bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Study for the Effect of Appendages on Vortex-Induced Motions of Tension Leg Platform
Authors: Tian Chenling , Liu Mingyue , Wang Shisheng , Wang Xinru , Li Haobo 
Published: September 2018

Vortex-induced motions (VIM) of large marine structures have been emerged as hot issues both in engineering and academic fields. Aiming to investigate the effect of the appendages on the VIM phenomenon of the tension leg platforms (TLP), experimental studies were carried out in a towing tank., The tendon pretensions and mass ratio were modeled exactly by using an air-bearing system. Additionally, the motions in vertical plane were almost restricted and the TLP model was allowed to move freely in horizontal plane. The 6-degrees of freedom (6-DOF) motions of the model were recorded by the motion acquisition system, consistent with an acceleration sensor installed at the deck as well as four load cells employed to acquire the restoring forces of the four mooring lines respectively.
This paper presents the VIM responses of the TLP model with bare hull and the model with appendages located at the surface of columns with different relative positions to the current (i.e., 0°, 45°, 90° and 135°, respectively). In addition, the dynamic behaviors are also processed. The results show that the amplitudes of VIM response in the transverse direction are mitigated significantly for the configuration of 45°-appendages, lower than that of the bare hull model about 65 percent but slightly subsided at other locations. Moreover, the appendages at all locations can obviously reduce the amplitudes of the yaw motions, with the maximum decrease of 52 percent of the yaw responses for the configuration of 0°-appendages and 45°-appendages, compared with that of the bare hull model.
Simplified FEA Models in the Analysis of the Redistribution of Beneficial Compressive Stresses in Welds During Cyclic Loading
Authors: Josefson B. L. , Alm J. , McDill J. M. J. 
Published: September 2018

The fatigue life of welded joints can be improved by modifying the weld toe geometry or by inducing beneficial compressive residual stresses in the weld. However, in the second case, the induced compressive residual stresses may relax when the welded joint is subjected to cyclic loading containing high tensile or compressive stress peaks.
The stability of induced compressive stresses is investigated for a longitudinal gusset made of a S355 steel. Two methods are considered; either carrying out a high frequency mechanical impact (HFMI) treatment after welding or alternatively using low transformation temperature (LTT) electrodes during welding. The specimen is then subjected to a cyclic loading case with one cycle with a tensile peak (with magnitude reaching the local yield stress level) followed by cycles with constant amplitude. A sequential finite element analysis (FEA) is performed thereby preserving the history of the elasto-plastic behavior. Both the welding process and the HFMI treatment are simulated using simplified approaches, i.e., the welding process is simulated by applying a simplified thermal cycle while the HFMI treatment is simulated by a quasi-static contact analysis.
It is shown that using the simplified approaches to modelling both the welding process and HFMI treatment gives results that correlate qualitatively well with the experimental and FEA data available in the literature. Thus, for comparison purposes, simplified models may be sufficient. Both the use of the HFMI treatment and LTT electrodes give approximately the same compressive stress at the weld toe but the extent of the compressive stress zone is deeper for HFMI case.
During cyclic loading it is shown that the beneficial effect of both methods will be substantially reduced if the test specimen is subjected to unexpected peak loads. For the chosen load sequence, with the same maximum local stress at the weld toe, the differences in stress curves of the HFMI-treated specimen and that with LTT electrodes remain. While the LTT electrode gives the lowest (compressive) stress right at the well toe, it is shown that the overall effect of the HFMI treatment is more beneficial.
Trajectory Control of a Tethered Underwater Robot System
Authors: Wu Jiaming , Chen Dongjun , Xu Ying , Chen Yuqing , Lu Lihua 
Published: September 2018

