bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of Sunk Cost in Engineering Idea Generation: An Experimental Investigation
Authors: Viswanathan Vimal K. , Linsey Julie S.
Published: August 2013

Researchers and design practitioners advocate building physical models of ideas at early stages of the design process. Still, the cognitive effects of physical models remain largely unknown. Some studies show that physical models possess the potential to facilitate the generation of high quality ideas. Conversely, other studies demonstrate that physical models can lead to design fixation. A prior controlled study by the authors failed to detect fixation due to early stage physical models. Based upon these conflicting results, this study hypothesizes that the fixation observed in prior studies can be explained by the Sunk Cost Effect. The Sunk Cost Effect pertains to an individual's reluctance to choose a different path of action once he/she invests a significant cost (money, time, or effort). According to this theory, as designers spend more time, money or effort in building physical models, they tend to generate ideas with lower novelty and variety. The prior observational studies use complicated design problems with higher costs compared to the controlled study, possibly explaining the difference in results. This study also hypothesizes that physical models supplement designers' erroneous mental models. The authors investigate these hypotheses through a controlled, between-subject experiment with five conditions: Sketching Only, Metal Building (low time cost), Plastic Building (high time cost), Metal Constrained Sketching, and Plastic Constrained Sketching. In each condition, subjects construct their ideas using materials specified by the name of the condition. The constrained sketching conditions assist in determining if participants tend to limit their ideas to only ones that can be built with given materials even though they are instructed to write down all ideas. The results confirm that the sunk cost of building plays a vital role in the observed fixation; thus, physical models do not inherently cause fixation. Moreover, results also show that physical models supplement designers' erroneous mental models, leading to higher quality ideas. To minimize sunk costs very early in the design process, models should be built with materials requiring minimal time, cost, and effort for the designers.
Facilitating Higher-Order Learning Through Computer Games
Authors: Siddique Zahed , Ling Chen , Roberson Piyamas , Xu Yunjun , Geng Xiaojun
Published: August 2013

Engineering education needs to focus on equipping students with foundational math, science, and engineering skills, with development of critical and higher-order thinking so they can address novel and complex problems and challenges. Learning through a medium that combines course materials with game characteristics can be a powerful tool for engineering education. Games need to be designed for higher order engagement with students, which go beyond remembering, understanding and applying of engineering concepts. In this paper, we present design, development, implementation, and evaluation of a game for engineers. The developed game is founded on experiential learning theory and uses enhanced game characteristics. The racecar game has been designed to facilitate higher-order learning of geometric tolerancing concepts. The course module has been developed and implemented, with assessment of outcomes. The results show that students using the game module, when compared with the control group (lecture-based instruction), had significant improvements when addressing questions that involved higher-order cognition. Survey results also indicate positive student attitudes towards the learning experience with game modules.
Wave Effects on Vortex-Induced Motion (VIM) of a Large-Volume Semi-Submersible Platform
Authors: Gonçalves Rodolfo T. , Rosetti Guilherme F. , Fujarra André L. C. , Nishimoto Kazuo , Oliveira Allan C.
Published: August 2013

Aiming to complete the results presented before by Gonçalves et al. (2011) – Experimental Study on Vortex-Induced Motions (VIM) of a Large-Volume Semi-Submersible Platform, OMAE2011, the present work brings new experimental results on VIM of a large-volume semi-submersible platform, particularly concerning its coexistence with waves in the free surface. The VIM tests were performed in the presence of three regular waves and also three different conditions of sea state. According to the results, considerable differences between the presence of regular or irregular waves were observed. The motion amplitudes in the transverse direction decreased harshly when the regular waves were performed and no VIM was observed. In the case of sea state condition tests, the amplitudes decreased slightly but a periodic motion characterized by the VIM was observed. The results herein presented concern transverse and yaw motion amplitudes, as well as spectral analyses.
Stability of Submarine Foundation Pits Under Wave Loads
Authors: Bubel Julian , Grabe Jürgen
Published: August 2013

Shallow foundation structures offer ecological benefits compared to pile foundations as less noise is emitted at sea floor level during construction process. On the other hand, shallow offshore foundations can rarely be placed on top of the sea floor. Weak soils usually need to be excavated to place the foundation structure on more stable ground and thus, anthropogenic submarine pits result. Steep but stable slopes of the pit meet both economic and ecologic aims as they minimise material movement and sediment disturbance. According to Terzaghi [1] the angle β between slope and the horizontal of the ground surface of cohesionless soil is at most equal to the critical state friction angle φc. However, it can be observed that natural submarine slopes of sandy soils are always much more shallow. Artificial (temporary) slopes do not appear and behave as natural submarine slopes, since the latter are already shaped by perpetual loads of waves, tide and mass movements. Physical simulations of different scales were presented at the OMAE 2011 [2] to analyse the stability of artificial submarine slopes of sandy soil in the North Sea. The laboratory tests focused on gravitational forces and impacts from the excavation processes. This paper presents additional numerical simulations of wave-induced bottom pressure on the suggested submarine foundation pits. Furthermore, in-situ tests will be performed in 2012 and 2013. Both dredging process and resulted foundation pits will be considerably surveyed.
Prediction of Triaxial Compressive Strength of Geomaterials Based on a Failure Criterion
Authors: Bineshian Hossein , Bineshian Zahra
Published: August 2013

