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1
Vasilyev, Leonid, Konstantinos Christakos e Brian Hannafious. "Treating Wind Measurements Influenced by Offshore Structures with CFD Methods". Energy Procedia 80 (2015): 223–28. http://dx.doi.org/10.1016/j.egypro.2015.11.425.
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Peric, Milovan, e Volker Bertram. "Trends in Industry Applications of Computational Fluid Dynamics for Maritime Flows". Journal of Ship Production and Design 27, n. 04 (1 novembre 2011): 194–201. http://dx.doi.org/10.5957/jspd.2011.27.4.194.
Testo completoAbstract (sommario):
This paper surveys developments in Computational Fluid Dynamics (CFD) applications for maritime structures (ships, propellers, and offshore structures) over the past decade. Progress is significant in integrating the process chain, particularly more automated model generation. Increased hardware power and progress in various aspects of the flow solvers allow more sophisticated applications and wider scope of applications. Selected examples taken from industry and research applications show the increasing importance of CFD in earlier design stages.
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A. Rahman, Mohd Asamudin, Muhammad Nadzrin Nazri, Ahmad Fitriadhy, Mohammad Fadhli Ahmad, Erwan Hafizi Kasiman, Mohd Azlan Musa, Fatin Alias e Mohd Hairil Mohd. "A Fundamental CFD Investigation of Offshore Structures for Artificial Coral Reef Development". CFD Letters 12, n. 7 (30 luglio 2020): 110–25. http://dx.doi.org/10.37934/cfdl.12.7.110125.
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Van den Abeele, F., e J. Vande Voorde. "Stability of offshore structures in shallow water depth". International Journal Sustainable Construction & Design 2, n. 2 (6 novembre 2011): 320–33. http://dx.doi.org/10.21825/scad.v2i2.20529.
Testo completoAbstract (sommario):
The worldwide demand for energy, and in particular fossil fuels, keeps pushing the boundaries of offshoreengineering. Oil and gas majors are conducting their exploration and production activities in remotelocations and water depths exceeding 3000 meters. Such challenging conditions call for enhancedengineering techniques to cope with the risks of collapse, fatigue and pressure containment.On the other hand, offshore structures in shallow water depth (up to 100 meter) require a different anddedicated approach. Such structures are less prone to unstable collapse, but are often subjected to higherflow velocities, induced by both tides and waves. In this paper, numerical tools and utilities to study thestability of offshore structures in shallow water depth are reviewed, and three case studies are provided.First, the Coupled Eulerian Lagrangian (CEL) approach is demonstrated to combine the effects of fluid flowon the structural response of offshore structures. This approach is used to predict fluid flow aroundsubmersible platforms and jack-up rigs.Then, a Computational Fluid Dynamics (CFD) analysis is performed to calculate the turbulent Von Karmanstreet in the wake of subsea structures. At higher Reynolds numbers, this turbulent flow can give rise tovortex shedding and hence cyclic loading. Fluid structure interaction is applied to investigate the dynamicsof submarine risers, and evaluate the susceptibility of vortex induced vibrations.As a third case study, a hydrodynamic analysis is conducted to assess the combined effects of steadycurrent and oscillatory wave-induced flow on submerged structures. At the end of this paper, such ananalysis is performed to calculate drag, lift and inertia forces on partially buried subsea pipelines.
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Decorte, Griet, Alessandro Toffoli, Geert Lombaert e Jaak Monbaliu. "On the Use of a Domain Decomposition Strategy in Obtaining Response Statistics in Non-Gaussian Seas". Fluids 6, n. 1 (7 gennaio 2021): 28. http://dx.doi.org/10.3390/fluids6010028.
Testo completoAbstract (sommario):
During recent years, thorough experimental and numerical investigations have led to an improved understanding of dynamic phenomena affecting the fatigue life and survivability of offshore structures, e.g., ringing and springing and extreme wave impacts. However, most of these efforts have focused on modeling either selected extreme events or sequences of highly nonlinear waves impacting offshore structures, possibly overestimating the actual load to be experienced by the structure. Overall, not much has been done regarding short-term statistics. Although clear non-Gaussian statistics and therefore higher probabilities of extreme waves have been observed in random seas due to wave–wave interaction phenomena, which can impact short-term statistics for the structural load, they have not been studied extensively regarding the assessment of the dynamic behavior of offshore structures. Computational fluid dynamics (CFD) models have shown their viability for studying wave–structure interaction phenomena. Despite the continuously increasing computational resources, these models remain too computationally demanding for applications to the large spatial domains and long periods of time necessary for studying short-term statistics of non-Gaussian seas. Higher-order spectral (HOS) models, on the other hand, have been proven to be efficient and adequate in studying non-Gaussian seas. We therefore propose a one-way domain decomposition strategy, which takes full advantage of the recent advances in CFD and of the computational benefits of HOS. When applying this domain decomposition strategy, it appeared to be possible to deduce response statistics regarding the impact of nonlinear wave–wave interactions.
