bluuebunny/crossref_metadata_2025_split huggingface dataset:
CFD Parametric Study of Geometrical Variations on the Vortex-Induced Motions of Deep-Draft Semi-Submersibles
Authors: Zhao Weiwen , Wan Decheng 
Published: September 2018

Vortex-Induced Motions (VIM) is a key issue for deep draft column stabilized floaters (DDCSF). An example of DDCSF is the concept design called Paired-Column semi-submersible (PC-Semi) with a pair of columns instead of single column at four corners of the platforms. The complex multi-column design involves several extra design parameters such as paired-column gaps and column cross-section areas than conventional semi-submersibles. These parameters can be tuned to mitigate dynamic response to waves and currents. However, it is expensive to perform parametric study of geometric variations by means of experiments.
In the present work, CFD method is utilized to investigate the VIM characteristics for different geometrical variations of the PC-Semi. An in-house CFD code naoe-FOAM-SJTU, which is developed on top of the open source framework OpenFOAM, is used for all numerical simulations. Delayed detached-eddy simulation (DDES) is used for turbulence modeling with massively separated flow. A geometry model scaled at 1:54 from MARIN is select as the baseline model for parametric study. VIM simulations of the baseline model is firstly carried out and compared with experiments to validate the current CFD code. After that, VIM characteristics of paired-column gaps geometrical variations are numerically investigated. Motions of the platform and hydrodynamic forces on columns are compared and analyzed. The ability of CFD method in optimizing geometric design parameters on mitigating VIM response for deep-draft semi-submersibles is demonstrated.
Buckling of Stiffened Panels: An Improved Linearized Approach Compared to Nonlinear Collapse Analysis
Authors: Gaiotti Marco , Rizzo Cesare Mario , Ferrari Nicole , Montella Adriano 
Published: September 2018

This paper deals with the buckling assessment of stiffened panels, typical of ship and offshore structures. In particular, rather slender structures, involving very thin plates and stiffeners with limited cross section, are considered.
In order to limit the computational burden of a fully nonlinear progressive collapse analysis but, at the same time, to retain some benefits of a numerical finite element model assessment, an improved linearized buckling procedure is proposed in this work. The idea is to linearize the computation in a suitable point based on the design load of the structure, so that the results of a linearized buckling analysis are more informative in practice. Results are assessed with nonlinear collapse analyses, comprehensively considering various loading cases. Eventually, a hands-on buckling assessment procedure is suggested, which can be implemented in rules and design process if adequately validated by a suitable number of test cases and, possibly, experimental data.
The Study on Design and Ice Collision of Icebreaking Tanker
Authors: Jang Youngjae , Park June , Lim Wooram , Kim Hanbyul , Won Sunil , Park Yunki 
Published: September 2018

52,000 deadweight ton class icebreaking tanker is designed to comply with Russia Maritime Register of Shipping(RMRS) ice category Arc7 and IACS CSR-H.
The ice breaking load was obtained from the DDePS of the ABS Classification Society and the limit load calculation was examined through the Abaqus nonlinear analysis.
The collision location and iceberg type selection were adopted to define iceberg-hull collision scenarios. Nonlinear analysis simulated ice breaking process by using LS-DYNA.
Implementing Human Factors in Oil and Gas Drilling and Completion Operations: Enhancing Culture of Process Safety
Authors: Kiran Raj , Salehi Saeed , Teodoriu Catalin 
Published: September 2018

The role of Human Factors, in complex environments like the oil and gas industry, has seen a paradigm shift over a very short span of time recently. Past studies have limited focus on the human system interfacial approach. However, the repeated failures have forced the industry and academia to take a closer look at the cascading failures with human errors perspective and conduct the root-cause analysis from the cognitive aspect. Traditionally, the knowledge, expertize, and competence took the driving seat while the human factors had been on the back burner. Lack of emphasis on Human Factors in academic research could be another reason for this laxity. Consideration of human factors in the design of systems is centered on the end user. Systems are designed to fit the physiological limitations of the people tasked with managing them. The design includes features that improve comfort and productivity, minimize errors, and minimize training time.
In this paper, first a review of crucial human factors in different well cycles such as drilling, well completion, fracturing, and abandonment will be presented. Through various cases studies, it will be shown that potential challenges can be mitigated with proper implementation of various elements for human factors such as situational awareness, team working, stress management and other non-technical skills. In addition, this paper reviews the critical components and perceived gaps of existing safety management systems in use as well as those elements that would be of most value to drilling taken from other sectors or industries on a ‘first principles’ basis. The paper attempts to highlight ’the myths, misconceptions, and realities of complex well operations’ that either deter changes or demand a new approach. It is the authors premise that if either a ‘clean sheet’ approach or more ‘actual cost’ weight was given to both common problems and low probability high consequence events such as kicks or loss of well control.
Effect of Surface Curvature on the Hydrodynamics of Water Entry at High Horizontal Velocity
Authors: Iafrati Alessandro 
Published: September 2018