Ramamurthy et al strength criterion is applicable only for compression. Tensile strength and unconfined compressive strength cannot be calculated by the criterion. Ramamurthy et al criterion contains two parameters as inherent constants of geomaterials that are known as B and α. A popular method to predict the strength by a certain criterion is using the proposed values for the criterion’s parameters, authors in this paper suggested suitable practical values for the parameters and a precise equation for B for a wide range of geomaterials. Also especial consideration has been pertained for soft geomaterials to calculate the parameters for different conditions of weak planes and loading direction. Moreover authors have presented linear conversion and nonlinear regression model for Ramamurthy et al criterion to extract the mathematical coefficients and the strength criterion’s parameters. Using these parameters for seabed geomaterials will present a fast, useful and credible prediction for the compressive strength by this modified strength criterion.
Experimental Studies of a Floating Cylindrical OWC WEC
Authors: Sheng Wanan , Flannery Brian , Lewis Anthony , Alcorn Raymond
Published: August 2013

Oscillating water column (OWC) wave energy converters (WECs) are a popular type of wave energy devices, due to their advantages over many other WECs. For example, OWC WECs normally have no moving components in sea water, and have a small torque and a high rotational speed for a certain power take-off. Practically, some foundation-type pioneer plants of OWC WECs have been very successful in generating electricity to grids continuously. In order to obtain higher yields of wave energy production, it is proposed to move the OWC WECs to open and deep water regions, and for the purposes of economics and reliability, the OWC WECs are designed to be floating devices, with a potential of utilizing the device motions to improve wave energy conversion capacity. To further understand the OWC WEC performances in waves, a floating cylindrical OWC has been designed and tested in an ocean wave tank. In the model test, five different size orifices are designed to represent different damping levels of the air flow. In the experimental study, a systematic series of tests in both regular and irregular waves has been conducted to help understand the hydrodynamics and aerodynamics of the generic OWC device.

In the model test, the interior water surface motion and the pressure in the air chamber are measured and based on them the primary power take-off by the device can be calculated. Alternatively, the power take-off can be calculated by the pressure measurement only or by the interior water surface measurement only due to the unique relation of the pressure drop and the airflow passing through the orifices. In addition, in the experiment, the motions of the floating structure have also been measured, from which it is possible to correlate the motions and the wave energy extraction.

As expected, the orifices exhibit a quadratic non-linear relation between pressure and the flowrate. Though simple, the orifice power take-off system may exhibit a similar flow feature to that of an impulse turbine, thus an appropriate model to the impulse turbine.
Experimental Research on Fatigue Behavior of Adhesively Bonded Steel Single-Lap Joints
Authors: Jiang Xiaoli , Kaminski Miroslaw (Mirek) Lech
Published: August 2013

The introduction of aluminum, Fiber-Reinforced Plastics (FRP), and other new materials to the shipbuilding industry has meant that joining materials with adhesive bonds has become a promising alternative to welding. However, unlike the aerospace and automotive industries, the application of adhesive bonds in ship structures remains sporadic because of limited practical knowledge, relatively high amplitude cyclic loads, and a severely corrosive marine environment. In order to investigate the potential of adhesive bonding for marine structures, representative structural details have been selected and tested. The present paper discusses the results of a series of fatigue tests on steel single-lap adhesively bonded joints, including the effects of loading frequency, stress level, and random fatigue loading. These results will be used to construct a guide for the design of adhesive bonding in marine structures.
An Exploratory Study on the Working Principles of Energy Saving Devices (ESDs): PIV, CFD Investigations and ESD Design Guidelines
Authors: Dang Jie , Dong Guoxiang , Chen Hao
Published: August 2013

The Maritime Research Institute Netherlands (MARIN) has recently started a Joint Industry Project (JIP) called ESD-JILI, investigating the working principles of energy saving devices (ESDs). Within the framework of this JIP, three ESDs have been selected and thoroughly investigated. They are a Pre-Duct with an inner Stator (PDS), a Pre-Swirl Stator (PSS) with asymmetric blade design and Hub Fins (HFs). The investigations have been carried out by using dedicated force and moment sensors to measure all the components of the ESDs independently during the propulsion tests, by using Particle Image Velocimetry (PIV) to measure the flow before, in-plane and behind the propeller and the ESDs, and by using Smart Ship Model technology (Wijngaarden 2011) to simulate the full-scale wake field during the model tests to gain insights on scale effects of the ESDs. At the same time, computational fluid dynamics (CFD) calculations are also carried out in order to further deepen the understanding of the working principles of the selected ESDs, and to assist the ESDs designs under certain guidelines. Some of the results of the study have been published to the Greenship’2011 Conference (Dang et al 2011). The flow details around the propulsion system with the PDS, which were obtained by both PIV measurements and CFD calculations, and the energy balance of the ship-propulsion system with a PDS are further investigated and reported here. Based on the results of the studies, the principle guidelines for ESD designs for single screw merchant ships have been proposed.
Asymmetric FPSO Roll Response due to the Influence of Lines Arrangement
Authors: Ferreira Marcos Donato , de Oliveira Mauro Costa , Carvalho Rafaella Cristina , Sphaier Sergio Hamilton
Published: August 2013