A three-dimensional hydrodynamic and control model to simulate tethered underwater robot system is proposed. The fluid motion around the moving robot main body with running control ducted propellers is governed by Navier-Stokes equations, and multiple sliding mesh technique is applied to solve the governing equations. The governing equation of umbilical cable connected to the robot is based on the Ablow and Schechter method. The six-degrees-of-freedom equations of motion for underwater vehicle simulations proposed by Gertler and Hargen are adopted to estimate the hydrodynamic performance of the underwater robot. In the model, the feed-forward control algorithm is applied to adjust the length of the umbilical cable according to the robot trajectory control target, the incremental PID control algorithm is adopt to regulate the rotating speeds of the ducted propellers producing appropriate thrusts for the robot control. With the proposed hydrodynamic and control model, hydrodynamic behaviors of the robot under definite trajectory control manipulations are observed numerically.
The numerical results of robot trajectory control simulations indicate that the feed-forward control algorithm for adjusting the length of the umbilical cable, and the incremental PID control algorithm for regulating the rotating speeds of the propellers are feasible and effective, the adjusting the length of the umbilical cable with feed-forward control technique is largely responsible for the vertical trajectory control to the robot, while regulating the rotating speeds of the propellers by the PID control algorithm play a leading role in the horizontal trajectory manipulation, the deviation between the designated trajectory and the control one at each time step is acceptable.
Advanced FE Modelling Approach for Pipeline Hooking Interaction of Dragged Anchors
Authors: Bartolini Lorenzo , Marchionni Lorenzo , Parrella Antonio , Vitali Luigino 
Published: September 2018

Offshore pipelines, located in areas with high/medium ship traffic, are exposed to threats such as dragged anchors, dropped objects, sinking ships, etc..
In the last years, there have been a few accidents where subsea pipelines or cables have been hooked and damaged by dragged anchors. These incidents have been caused both by emergency and accidentally dragged anchors. Two of the most serious incidents to pipelines caused by an accidentally dragged anchor involved the Trans Mediterranean gas pipelines in 2008 and the Kvitebjørn gas pipeline in the North Sea in 2007.
The interaction mechanism between the pipeline and an anchor dragging on the seafloor is affected by different parameters (i.e. anchor size, chain length, water depth, soils geo-technics, anchor speed, incident angle between the pipeline and the anchor dragging direction). In common practice, the occurrence of hooking events is assessed by implementing specified interpretative model involving basically typical anchor dimensions for the different ship classes and expected soil pipe interaction scenarios.
Major efforts have been made to develop a 3D Finite Element model with the aim of improving the simulation capabilities of engineers to address and anticipate the mechanism of pipeline and dragged anchor interaction. The model presented in this paper is based on the Coupled Eulerian Lagrangian (CEL) technique. With respect to typical simplified FE models, implementing the seabed as an analytic surface, this advanced technique (i.e. CEL) allows one to model the seabed as a deformable Eulerian domain, in which the anchor (and the pipeline) can penetrate. The seabed settlement and the displacement of soil particles due to anchor motion can be fully calculated.
The FE Model includes the steel pipeline geometry and the external concrete coating, the surrounding water, the deformable seabed and the 3D anchor geometry with its chain.
Scope of this assessment is to improve the understanding of the pipeline and anchor interaction event. In particular the focus is on the mechanisms and dynamics of accidental events which lead to the occurrence of anchor engagement with the pipeline. Eventually, the final goal is to refine and take into due account the contribution of accidentally dragged anchor scenario in the overall procedure for pipeline design against threats posed by commercial ship traffic.
In this paper:
• The state of the art about the classical analysis methodology recommended by standards to evaluate the interaction between the pipeline and the accidental dragged anchors is briefly described;
• A FEM based analysis methodology is drawn and proposed to address the potential for pipeline hooking by the accidentally dragged anchor event;
• A typical application is presented.
Crashworthiness Assessment of Thin-Walled Bottom Structures During Powered-Hard Grounding Accidents
Authors: Prabowo Aditya Rio , Sohn Jung Min , Bae Dong Myung , Setiyawan Agus 
Published: September 2018