The role played by the curvature of the body surface on the hydrodynamics of water entry with high horizontal velocity component is investigated experimentally. The study is a part of a research activity finalized at the understanding of the aircraft ditching problem. In order to avoid scaling effects which may prevent the development of ventilation/cavitation phenomena, the study is carried out at full scale velocity. Measurements are presented in terms of pressures and loads whereas some underwater visualizations are used for the interpretation of the data. Both a convex and concave body surface are considered and comparisons with the flat plate data are established.
In the case of a concave shape, a quite complicated flow with large air entrainment develops beneath the plate. The air entrainment causes a general reduction of the pressure peak at the middle, whereas the pressure peaks recorded at the side probes are about in line with those found for the flat plate in the same conditions. The total hydrodynamic load acting normal to the plate grows more regularly but the maximum load is essentially the same as that measured in the flat plate case. For the convex shape, the pressure probes located in the middle of the plate get wetted well before the ones at the side and the pressure peaks at the sides are much lower than those in the middle. The reduced pressures at the sides cause a reduction of the total loading in the normal direction compared to flat and concave plates.
Remaining Life Assessment and Life Extension of Offshore Pipelines
Authors: Tronskar Jens P. 
Published: September 2018

Cost efficient offshore field development often involves tiebacks to existing field infrastructure. Efficient field development requires life extension of existing production facilities and pipelines to accommodate the new field resources over their life expectation. For fields near the tail end of their production the pipelines may be close to the end of their design life, and it must be shown that they have potential for extended life beyond the original design life until the end of the period of operation of the new field.
Offshore pipelines are designed and constructed to recognized standards, such as the widely applied DNV OS-F101 2013 Submarine Pipelines Systems and earlier versions. The latest edition of the code was recently issued as a standard with some major updates and a modified code number i.e. DNVGL ST-F101 [1].
As pipelines age, they will inevitably be exposed to various types of degradation and an Operator must be able to both assess the significance of this damage and the pipeline remaining life to ensure that the pipelines do not fail as they age before the end of their design lives. Currently, many pipelines are operated far beyond the original design life and as mentioned above for cost efficient field development the pipeline operator often needs to demonstrate that the pipeline’s useful life can be extended another 10 or in some cases up to 30 years. For some pipelines, new operating conditions will be introduced by tie-in of new fields and this will impact the future rate of degradation. Hence, it cannot be assumed that the future degradation will be similar or less severe than experienced since commissioning of the pipeline.
Extension of the life of the pipeline can be demonstrated by adopting methods of analysis that show the line is safe for an extended life under the future expected operating condition.
This paper describes the risk based approach applied for pipeline remaining life and life extension analyses based on DNV GL codes and other relevant recommended practices. For illustration of the methodology a typical case of remaining life assessment of and life extension of a gas export pipeline is presented in the Case Study.
Simulator for Arctic Marine Structures (SAMS)
Authors: Lubbad Raed , Løset Sveinung , Lu Wenjun , Tsarau Andrei , van den Berg Marnix 
Published: September 2018

As offshore activities in the Arctic constitute a relatively new field with only a handful of relevant operations to draw experience from, and since full-scale trials are extremely expensive, there is an expressed need for much more extensive, detailed and cost-efficient analysis of concepts based on numerical simulations. However, until recently simulation tools of sufficient quality to perform such numerical analysis have not existed. The only verification available has been through a limited set of experiments in ice model basins. Today, this has changed, partly through the efforts at the Norwegian University of Science and Technology (NTNU) hosting SAMCoT (Centre for Research-based Innovation - Sustainable Arctic Marine and Coastal Technology), laying the foundation of a versatile and highly accurate high-fidelity numerical simulator for offshore structures in various ice conditions such as level ice, broken ice and ice ridges.
Arctic Integrated Solutions AS (ArcISo) is a spin-off company from NTNU established in 2016 with the vision of increasing the technology readiness level of SAMCoT’s numerical models to become a professional software package for the analysis of sea ice actions and action effects on Arctic offshore and coastal structures. This software package is called Simulator for Arctic Marine Structures (SAMS) and it was first released in 2017. This paper introduces the software implementation and the theoretical basis of SAMS, and it discusses the use of full-scale data to validate the simulator.
Modelling Results With a New Simulator for Arctic Marine Structures - SAMS
Authors: Tsarau Andrei , van den Berg Marnix , Lu Wenjun , Lubbad Raed , Løset Sveinung 
Published: September 2018