In the development of the mooring design of FPSOs in spread mooring system (SMS) configuration, it was observed that the utilization of asymmetric riser arrangement in deep waters might lead to an asymmetrical roll response of the FPSO. In particular, concentrating all riser connections on the portside, it could be observed that roll and heave coupling under the influence of the riser dynamics might lead to a much lower roll response associated with waves coming from portside than from the starboard direction. Simulations were carried using an in-house time domain simulator, where the ship hydrodynamic behavior was represented through the use of impulse response functions and the lines dynamic through the use of non-linear finite element method, using an explicit integration scheme and a lumped mass approach. Non-linear viscous effects could be easily associated to the ship and line velocities. Measured motion responses of an actual FPSO in operation in Campos Basin are compared with the computations.
Potential Galloping Motions of Piggyback Pipeline Geometries in Strong Currents
Authors: Elegbede Adeshina , Gudmestad Ove T.
Published: August 2013

Piggyback configurations of pipelines, such as a Direct Electrical Heating (DEH) cable mounted on production flowlines, are becoming a common occurrence in the offshore oil and gas industry and they have been observed to excite into a type of flow-induced vibration called galloping in the presence of strong currents at free span locations.

This work was aimed at studying potential flow induced galloping vibrations of piggyback type of pipelines commonly used on offshore installations in the oil and gas industry. Tests were carried out in a 12m long, 0.7m wide and 1.2m deep current flume tank located at the NTNU/SINTEF Hydrodynamic Laboratory in Trondheim, Norway. The tank has a test rig with cylinders suspended horizontally on a set of springs mounted on it. Reduced velocities were ranging from 4 to 15, depending on the equivalent diameter of the piggyback pair.

In this experimental work, the effects of different diameter ratios and the angle of attack of the flow on the cylinders arranged normal to the flow were investigated. Three different diameter ratio cases were investigated: D+0.5D, D+0.32D and D+0.25D. Attack angles 0°, 30°, 60°, 90°, 120°, 150° and 180° were tested for these 3 diameter ratios giving a total of 21 test cases.

The results obtained show that, for all cases of diameters ratios, high response amplitude ratios, as high as 1.7, can occur at reduced velocities less than 10 when the angle of attack is at 90°. It was also observed that vibrations that are characteristic of galloping instabilities occurred at an attack angle of 180° for the D+0.5D and the D+0.32D configurations. For the D+0.25D case, the response amplitudes were similar to a VIV situation. Comparing the response of the different diameter ratios show that the largest pipeline to piggyback ratio gives the largest responses for all attack angles.
Optimized Global Sizing Approach for Gulf of Mexico Production Semisubmersible
Authors: Williams Neil
Published: August 2013

A deep draft production semisubmersible together with steel catenary risers (SCRs) provides a cost-effective wet-tree solution for the deepwater Gulf of Mexico. The major challenge in determining an appropriate hull configuration for the semisubmersible is ensuring acceptable performance of the SCR system, both in terms of strength and fatigue. This paper presents a hull and mooring configuration sizing methodology for a production semisubmersible that results in the system being an optimized riser support platform. The methodology is illustrated through an example Gulf of Mexico deepwater application.
Qualification of Unbonded Dynamic Riser With Carbon Fiber Composite Armours
Authors: Lambert Anaïs , Do Anh-Tuan , Felix-Henry Antoine , Grosjean François
Published: August 2013

The development of Ultra Deep Water (UDW) oil and gas fields, down to 3000 m and beyond, requires high specification flowline and riser systems. At these depths, the flexible pipes must withstand high axial loads and severe dynamic loadings generated by currents, waves and vessel motions. Moreover, the constraints generated by the dynamic loadings are often combined to corrosion issues linked to the presence of CO2 and H2S. In case of sour service application, the structural layers of a classical flexible pipe require the use of steel with reduced mechanical properties compared to a sweet service application. The combination of UDW and sour service applications consequently lead to a riser design of considerable top tension.

The main challenges of such applications are the suspended weight and the fatigue / corrosion performances.

Carbon fiber composite have demonstrated high specific strength and outstanding corrosion and fatigue damage resistance. The use of carbon fiber composite instead of conventional steel for the tensile armour layers of flexible pipes represents a great alternative for the development of UDW applications combined with sour service conditions.