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Decorte, Griet, Alessandro Toffoli, Geert Lombaert e Jaak Monbaliu. "On the Use of a Domain Decomposition Strategy in Obtaining Response Statistics in Non-Gaussian Seas". Fluids 6, n. 1 (7 gennaio 2021): 28. http://dx.doi.org/10.3390/fluids6010028.
Testo completoAbstract (sommario):
During recent years, thorough experimental and numerical investigations have led to an improved understanding of dynamic phenomena affecting the fatigue life and survivability of offshore structures, e.g., ringing and springing and extreme wave impacts. However, most of these efforts have focused on modeling either selected extreme events or sequences of highly nonlinear waves impacting offshore structures, possibly overestimating the actual load to be experienced by the structure. Overall, not much has been done regarding short-term statistics. Although clear non-Gaussian statistics and therefore higher probabilities of extreme waves have been observed in random seas due to wave–wave interaction phenomena, which can impact short-term statistics for the structural load, they have not been studied extensively regarding the assessment of the dynamic behavior of offshore structures. Computational fluid dynamics (CFD) models have shown their viability for studying wave–structure interaction phenomena. Despite the continuously increasing computational resources, these models remain too computationally demanding for applications to the large spatial domains and long periods of time necessary for studying short-term statistics of non-Gaussian seas. Higher-order spectral (HOS) models, on the other hand, have been proven to be efficient and adequate in studying non-Gaussian seas. We therefore propose a one-way domain decomposition strategy, which takes full advantage of the recent advances in CFD and of the computational benefits of HOS. When applying this domain decomposition strategy, it appeared to be possible to deduce response statistics regarding the impact of nonlinear wave–wave interactions.
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Wu, Yanling. "Numerical tools to predict the environmental loads for offshore structures under extreme weather conditions". Modern Physics Letters B 32, n. 12n13 (10 maggio 2018): 1840039. http://dx.doi.org/10.1142/s0217984918400390.
Testo completoAbstract (sommario):
In this paper, the extreme waves were generated using the open source computational fluid dynamic (CFD) tools — OpenFOAM and Waves2FOAM — using linear and nonlinear NewWave input. They were used to conduct the numerical simulation of the wave impact process. Numerical tools based on first-order (with and without stretching) and second-order NewWave are investigated. The simulation to predict force loading for the offshore platform under the extreme weather condition is implemented and compared.
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Dymarski, Paweł, Ewelina Ciba e Tomasz Marcinkowski. "Effective Method for Determining Environmental Loads on Supporting Structures for Offshore Wind Turbines". Polish Maritime Research 23, n. 1 (1 gennaio 2016): 52–60. http://dx.doi.org/10.1515/pomr-2016-0008.
Testo completoAbstract (sommario):
Abstract This paper presents a description of an effective method for determining loads due to waves and current acting on the supporting structures of the offshore wind turbines. This method is dedicated to the structures consisting of the cylindrical or conical elements as well as (truncates) pyramids of polygon with a large number of sides (8 or more). The presented computational method is based on the Morison equation, which was originally developed only for cylindrically shaped structures. The new algorithm shown here uses the coefficients of inertia and drag forces that were calculated for non-cylindrical shapes. The analysed structure consists of segments which are truncated pyramids on the basis of a hex decagon. The inertia coefficients, CM, and drag coefficients, CD, were determined using RANSE-CFD calculations. The CFD simulations were performed for a specific range of variation of the period, and for a certain range of amplitudes of the velocity. In addition, the analysis of influence of the surface roughness on the inertia and drag coefficients was performed. In the next step, the computations of sea wave, current and wind load on supporting structure for the fifty-year storm were carried out. The simulations were performed in the time domain and as a result the function of forces distribution along the construction elements was obtained. The most unfavourable distribution of forces will be used, to analyse the strength of the structure, as the design load.
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Dervilis, Nikolaos, A. C. W. Creech, A. E. Maguire, Ifigeneia Antoniadou, R. J. Barthorpe e Keith Worden. "An SHM View of a CFD Model of Lillgrund Wind Farm". Applied Mechanics and Materials 564 (giugno 2014): 164–69. http://dx.doi.org/10.4028/www.scientific.net/amm.564.164.