The Simulator for Arctic Marine Structures (SAMS) has emerged on the foundation of a number of scientific models developed at SAMCoT – Centre for Research-based Innovation - Sustainable Arctic Marine and Coastal Technology hosted by NTNU – as a versatile numerical tool for the analysis of sea ice actions and action effects on Arctic offshore structures. The current capabilities of SAMS allow engineers to analyse icefloe impacts and ice loads on arbitrary marine structures in various environmental conditions; simulations may involve both fixed and floating structures, non-rigid multi floe interactions, ice breaking and ice rubbling, wind, current and propeller-flow effects on both structures and ice. All these capabilities can be combined to model also complex marine operations in the Arctic and subarctic regions.
As SAMS can be applied in both full- and model scales, a number of available experimental case studies from the field and ice tanks can be reanalysed with the new simulator to ensure the high fidelity of the simulations and to establish a validation basis. This paper presents several of such case studies and discusses further validation possibilities.
Validation Exercises for a Free Falling Wedge Into Calm Water
Authors: Muralha João , Eça Luís , Maximiano António , Vaz Guilherme 
Published: September 2018

This paper presents the assessment of the modelling error (Validation) of a Navier-Stokes solver using Volume of Fluid (VOF) and moving grid techniques in the simulation of a free falling wedge into calm water. This problem has been studied experimentally to determine the time histories of six pressure probes located on the wedge surface and the acceleration of the wedge. The simulation is restricted to the first 100ms after the impact of the wedge on the water (t = 0 at the impact) and the mathematical model uses the following assumptions: incompressible fluid; two-dimensional, laminar flow, negligible shear-stress at the surface of the wedge and deep water. The selected quantities of interest are the peak pressures at the six sensors, time intervals between peak pressures at the sensors, sensors pressures and acceleration of the wedge at six different time instants and integrated pressure signals for 80ms after the pressure peak at the first sensor.
The application of the ASME V&V 20 standard to local quantities is presented, including the estimation of experimental and numerical uncertainties. Furthermore, a multivariate metric is used to evaluate quantitatively the overall performance of the mathematical model. The results show significant comparison errors (mismatches between simulations and measurements) for the accelerations, which may be a consequence of the assumptions of a deep water boundary condition at the bottom. However, such conclusion is hampered by some doubts about the accuracy of the experimental data. On the other hand, modeling errors are significantly smaller for the pressure measurements at the six sensors for which the main challenge is to reduce the validation uncertainty Uval. In many of the selected flow quantities, Uval is dominated by the experimental uncertainty.
Full-Scale Reynolds Number VIV Testing of Tri-Helically Grooved Drill Riser Buoyancy Module
Authors: Gaskill Collin , Wu Jie , Yin Decao 
Published: September 2018

A newly developed Tri-Helically Grooved drilling riser buoyancy module design was tested in the towing tank of SINTEF Ocean in June 2017. This new design aims to reduce riser drag loading and suppress vortex-induced vibrations (VIV). Objectives of the test program were two-fold: to assess the hydrodynamic performance of the design allowing for validation of previous computational fluid dynamics (CFD) studies through empirical measurements, and, to develop a hydrodynamic force coefficient database to be used in numerical simulations to evaluate drilling riser deformation due to drag loading and fatigue lives when subjected to VIV.
This paper provides the parameters of the testing program and a discussion of the results from the various testing configurations assessed.
Tests were performed using large scale, rigid cylinder test models at Reynolds numbers in the super-critical flow regime, defined as starting at a Reynolds number of Re = 3.5 × 105 – 5.0 × 105 (depending on various literatures) and continuing until Re = 3 × 106. Towing tests, with fixed and freely oscillating test models, were completed with both a bare test cylinder and a test cylinder with the Tri-Helical Groove design. Additional forced motion tests were performed on the helically grooved model to calculate lift and added mass coefficients at various amplitudes and frequencies of oscillation for the generation of a hydrodynamic force coefficient database for VIV prediction software.
Significant differences were observed in the hydrodynamic performance of the bare and helically grooved test models considering both in-line (IL) drag and cross-flow (CF) cylinder excitation and oscillation amplitude. For the helically grooved model, measured static drag shows a strong independence from Reynolds number and elimination of the drag crisis region with an average drag coefficient of 0.63.
Effective elimination of VIV and subsequent drag amplification was observed at relatively higher reduced velocities, where the bare test model shows a significant dynamic response. A small level of expected response for the helically grooved model was seen across the lower range of reduced velocities. However, disruption of vortex correlation still occurs in this range and non-sinusoidal and highly amplitude-modulated responses were observed.
Background and New Revision of DNVGL-RP-F108
Authors: Lindberg Bjerke Steinar , Tronskar Jens P. , Chong Steven , Venås Asle 
Published: September 2018