Technip has been engaged for a number of years in the development and qualification program of Carbon Fiber Composite (CFC) Armour. In 2011, an important step has been passed with the successful realization of a full-scale tension-flexion dynamic test.

The program of the full-scale dynamic test is based on a representative Brazilian offshore project, a typical UDW application. The CFC prototype structure was designed considering a 9” gas export riser installed at a water depth of 2140m, in free hanging configuration. The riser is made of 2 parts: a top riser with CFC armours and a bottom riser with steel armours.

1.8 millions of cycles were performed without damage, combining internal pressure, tensile loading and bending cycling. The whole test was monitored by acoustic emission to detect the potential damage of the CFC armours.

After explaining the advantages of CFC structures compared to traditional steel structures, the paper will focus on the realization of the full-scale dynamic test program. It will detail the design and manufacture of the prototype structure, the construction of the test program representative of the offshore conditions first and then extended to more severe loadings. The paper will also present fatigue analysis and the construction of the CFC fatigue curves.
Optimization of Short-Crested Deterministic Wave Sequences via a Phase-Amplitude Iteration Scheme
Authors: Schmittner Christian , Hennig Janou
Published: August 2013

For the deterministic investigation of rare phenomena like capsizing, broaching or wave impacts, methods for the generation of deterministic wave sequences are required. These wave sequences can be derived from full scale measurements, numerical simulations or other sources. Most methods for the generation of deterministic wave sequences rely as a backbone on linear wave theory for the upstream transformation of the wave train from the target position in the wave basin to the position of the wave maker. This implies that nonlinear wave effects are not covered to a full extend or completely neglected.

This paper presents the extension of a method for the generation of deterministic waves presented during OMAE 2009. The method improves the quality of the generated wave train via an experimental optimization. Based on a first wave sequence generated with linear wave theory and measured in the wave basin, the phases and amplitudes of the wave maker control signal are modified in frequency domain. The iteration scheme corrects for both shifts in time and in location resulting in an improved deterministic wave train at the target location. The method is extended to short-crested seas. The paper includes results of this method applied to a 3D wave basin.
Model Tests on a Radial Wellbay Spar in Gulf of Mexico, Norwegian Sea and Offshore Brazil Environments
Authors: Murray John , Muehlner Edmund , Banumurthy Surya , Choi Guibog
Published: August 2013

A model test campaign on a 1:50 scale model of a Radial Wellbay Spar (RAW) Spar was carried out at the OTRC facility in College Station, Texas. The campaign subjected the model to wind, wave, and current environments from the Central Gulf of Mexico, the Norwegian Sea, and offshore Brazil. Time traces of dynamic wind loads were predetermined from computations using drag coefficients and estimated wind load areas of the topsides. A servo controlled line mechanism was used to apply the wind load to the model topsides. Current forces were modeled using static weights connected at the appropriate elevation on the model. Ten (10) top-tensioned risers (TTRs) were modeled in terms of stiffness and top tension using four equivalent model TTRs. Horizontal restoring forces of the prototype mooring were modeled using a four-model line arrangement. The model was instrumented to measure six-degree-of-freedom rigid body motions, air gap around the deck, wave run-up, water elevation in the riser gap in the hard tank, and mooring and TTR tensions. Global loads on an internal structural component between the centerwell device and hard tank were measured in all environments. Data comparisons were based on selected time traces of various responses and Weibull distributions to predict extreme values. In general, good agreement was found between the measured and predicted values.
Benefits of Ultrasonic Peening Treatment in Fatigue Improvement of Welded Elements
Authors: Kleiman Jacob , Kudryavtsev Yuri , Lugovskoy Alexander
Published: August 2013

The Ultrasonic Peening (UP) is one of new and promising processes for fatigue life improvement of welded elements and structures. During the different stages of its development the UP process was also known as ultrasonic treatment (UT), ultrasonic impact treatment (UIT), ultrasonic impact peening (UIP). The beneficial effect of UP is achieved mainly by relieving of harmful tensile residual stresses and introducing of compressive residual stresses into surface layers of material, decreasing of stress concentration in weld toe zones and enhancement of mechanical properties of the surface layers of the material.

The results of fatigue testing of welded elements made of regular and high strength steels in as-welded condition and after application of UP will be presented. The yield strength of considered materials varied from 250–350 MPa to 700–1000 MPa. It is shown that UP is the most effective and economic technique for increasing of fatigue strength of welded elements in materials of different strength. These results also show a strong tendency of increased fatigue strength of welded elements after application of UP with the increase in mechanical properties of the material used. It allows using to a greater degree the advantages of the HSS in welded elements, subjected to fatigue loading.
Dynamic Selection of Ship Responses for Estimation of On-Site Directional Wave Spectra
Authors: Vincent Andersen Ingrid Marie , Storhaug Gaute
Published: August 2013

Knowledge of the wave environment in which a ship is operating is crucial for most on-board decision support systems. Previous research has shown that the directional wave spectrum can be estimated by the use of measured global ship responses and a set of transfer functions determined for the specific ship. The approach can either be based on parametric or Bayesian (non-parametric) modelling, and in both cases a set of three ship responses usually provides the best estimation. The optimal response combination of three responses at any time depends on the environmental conditions and the operation of the ship. Since measurements of more than three responses are usually available, a quick, dynamic selection procedure of the three signals best suited for the wave spectrum estimation procedure is essential.