Advance development in engineering and technology has been massively triggered by establishment of the free market memorandum between countries across the globe. Explicitly, this agreement affects ship and offshore industries, where stakeholder and investor demand a wide range of accidental damage assessment. Achievement of this objective is highly influenced by sustainable research on maritime accidents. Ship grounding is categorized in impact phenomena, and record has evidenced grounding as the most risky accident. Since it is capable to evoke massive losses, estimation of structural performance and limit under grounding is required.
This work aims to evaluate crashworthiness of a thin-walled tanker structures in encountering ship grounding. A series of benchmark simulations based on pioneer experimental test is re-performed as calibration of numerical configuration for grounding analysis. Several scenarios are designed in this stage by varying mesh sizes on the idealized test geometry. Preparation for the grounding analysis is presented in the next stage. Considering its characteristic as impact load, powered-hard scenario is taken into account as the worst possible damage on the structures. It is assumed that grounding happens suddenly when the tanker is in a voyage and interacts with a hard object. A medium-carbon steel is embedded with the Det Norske Veritas - Germanischer Lloyd (DNVGL) fracture criterion. In this study, an oceanic obstruction is defined as seabed reef geometry with the properties are adopted based on data of ocean crustal seismology. Varieties of location, angle and elevation are applied to accidental grounding scenarios. The assessment of structural crashworthiness brings an insight into the effect sensitivity of the parameters on the double bottom behavior. Brief recommendation for grounding simulation is provided in final conclusion to give adequate references in applying numerical input and configuration, especially using the finite element (FE) method.
Investigation on the Shooting Method Ability to Solve Different Mooring Lines Boundary Condition Types
Authors: Surmont Florian , Coache Damien 
Published: September 2018

The study of undersea cables and mooring lines statics remains an unavoidable subject of simulation in offshore field for either steady-state analysis or dynamic simulation initialization. Whether the study concerns mooring systems pinned both at seabed and floating platform, cables towed by a moving underwater system or when special links such as stiffeners are needed, the ability to model every combination is a key point.
To do so the authors propose to investigate the use of the shooting method to solve the two point boundary value problem (TPBVP) associated with Dirichlet, Robin or mixed boundary conditions representing respectively, displacement, force and force/displacement boundary conditions.
3D nonlinear static string calculations are confronted to a semi-analytic formulation established from the catenary closed form equations. The comparisons are performed on various pairs of boundary conditions developed in five configurations.
Large Scale Physical Modelling for a Floating Concrete Caisson in Marine Works
Authors: Meneses Lucía , Sarmiento Javier , de los Dolores Daniel , Blanco David , Guanche Raúl , Losada Íñigo J. , Rodriguez de Segovia María F. , Ruiz Manuel J. , Martín Miguel A. , Conde María J. , Esteban Francisco 
Published: September 2018

In the last years, the use of floating concrete caissons in coastal infrastructures has been generalized: docking structures, vertical breakwater and special floating structures. In this field, one of the most important and less analyzed stages of the marine works is the sinking process of the floating caissons.
The test campaign presented in this work is innovative in scale (1:12) and includes an analysis of the different stages of a floating caisson during its life cycle: detached concrete caisson, caisson positioning and sinking and berthed floating caisson, resulting in more than 130 tests performed. Movements and tensions have been analyzed for a wide array of sea states and different configurations of mooring systems and horizontal layouts.
A new tool for dynamic positioning control was designed and developed as part of the test campaign. The design of this tool has led to the development of a specific numerical model that reproduced the dynamic behavior during sinking. The dynamic positioning control was implemented in the physical model campaign, which has meant an important advance in the construction process of maritime infrastructures.
Moreover, the campaign carried out has allowed the validation and calibration of the tools developed, allowing all the work to reduce costs and increase the safety of these types of marine operations.
MAESTRALE: The Implementation of Blue Energy in the Mediterranean Sea
Authors: Abanades Javier , Torregrosa Juan Pablo 
Published: September 2018

