × L = 2 × 3, 1 × 2 and 1 × 1) were obtained from previously published works and complemented by captive model tests and CFD calculation executed in the context of the present project, presented in a complementary paper in this conference Grassi et al. (2013). Numerical models for each propulsion and maneuvering devices were obtained by standard formulations. A time-domain simulator was then implemented and the standard zig-zag and turning circle tests were simulated to compare performance of the different maneuvering and propulsion devices.

It was verified that pushers equipped with azimuth thrusters can increase the maneuverability of the system for slow speed navigation. For higher speeds, the conventional rudder and propeller pusher presents similar or even better maneuvering properties, since the effectiveness of the rudder increases.

The additional bow azimuth thruster can also improve maneuverability parameters, since the force applied at the bow increases the turning moment. However, its efficiency depends also on the speed and the instantaneous pivot-point of pusher-barge system. A broad discussion about the advantages and physical limitations of this additional bow azimuth thruster is presented.
Towing Tank Experiments on the Vortex-Induced Vibrations of a Long Flexible Cylinder in a Stepped Current
Authors: Huera-Huarte Francisco J. , Bangash Zafar A. , González Leo M.
Published: November 2013

We describe recent results showing the dynamic response, excited by vortex shedding, of a long flexible cylinder subject to a stepped current. The experiments were conducted at the Naval Architecture Department towing tank of the Technical University of Madrid (UPM) during March 2012. The tank is 100 m long with a cross-section of 3.8 × 2.5 m, and it is able to deliver speeds over 4 m/s. A supporting structure was designed in order to provide support for a 3 m long cylinder with an external diameter of 19 mm. The cylinder was instrumented with strain gauges providing curvature measurements in the in-line and the cross-flow directions at 11 locations along its length. Tension and drag forces were also measured at both ends of the model. More than 50 runs were conducted with the cylinder being placed vertically having its lower 65% length under the water free surface, connected to the structure by means of universal joints. The supporting structure allowed to configure different top end conditions and to apply different top tensions. Tests were conducted for Reynolds numbers as high as 34000. The cylinder had a low flexural stiffness and very low mass ratio m* of 0.67. Fundamental natural frequencies were in the range from about 4 to 7.9 Hz, and the cylinder responded in modes up to the third cross-flow. In this article we will describe the experiments and the instrumentation used, the modal tests conducted and the results obtained during the experiments.
Sensitivity Analysis of Buoyancy Modules Parameters of Lazy-Wave Flexible Riser
Authors: Sun Hua , Wang De-yu
Published: November 2013

This paper mainly studies the impact of the outer diameter, length and location of the buoyancy module of flexible riser on the overall performance of the riser and perform sensitivity analysis of these parameters. The model was built in ABAQUS to study on the section force and section moment in different cases by static analysis and dynamic analysis. The study shows that the outer diameter and location of the buoyancy module are both high-sensitivity parameters. The outer diameter mainly has a great impact on section moment of the riser and the location has an impact both on section force and section moment. However, the impact of length for the overall performance of the riser is weak. Sensitivity Analysis of buoyancy modules parameters in this paper plays a certain reference to the design of the buoyancy modules of the lazy-wave riser.
Development of an Autonomous Human Monitoring System for Preventative Safety in Sea Transportation
Authors: Arima Masakazu , Kii Shotaro
Published: November 2013

The purpose of this study is to develop a human monitoring system for preventative safety in sea transportation. The final goal of this research is to be able to detect even a small change in the physical condition of the crew such as inattention or lapse of concentration during a voyage and to call his/her attention to the navigation of the ship before accidents or dangerous minor incidents occur. This paper deals with autonomous facial expression monitoring system and ECG analysis using a mini physiological measuring system. Ship’s captain and/or chief officer is usually walking around in the navigation bridge so as to maintain ship’s safety. Human monitoring in sea transportation is more difficult than cases of aeroplane pilot, train or bus driver who are sitting on their own seat during operation. The authors have established an autonomous facial-expression monitoring system, named ‘KII (Kinetic Information Integrator) system.’ This system consists of multiple network cameras and Microsoft’s KINECT sensor. The KINECT sensor has an ability to detect subject’s posture and skeleton position in three dimensions. At the least two network cameras will be controlled autonomously so as to follow subject’s face from different directions even though he or she is walking around in the navigation bridge. And the rest network cameras are following his activities by zoomed out. Field experiment of the KII system has been conducted on board the training ship ‘Fukae-maru’ of Kobe University. Navigation officer’s face was followed by the system during operation, and the effectiveness and validity of the system has been demonstrated. It is thus thought to reach the stage of practical application. The heart is controlled by the autonomic nervous system, and the sympathetic nervous system and parasympathetic nervous system are well known to represent the mentally stressed or relaxed states, respectively. Heart rate variability was analysed and subject’s physiological and psychological changes during navigation were also discussed.
Design Parameter Estimation of Wave Height and Wind Speed With Bivariate Copulas
Authors: Tao Shanshan , Dong Sheng , Xu Yinghui
Published: November 2013

The data of annual extreme wave height and corresponding wind speed at a platform in Bohai Bay is hindcasted by a numerical model from 1970 to 1993. Common-used design probability distributions, such as Gumbel distribution, Weibull distribution, and lognormal distribution are applied to fit the data of extreme wave height and concomitant wind speed, respectively. Then the best-fitted marginal distributions of annual extreme wave height and wind speed can be selected. Bivariate normal copula and Frank copula are utilized to construct joint distribution of these two random variables. Based on empirical base shear equation of the on-site fixed jacket platform, the maximum base shear can be calculated under the same joint return period of the wave height and wind speed. The results show that the proposed joint probability models constructed by bivariate copulas result in lower the design environmental parameters because of the consideration of correlation between random variables. Eventually the investment cost of marginal oil fields could be relatively reduced.