In the present paper the concept of a selection method based on a simple pre-estimate of the wave spectrum is suggested. The selection method needs to be robust for what reason a parameterised uni-directional, two-parameter wave spectrum is treated. The parameters included are the zero up-crossing period, the significant wave height and the main wave direction relative to the ship’s heading. The procedure basically seeks to minimise the difference between a set of spectral moments derived from a measured response spectrum and the corresponding response spectrum calculated from the parameterised wave spectrum and the transfer function for any given response. Subsequently, the three responses with the best overall agreement are selected for the actual estimation of the directional wave spectrum.

The transfer functions for the ship responses can be determined using different computational methods such as striptheory, 3D panel codes, closed form expressions or model tests. The uncertainty associated with transfer functions depends on the computational method used, relative heading, frequency and type of response. This uncertainty is conceptually taken into account in the selection procedure using the First Order Reliability Method (FORM).

However, specific assessment of the uncertainties has not been carried out, but is subject to later studies.
Vortex-Induced Vibration of Two Side-by-Side Circular Cylinders of Different Diameters in Close Proximity in Steady Flow
Authors: Rahmanian Mehran , Cheng Liang , Zhao Ming , Zhou Tongming
Published: August 2013

Vortex-induced vibrations of two side-by-side cylinders of different diameters in steady incompressible flow are studied. The diameter ratio of cylinders is fixed at 0.1. The Reynolds number is fixed at 5000 based on the large cylinder diameter and free stream velocity. A Petrov-Galerkin finite element method is used to solve the two dimensional Reynolds-averaged Navier Stokes equations using the Arbitrary Lagrangian Eulerian scheme with a SST k-ω turbulence model closure. The numerical method has been validated against available experimental results. Then, the effects of natural frequencies of the cylinders on the vibration amplitude and vortex shedding regimes are investigated. It is found that for the range of considered parameters, collision of the cylinders is dependent on the difference of the natural frequencies of the cylinders.
Hyperbaric Rock Cutting
Authors: Miedema Sape A. , Zijsling Djurre
Published: August 2013

Under atmospheric conditions rock cutting is mostly brittle; either based on tensile cracks or based on shear cracks, although ductile cutting is possible. It is known from the drilling industry that under very high hydrostatic pressures often a sort of ductile cutting process occurs. Cutting under very high hydrostatic pressures is called hyperbaric cutting. Combining the cutting theory of water saturated sand of Miedema and the classic rock cutting theory of Merchant, the 2M theory, results in a new application of the theory for hyperbaric rock cutting. The new theory contains the pore pressure and the cohesive terms. To verify this theory the measurements of Zijsling (1987) are used, which go up to pressures of 1000 bar. A complication is that the chips cut will start to curl, but the contact length of the chip cut with the blade is unknown. Using the equilibrium of moment’s, results in a method for determining this contact length. In the specific case a contact length of about 4–5 times the layer thickness is found, resulting in an almost perfect match with the measurements. The paper shows the measurements and the theory.
Comparison of Recent Parametric Trenched and Partially Embedded/ Spanning Pipelines With DNV-RP-F109 Load Reduction Design Curves
Authors: Griffiths Terry , Shen Wenwen , Xu Mengmeng , Leggoe Jeremy
Published: August 2013

An extensive series of 2D CFD analyses of subsea pipelines with parametrically varying seabed profiles have been performed in the past two years. These cases feature variations on wave and current flow conditions with pipeline partial embedment or spanning which extend beyond the range of conditions which have been published to date. This paper presents a comparison of the reduction factors calculated from this work with DNV-RP-F109 load factors and previous published research.

At present, the DNV-RP-F109 partial embedment / trenched pipeline load reduction factors are applied in both absolute stability analysis and also as a reduction factor on hydrodynamic force-time histories used in dynamic stability analysis. The suitability of this load factor reduction for dynamic stability analysis will also be considered.