The project Maestrale is an European Project funded by the Interreg MED programme (2016–2019) that aims at establishing the basis for a Maritime Energy Deployment Strategy in the Mediterranean Sea. The project is formed by a consortium with partners around the South of Europe with the objective of determining a suite of pilot zones, which will become the pillars of future developments for the implementation of Blue Energy projects in the Mediterranean Sea.
The present article presents the tasks to be conducted for the study of the area in the Spanish Mediterranean Arc:
• Identification of recommendations and regulations
• A benchmark of the technologies installed worldwide will be carried out in order to identify their degree of adaptability to the conditions of the Med Area
• The analysis of the available resource: wind, wave and tidal
• The study of the area and its features: bathymetry, land cover, protected areas, etc.
• The identification of the stakeholders, as the project intends to strengthen cooperation between public authorities, research bodies, businesses and the civil society
• The formation of clusters with the stakeholders, either at the national or trans-national level, to increase connections in order to promote knowledge and technological transfer and generate the critical mass and environmental conditions needed to improve innovation capacities and competitiveness
The main outcomes of the project are the support of the future blue energy policies and concrete strategies for blue growth and a suite of pilot projects that will serve the purpose of raising awareness among local stakeholders, facilitating social acceptance, decreasing uncertainty and increasing feasibility of concrete interventions.
An Analysis on the Change of Ship Speed According to Ice Load Signal in Continuous Icebreaking and Ramming
Authors: Ahn Se-Jin , An Woo-Seong , Lee Tak-Kee , Choi Kyungsik 
Published: September 2018

Recently, the research activities by domestic and overseas researchers using the Korean ice-breaking research vessel, ARAON have been actively conducted. The ARAON regularly operates for research activities in the Antarctic and the Arctic Ocean every year. She conducts many scientific and engineering tasks including ice load measurement, investigation of the properties of material strength for sea ice, and icebreaking performance test during her voyages. Such tests provide important data for studying icebreaker.
Ice-breaking mode is determined by conditions of sea ice and ice field, and it is divided into ramming and continuous icebreaking. When the icebreaker meets thick ice or icebergs, the ramming is conducted. At that time, the ship speed is generally slower than that of the continuous icebreaking. The ARAON conducted icebreaking performance tests at the Amundsen Sea in Antarctica in 2012. Many strain data were measured in the ramming and the continuous icebreaking.
This study was based on the strain gauge signals measured by the ARAON during the research voyage in 2012 in the Antarctic and 2010 in the Arctic. The signals measured from repetitive ramming under the heavy ice condition in 2012 in the Antarctic Ocean were classified into the five profiles. And the classified ice load signals were analyzed with a focus on raising time, half-decaying time and total time duration. Also, the signals measured from continuous icebreaking in 2010 in the Arctic Ocean were analyzed in the same way as the ramming data. Finally, the time histories of ice load signals were summarized from the viewpoint of speed change at the time of ice load, and two data sets were compared.
Application of GPGPU to Accelerate CFD Simulation
Authors: Mintu Shafiul A. , Molyneux David 
Published: September 2018

Computational Fluid Dynamics (CFD) is widely used in industry and academic research to investigate complex fluid flow. The bottleneck of a realistic CFD simulation is its long simulation time. The simulation time is generally reduced by massively parallel Central Processing Unit (CPU) clusters, which are very expensive. In this paper, it is shown that the CFD simulation can be accelerated significantly by a novel hardware called General Purpose Computing on Graphical Processing Units (GPGPU). GPGPU is a cost-effective computing cluster, which uses the Compute Unified Device Architecture (CUDA) of NVIDIA devices to transform the GPU into a massively parallel processor.
The paper demonstrates the faster computing ability of GPU compared to a traditional multi-core CPU. Two scenarios are simulated; one is a 2-dimensional simulation of regular wave and another one is a 3-dimensional motion of a floating ship on a regular wave. A smoothed particle hydrodynamics (SPH) based CFD solver is used for simulating the complex free-surface flow. The performance of a single GPU is compared against a commonly used 16 core CPU. For a large simulation of 6 degrees of freedom (DOF) ship motion simulation, the comparative study exhibits a speedup of more than an order of magnitude, reducing simulation time from 30 hours to about 2 hours. This indicates a CUDA enabled GPU card can be used as a cost-effective computing tool for a reliable and accurate SPH-based CFD simulation. The cost-benefit analysis of GPU over a CPU cluster is also discussed.
Modeling of a Semisubmersible Floating Wind Platform in Severe Waves
Authors: Rivera-Arreba I. , Bruinsma N. , Bachynski E. E. , Viré A. , Paulsen B. T. , Jacobsen N. G. 
Published: September 2018