Testo completoAbstract (sommario):
Reliability of offshore wind farms is one of the key areas for the successful implementation of these renewable power plants in the energy arena. Failure of the wind turbine (WT) in general could cause massive financial losses but especially for structures that are operating in offshore sites. Structural Health Monitoring (SHM) of WTs is essential in order to ensure not only structural safety but also avoidance of overdesign of components that could lead to economic and structural inefficiency. A preliminary analysis of a machine learning approach in the context of WT SHM is presented here; it is based on results from a Computational Fluid Dynamics (CFD) model of Lillgrund Wind farm. The analysis is based on neural network regression and is used to predict the measurement of each WT from the measurements of other WTs in the farm. Regression model error is used as an index of abnormal response.
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Rahman, Shaikh Atikur, Zubair Imam Syed, John V. Kurian e M. S. Liew. "Structural Response of Offshore Blast Walls under Accidental Explosion". Advanced Materials Research 1043 (ottobre 2014): 278–82. http://dx.doi.org/10.4028/www.scientific.net/amr.1043.278.
Testo completoAbstract (sommario):
Adequate blast resistant barriers are requisite to protect personnel and critical systems from the consequences of an accidental explosion and subsequent fire. Many of the blast walls currently installed in offshore structures were designed using simplified calculation approaches like Single Degree of Freedom models (SDOF) as recommended in many design guidelines. Over simplified and idealised explosion load used for response calculation and design of blast wall can lead to inadequate or overdesign of offshore blast walls. Due to lack of presence of a well-accepted design guidelines supported by extensive study, the protection provided by the conventional blast walls for offshore structures can be inadequate. In-depth understanding of structural response of blast walls under different blast loading can provide better design practice of blast walls for adequate protection. In this study, structural responses of conventional offshore blast walls were investigated. A computation fluid dynamics (CFD) approach was used to predict effect of different explosions on the barrier walls and non-linear finite elements analyses were performed to study the behaviour of the blast-loaded walls under different explosions. Effect of different parameters related to blast wall and accidental explosions were investigated to gain detail understanding of structural behaviour of typical steel blast wall.
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Jujuly, M. M., Mohammad Azizur Rahman, Aaron Maynard e Matthew Adey. "Hydrate-Induced Vibration in an Offshore Pipeline". SPE Journal 25, n. 02 (31 dicembre 2019): 732–43. http://dx.doi.org/10.2118/187378-pa.
Testo completoAbstract (sommario):
Summary Gas-hydrate plugging poses an operational challenge to offshore petroleum production and transportation. In this study, a computational-fluid-dynamics (CFD) model that uses ANSYS Fluent (ANSYS 2019) multiphase-flow-modeling techniques to simulate and analyze the effect of gas-hydrate flow in pipelines is proposed. For this purpose, the study attempted to integrate the ANSYS Fluent model with an existing commercial subsea-pipeline-visualization tool. To validate the simulation results, two case studies were conducted. The first study was about a pipeline whose dimensions are based on the specifications in existing literature (Balakin et al. 2010a). The second study was about a pipeline with more-complex geometry (M-shaped jumper with six elbows). The Eulerian/Eulerian method was used to model the multiphase hydrate flow. The population-balance method (PBM) was then used to model hydrate agglomeration and its breakup mechanism in the flow. A parametric study of the stresses in the pipelines resulting from flow-induced vibration (FIV) was conducted to identify the regions that underwent the maximum stresses and deformations under various flow conditions. The tool can be used in the petroleum industry to identify the operational hazards in offshore structures and to take necessary safety measures to avoid any potential catastrophic events.
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Lara, Javier L., Inigo J. Losada, Gabriel Barajas, Maria Maza e Benedetto Di Paolo. "RECENT ADVANCES IN 3D MODELLING OF WAVE-STRUCTURE INTERACTION WITH CFD MODELS". Coastal Engineering Proceedings, n. 36 (30 dicembre 2018): 91. http://dx.doi.org/10.9753/icce.v36.waves.91.
Testo completoAbstract (sommario):
Numerical modelling of the interaction of water waves with coastal structures has continuously been among the most relevant challenges in coastal engineering research and practice. During the last years, 3D modelling based on RANS-type equations, has been the dominant methodology to address the mathematical modelling of wave and coastal structure interaction. However, the three-dimensionality of many flowstructure interactions processes demands overcoming existing modelling limitations. Under some circumstances relevant three-dimensional processes are still tackled using physical modelling. It has been shown that beyond numerical implementation of the well-known mathematical 3-D formulation of the Navier-Stokes equations, the application of 3-D codes to standard coastal engineering problems demands some additional steps to be taken. These steps could be classified into three main groups relevant to: a) the modelling of the physical processes; b) the use of the tool and c) the applicability of the codes. This work presents an analysis of the use of three-dimensional flow models to analyze wave interaction with coastal structures focusing on recent developments overcoming existing limitations. Last modelling advances, including the implementation of new physics and pre-and postprocessing tools will be shown with the aim of extending the use of three-dimensional modelling of wavestructure interaction in both coastal and offshore fields.