In addition, a limited number of cases have been constructed in 3D which provide some initial insights into the variation of hydrodynamic loads across a pipeline span as a function of finite span length, enabling the validity of applying the 2D DNV load reduction factors across a 3D span to be considered. The 3D cases also consider inclined attack angles, and the effect they have on hydrodynamic forces across a span.
Dynamic Responses of the Floating Cage System in Current and Waves
Authors: Li Li , Fu Shixiao , Li Runpei
Published: August 2013

In this paper, based on the Morison equation and FEM, we studied the dynamic responses of the floating cage system in currents and waves. The nets are modeled by truss elements, the current and wave forces are calculated based on the Morison equation at each time step. The floater is modeled by beam elements, and the hydrodynamic forces from wave and current are also calculated by Morison equations. The sinker is modeled by adding a circular mass bar on the bottom of the whole structure. The effects of the flexibility on the dynamic responses of the floater are investigated by studying the structural deformations of the floater. The dynamic response of the system in different current and wave conditions are studied as well.
Formal Safety Assessment of Cargo Ships at Coasts and Open Seas of Turkey
Authors: Akyildiz Hakan , Mentes Ayhan , Helvacioglu Ismail Hakki
Published: August 2013

This paper presents an evaluation of Formal Safety Assessment framework for cargo ships at coasts and open seas of Turkey. Based on Turkish Under secretariat of Maritime Affairs casualty reports, this study identifies risk factors that have significant, independent effects upon the likelihood of ship and offshore operations. A case study is carried out to determine the most common causes of unintentional damages on cargo ships using FSA. It is obvious that shortage of skilled crew and crew training become very important for safety. This would require a compulsory course related to the human functions such as knowledge of regulations and use of equipment. Finally, some conclusions and suggestions are drawn concerning the needs to reduce the risks and to improve certain safety measures at coasts and open seas of Turkey.
Elastic Floating Unit With Piezoelectric Device for Harvesting Ocean Wave Energy
Authors: Mutsuda Hidemi , Watanabe Ryuta , Hirata Masato , Doi Yasuaki , Tanaka Yoshikazu
Published: August 2013

The purpose of this study is to improve FPED (Flexible PiEzoelectric Device) we have developed. The FPED consisting of piezo-electric polymer film (PVDF) is a way of harvesting electrical energy from ocean power, e.g. tide, current, wave, breaking wave and vortex. We also propose an Elastic Floating unit with HAanging Structures (EFHAS) using FPED. The EFHAS consists of floating unit and hanging unit. In this study, we investigated electric performance of FPED and EFHAS and also modified internal structure of FPED to increase electrical efficiency. As a result, Electric performance is increasing with increasing number of PVDFs laminated in FPED. Multilayer type of FPED can rapidly increase electric efficiency. Electric power can be improved by FPED attached a bluff body with relative density. Electric performance of floating type for floating unit of EFHAS is better than that of submerged type. Distance L/λ = 0.4 between floaters of floating unit is suitable for highly electric performance. In hanging unit of EFHAS, it is possible to increase electric power per unit area with increasing number of stairs. In conclusion, we showed the EFHAS with the FPED could be useful for harvesting ocean wave energy.
A Comparison of Direct Calculation Approaches Applied on the Fatigue Strength Assessment of a Panamax Container Ship
Authors: Li Zhiyuan , Mao Wengang , Ringsberg Jonas W.
Published: August 2013

Today, it is common practice to carry out fatigue assessments of ship structures using direct calculation procedures. A direct calculation analysis of a ship’s fatigue strength involves hydrodynamic analysis, stress response evaluation followed by fatigue damage calculation. Many numerical codes are available for these types of analyses. They could yield different values in a fatigue life prediction because of the different degrees of complexity in the computation of the ship’s response. For example, hydrodynamic loads can be calculated using the strip theory or the panel method. The stress response to these loads can be computed using a beam theory or more advanced analyses, such as global and/or local finite element analyses. In a direct fatigue analysis for ship design, spectral methods have been dominating but there is a growing interest in time-domain fatigue damage calculation procedures. The objective of the current investigation is to compare four commonly used direct calculation methods against measurement data. The comparison is carried out by making a case study on a Panamax container ship on which full-scale measurements have been performed. The computational efforts involved in the application of the current direct calculation methods are compared and their applicability in ship fatigue design is discussed.
Measurement of Bending Residual Stress on a Hull Section of a Submarine
Authors: Ficquet Xavier , Bowman Ashley , Goudar Devkumar , Körner Manuel , Kingston Ed J.
Published: August 2013

Explicit understanding of the residual stress field of primary submarine pressure hull induced during fabrication will improve the fidelity of numerical analysis and experimentation. Hence, supporting operational envelope and design life extension initiatives.

The fatigue lifetime of a submarine hull depends on the loads generated by hull contraction under the effect of hydrostatic pressure and the residual stresses existing in the absence of external loading. The use of numerical simulation allows a straightforward calculation of the stresses induced by the hydrostatic pressure. The effect of residual stress could be determined using the current failure assessment procedures, like BS7910 and R6. However it is more intricate to determine the residual stresses resulting from the sheet bending process combined with the sheet assembly using a multipass welding process.