Floating offshore wind platforms may be subjected to severe sea states, which include both steep and long waves. The hydrodynamic models used in the offshore industry are typically based on potential-flow theory, and/or Morison’s equation. These methods are computationally efficient, and can be applied in global dynamic analysis considering wind loads and mooring system dynamics. However, they may not capture important nonlinearities in extreme situations. The present work compares a fully nonlinear wave tank (NWT), based on the viscous Navier-Stokes equations, and a second-order potential-flow model for such situations.
A validation of the NWT is first completed for a moored vertical floating cylinder. The OC5-semisubmersible floating platform is then modelled numerically both in this nonlinear NWT and using a second-order potential-flow based solver. To validate both models, they are subjected to non-steep waves and the response in heave and pitch is compared to experimental data.
More extreme conditions are examined with both models. Their comparison shows that if the structure is excited at its heave natural frequency, the dependence of the response in heave on the wave height and the viscous effects cannot be captured by the adjusted potential-flow based model. However, closer to the inertia-dominated region, the two models yield similar responses in pitch and heave.
New Generation of Heavy Wall Thicknesses Line Pipes for HPHT and Ultra-Deep Water Applications
Authors: Crippa Stefano , Motta Lorenzo , Paggi Alessandro , Bagliani Emanuele Paravicini , Elitropi Alessandro , Darcis Philippe 
Published: September 2018

Oil and Gas industry in the last decades has increased the use and need of heavy wall thickness line pipes, in particular for onshore / offshore high pressures and high temperatures (HP/HT) and offshore deep water / ultra-deep water applications.
The paper presents the results achieved by Tenaris on seamless line pipes in grades X65/X70, according to API 5L / ISO 3183, with wall thickness in a range from 40 to 60 mm and diameter between 6 5/8” and 16”, produced by hot rolling process followed by quenching and tempering. Such line pipes are able to withstand very demanding conditions, like sour environment, very high pressure and wide temperature range.
In this publication, the main outcomes of laboratory testing activities on the mentioned materials will be presented as part of heavy wall line pipe qualification. For this purpose, a special testing program, including mechanical and corrosion tests, has been executed. Material demonstrated an excellent behaviour, exhibiting both mechanical, toughness and stress corrosion properties suitable for the envisaged harsh applications.
A Methodology to Characterize Internal Solitons in the Ocean
Authors: Coelho Henrique , Peng Zhong , Sproson Dave , Bradon Jill 
Published: September 2018

Internal waves in the ocean occur in stably stratified fluids when a water parcel is vertically displaced by some external forcing and is restored by buoyancy forces. A specific case of such internal waves is internal tides and their associated currents. These currents can be significant in areas where internal waves degenerate into nonlinear solitary waves, known as solitons.
Solitons are potentially hazardous for offshore engineering constructions, such as oil/gas pipelines and floating platforms. The most efficient mechanism of soliton generation is the tidal energy conversion from barotropic to baroclinic component over large-scale oceanic bottom obstructions (shelf breaks, seamounts, canyons and ridges).
In this paper, a methodology is provided to compute diagnostics and prognostics for soliton generation and propagation, including the associated currents. The methodology comprises a diagnostic tool which, through the use of a set of theoretical and empirical formulations, selects areas where solitons are likely to occur. These theoretical and empirical formulations include the computation of the integral body force (1), the linear wave theory to compute the phase speed and the empirical model proposed by (2). After the selection procedure, the tool provides initial and boundary conditions for non-hydrostatic numerical models. The numerical models run in 2D-V configuration (vertical slices) with horizontal and vertical resolutions ranging from 50 to 200 m and 5 to 10 m, respectively. Examples are provided for an open ocean location over the Mascarene Plateau in the Indian Ocean. Validation of diagnostics and prognostics are provided against ADCP and satellite data.