DNV-RP-F108 [1] was first issued in 2006. The Recommended Practice was developed to provide guidance on testing and analyses for fracture control of pipeline girth welds subjected to cyclic plastic deformation, e.g. during installation by the reeling method, but also for other situations where pipelines may be subjected to large plastic strains. The Recommended Practice was based upon a Project Guideline developed within the Joint Industry Project “Fracture Control for Installation Methods Introducing Cyclic Plastic Strain - Development of Guidelines for Reeling of Pipelines”.
The new revision is based on the extensive experience and knowledge gained over the years use of the previous versions, as well as new knowledge from recent R&D projects.
The main content of Appendix A of DNV-OS-F101 (now DNVGL-ST-F101) [2] have been transferred to DNVGL-RP-F108. Only the requirements relative to ECA and testing have been retained in DNVGL-ST-F101 [2].
The new revision has got a new number and new title, i.e. DNVGL-RP-F108, “Assessment of Flaws in Pipeline and Riser Girth Welds”.
This paper lists the fundamental changes made in the new RP from the old Appendix A of the previous DNV-OS-F101 and discusses some of the changes, although within this paper it is not possible to cover all changes. The focus is on clarification of use of S-N versus the fracture mechanics approach for fatigue life computation, classification of fatigue sensitive welds, calculations of more accurate crack driving force by re-introduction of the plate solution, for which a new Lr,max (plastic collapse) calculation and a modified way to account for residual stresses have been specified. The RP presents new assessment procedures pertaining to use of finite element analyses for fracture mechanics assessments. A unique feature of the new RP is the guidance on sour service testing and assessments included in the Appendix C of the document to support pipeline/riser ECAs to develop flaw acceptance criteria for NDT.
Laboratory Set-Up for Determination of Cement Sheath Integrity During Pressure Cycling
Authors: Skorpa Ragnhild , Øia Thomas , Taghipour Ali , Vrålstad Torbjørn 
Published: September 2018

The annular cement sheath is one of the most important well barrier elements, both during production and after well abandonment. It is however well-known that repeated pressure and temperature variations in the wellbore during production and injection can have a detrimental effect on the integrity of the cement sheath. Degradation of cement sheaths result in formation of cracks and microannuli, which leads to loss of zonal isolation and subsequent pressure build-up in the annulus. It is therefore important to study and understand cement sheath failure mechanisms to prevent such barrier failures.
A unique laboratory set-up with downscaled samples of rock, cement and pipe has been constructed to study cement sheath failure mechanisms such as radial crack formation and debonding during pressure cycling. Cement integrity before and after pressure cycling is monitored by X-ray computed tomography (CT), which enables 3D visualization and quantification of radial cracks formed inside the cement sheath as well as debonding towards casing and formation.
This paper describes this laboratory set-up in detail. Furthermore, some preliminary experimental results are also included that demonstrates the applicability and functionality of the new set-up.
The SWARMs Approach to Integration of Underwater and Overwater Communication Sub-Networks and Integration of Heterogeneous Underwater Communication Systems
Authors: Pacini Francesco , Paoli Giacomo , Cayón Iván , Rivera Tamara , Sarmiento Beatriz , Kebkal Konstantin , Kebkal Oleksiy , Kebkal Veronika , Geelhoed Joost , Schipperijn Bart , Dol Henry , Skogseth Torstein 
Published: September 2018

The management of a heterogeneous mix of underwater vehicles needs a robust and reliable communication network, able to connect the remote command and control station (typically ashore or on board of a support ship) with nodes and vehicles in the deep sea. On the basis of this scenario, the infrastructure shall satisfy requirements such as: medium to extremely long distances between the control room and the area of operation; management of a variable number and type of nodes and vehicles (mobile, fixed, underwater, surfaced); a guaranteed bandwidth to send commands and receive platform status and tasks execution information with minimum latency; a high bitrate to transfer sensor data, pictures and videos in “near real time”; etc.
Compared to the available solutions used nowadays for radio communication systems, the underwater environment imposes several constraints on the maximum achievable bandwidth and distance, drastically reducing data transfer rates. This means that the full communication network is a trade-off between different requirements and performances. The SWARMs project approach to this problem is to select, combine and integrate different and heterogeneous communication technologies, components and solutions, in order to obtain the best performances for the management and control of underwater vehicles during the execution of different missions and tasks.
The network is mainly based on commercial components, but specific adaptations were made in order to fulfil the requirements of ad hoc underwater and overwater sub networks in maritime specific scenarios. Several experiments and sea trials have allowed the verification of the performance of the full network and the optimization of its configuration according to the mission needs.