There are several measurement techniques available to measure residual stresses. They are often classified by their level of destructiveness and their penetration.In order to compare the different measurement techniques an elastic-plastic bent beam sample has been chosen as it is very comparable to the residual stress field induced during the sheet bending process used in the submarine structure. Four bent beams have been measured using five different techniques: Incremental centre hole drilling, ring core, neutron diffraction, slitting and deep hole drilling technique. The results from measurement techniques show an excellent agreement when compared with the FEA.

In order to measure a full scale Rubis class submarine hull a limited number of techniques can be used, as the technique needs to be portable. The Deep Hole Drilling (DHD) technique was chosen because the neutron diffraction would require extracting a small test sample of about 400mm × 400mm, hence redistributing the residual stresses that were intended to be measured. Six measurements were carried out at different angular positions to detect variability in manufacture on a Rubis class submarine and a probabilistic calculation was done using all six DHD measurements. The Rubis class measurement results are also compared with two other submarine types, found in the literature.

Understanding the three-dimensional behaviour of residual stress in this type of structure provides a valuable resource to the numerical modelling community. The results can also support fatigue and fracture experimental work and may help increasing the operating life of 28 year old French nuclear submarine.
Irregular Wave Simulation and Fatigue Damage Evaluation of a Flexible Riser Subjected to Bi-Modal Sea States
Authors: Tan Zhimin , Hou Yucheng , Zhang John , Sheldrake Terry
Published: August 2013

This paper presents the fatigue evaluation of a flexible riser subjected to bi-modal sea states, where the local wind and swell conditions act simultaneously, and is observed in many offshore regions including Brazil and West Africa. Due to the irregularity of the riser responses, the traditional, regular wave approach for assessing the fatigue damage of a flexible pipe cannot be applied without significant simplifications. A typical deviation would be to treat the combined swell and wind conditions at sea as two sets of separate cases. The regular wave approach can then be applied and the summation of the damage of both cases defined as the final damage of the pipe.

As an alternative, this paper presents a more theoretically accurate irregular wave approach. The entire irregular wave simulation was first performed using the commercial software, OrcaFlex™, together with a tensile wire stress model developed in-house. The model implements the pipe bending hysteresis behavior during dynamic excitation, producing corresponding time history stress results, which are used to assess the fatigue damage using a rain-flow counting method. Two case studies are presented, the first being a dynamic simulation performed with two wave trains generated based respectively on the given swell and wind sea spectrums. In the second case study, a single wave train is generated based on the combined spectrum of the swell and wind sea states. Both results are compared with those obtained by the traditional regular wave approach and a preferred analysis method is recommended based on the conservatism and time efficiency.
Current Loads on Net Panels With Rhombic Meshes
Authors: Enerhaug Birger , Føre Martin , Endresen Per Christian , Madsen Nina , Hansen Kurt
Published: August 2013

In this paper, hydrodynamic load models applicable to rhombic net structures are discussed and compared to experimental results with net panels in steady currents. Net panels with mesh sizes and mesh opening angles as is commonly used in fishing gear, were tested in the SINTEF operated flume tank in Hirtshals, Denmark. Drag and lift forces acting on the net panels were measured in two different water currents with attack angles ranging from 0 to 90 degrees.

These measurement data were used as a benchmark to compare the performance of several established mathematical models of hydrodynamic loads on panels. Subsequently, an element-based approach with summation of lift and drag forces acting on all the individual twines of the element was performed, and the output from the simulations was compared with experimental data. The correspondence between results from the numerical simulations and experiments were in general quite acceptable for higher angles of attack, while the lack of a wake model overestimated the drag at lower angles. Lift was predicted with high accuracy for all panels.
Best Practice Guidance for Evaluating Knock-Down Factors in Corrosive Environments
Authors: Holtam Colum M. , Schneider Charles R. A. , Slater Graham
Published: August 2013

The term knock-down factor is commonly used to describe the reduction in fatigue life in a corrosive environment (e.g. sour service) compared to performance in air. However, the mere concept of such a reduction factor is potentially misleading, particularly when comparing different welding procedures that demonstrate different in-air performance. This paper examines the concept and calculation of so-called knockdown factors.

To demonstrate the performance of girth welds in a corrosive environment, strip fatigue tests are conducted in air and in a simulated service environment, to determine an appropriate knock-down factor, which is then applied to the base design curve. However, there are a number of ways that such knock-down factors can be calculated, with different degrees of conservatism. For example, two different welding procedures may exhibit a different fatigue performance in air, but a similar performance when tested in a sour environment. The better performing weld (in air) is therefore assigned a greater knock-down factor, and possibly a more stringent sour design curve. In other instances, fatigue performance in air may significantly exceed that required. The determined knock-down factor, between strip tests in air and in a sour environment, can then be very large. Applying this reduction factor to the design curve results in a very stringent sour design curve, and may penalize the use of a girth welding procedure that results in good in-air fatigue performance.

There are no explicit, published guidelines for calculating corrosion fatigue knock-down factors. This paper describes an approach, based on experience and considering best practice guidance for the statistical analysis of fatigue data obtained from welded joints. The method is demonstrated using published sour corrosion fatigue endurance data, evaluating both mean and design curves.
Large Diameter, Deep Water PLEM Concepts
Authors: Damsleth Per , Abdalla Basel , Tang K. C.
Published: August 2013

The export of gas from deepwater production systems can involve a large diameter pipeline with a manifold (PLEM) at the deep end. The PLEM commingles the flow from multiple smaller diameter risers, or flowlines, isolates the pipeline and provides a subsea pig launching and receiving facility. Connecting the PLEM to a large diameter (36” to 46”) gas export line is a major challenge because of the very stiff pipe. Horizontal diverless connection systems can align the pipeline terminations using powerful hydraulic jacks but the size and weight of the spools and equipment for such large diameter tie-ins make them difficult to handle. Therefore, modular designs on a sliding foundation have been developed which significantly reduce the energy required to make up the connection as well as facilitate maintenance and repair.

This paper describes the design aspects of large deepwater PLEM and the methodology which has lead to feasible solutions in 300m to 1300m water depths. Potential cost savings are related to successfully perfoming the subsea tie-ins using smaller subsea construction vessels. The deepwater connections become increasingly expensive for larger diameter pipelines if the risks are not reduced by the design and by performing advanced engineering involving finite element analysis (FEA).
Comparison of Mooring Loads in Survivability Mode on the Wave Dragon Wave Energy Converter Obtained by a Numerical Model and Experimental Data
Authors: Parmeggiani Stefano , Muliawan Made Jaya , Gao Zhen , Moan Torgeir , Friis-Madsen Erik
Published: August 2013

The Wave Dragon Wave Energy Converter is ready to be up-scaled to commercial size. The design and feasibility analysis of a 1.5 MW pre-commercial unit to be deployed at the DanWEC test center in Hanstholm, Denmark, is currently ongoing. With regard to the mooring system, the design has to be carried out numerically, through coupled analyses of alternative solutions. The present study deals with the preliminary hydrodynamic characterization of Wave Dragon needed in order to calibrate the numerical model to be used for the mooring design. A hydrodynamic analysis of the small scale model in the frequency domain is performed by the software HydroD, which uses WAMIT as core software. The quadratic damping term, accounting for the viscous effect, is determined through an iterative procedure aimed at matching numerical predictions on the mooring tension, derived through time domain coupled analysis, with experimental results derived from tank tests of a small scale model. Due to the complex geometry of the device, a sensitivity analysis is performed to discuss the influence of the mean position on the quality of the numerical predictions. Good correspondence is achieved between the experimental and numerical model. The numerical model is hence considered reliable for future design applications.
Fully Coupled Time Domain Modelling of 3D Floating Bodies and Mooring Systems in Regular and Irregular Sea States
Authors: Vepa Kameswara S. , Van Nuffel Diederik , Van Paepegem Wim , Degrieck Joris
Published: August 2013

Research on floating bodies like Wave Energy Converters (WECs) and Laser Imaging Detection And Ranging (LIDAR) systems has recently known a large growth. To study the minute details of the working model, it is important to study the effect of interactions between the waves, floating bodies and the mooring systems that are controlling the motion of the floating body. To achieve a more realistic numerical model in the time domain, a number of programs are linked together. The idea is to use the strength of each individual program for better results and also reduce the computational time.

This paper provides a solution in the direction of using a fully coupled time domain coupling code that controls the data flow between a fluid solver, a structural solver, and a kinematic system simulator.

Two- and three-dimensional fully coupled models are studied for calculation times and accuracy of results, and scaling is tested through parallelization on a large HPC cluster. The time step size of the whole model can be controlled by the user. Calculation times and memory requirements vary largely based on the factors like: domain size, SPH particle size, material model used for the floating body and the mooring system, complexity of the mechanical system inside the floating body. As a test case, a rigid body model is presented in this paper.
Modeling the Dual Crane Lift of Maersk BD Module
Authors: Aboumalwa Mohamed , Joe-Joe Chellakat , Nair Sajith
Published: August 2013

McDermott Middle East, Inc. executed the Maersk Oil Qatar Project in 2009, Offshore Qatar. The project involved the installation of one of the heaviest lifts in the region — the 3283 MT BD Module. The deciding factor for the offshore installation methodology was the restriction on the lift capacity of the derrick barge. The execution strategy, therefore, involved utilizing two derrick barges, a semi-submersible and a mono hull barge, in tandem for the lift operation (Dual Lift). This paper discusses the engineering studies and the simulation model for a Dual Lift with insight into the technical complexities and the analytical strategy used for the study.

On site adherence to the engineering analyses was achieved by a system of pre-installed motion sensors and instruments capable of delivering real time data of the key parameters required for the lift. The engineering and operations experience presented in this paper covers the Dual Lift operation with focusing on two main engineering aspects, the engineered lift study of BD Module and the multi-body mooring analysis compromising six floating bodies connected together by means of lashing and/or mooring lines.