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Zhou, Xiao, Liu, Incecik, Peyrard, Li e Pan. "Numerical Modelling of Dynamic Responses of a Floating Offshore Wind Turbine Subject to Focused Waves". Energies 12, n. 18 (9 settembre 2019): 3482. http://dx.doi.org/10.3390/en12183482.
Testo completoAbstract (sommario):
In this paper, we present numerical modelling for the investigation of dynamic responses of a floating offshore wind turbine subject to focused waves. The modelling was carried out using a Computational Fluid Dynamics (CFD) tool. We started with the generation of a focused wave in a numerical wave tank based on a first-order irregular wave theory, then validated the developed numerical method for wave-structure interaction via a study of floating production storage and offloading (FPSO) to focused wave. Subsequently, we investigated the wave-/wind-structure interaction of a fixed semi-submersible platform, a floating semi-submersible platform and a parked National Renewable Energy Laboratory (NREL) 5 MW floating offshore wind turbine. To understand the nonlinear effect, which usually occurs under severe sea states, we carried out a systematic study of the motion responses, hydrodynamic and mooring tension loads of floating offshore wind turbine (FOWT) over a range of wave steepness, and compared the results obtained from two potential flow theory tools with each other, i.e., Électricité de France (EDF) in-house code and NREL Fatigue, Aerodynamics, Structures, and Turbulence (FAST). We found that the nonlinearity of the hydrodynamic loading and motion responses increase with wave steepness, revealed by higher-order frequency response, leading to the appearance of discrepancies among different tools.
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Stahlmann, Arne, e Torsten Schlurmann. "INVESTIGATIONS ON SCOUR DEVELOPMENT AT TRIPOD FOUNDATIONS FOR OFFSHORE WIND TURBINES: MODELING AND APPLICATION". Coastal Engineering Proceedings 1, n. 33 (25 ottobre 2012): 90. http://dx.doi.org/10.9753/icce.v33.sediment.90.
Testo completoAbstract (sommario):
Regarding offshore constructions, there is still a lack in knowledge of scour progression for complex structures like foundations for offshore wind energy converters at present, which is however necessary for its dimensioning. As an example of such complex structure types, tripod foundations are constructed in German offshore wind farms at present. In order to describe physical processes and influencing factors on scour progression from a scientific point of view, comprehensive investigations on the scouring phenomena for tripod foundations have been carried out and will be partly presented here. The overall investigation method consists of a combination of 1:40 small and 1:12 large scale physical model tests in wave flumes, numerical simulations using CFD methods and in-situ measured scour data. For the numerical modeling part, a sediment transport model formulation has been implemented into OpenFOAM software code. The results show a general variability of scour depending on the load boundary conditions and structural parameters. Scours occur both at the foundation piles and directly under the structure, which in this form could not be predicted using standard approaches, but which has to be taken into account when regarding the soil mechanical stability and the final dimensioning of the foundations.
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Wang, Weizhi, Arun Kamath e Hans Bihs. "IRREGULAR WAVE MODELLING WITH CFD IN SULAFJORD FOR THE E39 PROJECT". Coastal Engineering Proceedings, n. 36 (30 dicembre 2018): 45. http://dx.doi.org/10.9753/icce.v36.waves.45.
Testo completoAbstract (sommario):
The E39 project aims at building a continuous ferry-free coastal highway along the west coast of Norway. Sulafjord is one of the fjords where ferries are to be replaced with floating bridges or floating tunnels. The floating structures demand accurate and realistic numerical simulations of the wave propagation and transformation in the fjords. The Norwegian coastline is characterized by dramatic water depth changes and deep water conditions. The coastal water also contains both swells and local wind-generated waves. These conditions, along with series of islands outside the fjords and very irregular coastline, make wave modeling more challenging for this region. Thus, the application of CFD models which provide high-resolution and phase-resolved solutions for complicated wave freesurface is explored. First, the spectral wave model SWAN is used to estimate the wave properties at the inlet of the Sulafjord from offshore wave data. Using the estimated wave data at the inlet as input, a large-scale 3D regular wave CFD simulation is performed using the open-source model REEF3D. Then unidirectional and multi-directional irregular wave CFD simulations are performed to represent a more realistic sea state, using a frequency spectra and a directional spreading function. The statistical properties of the simulated irregular ocean waves at three locations inside the fjord are compared among the CFD simulations and with the spectral wave model. The differences in the simulation results are discussed and studied.
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Teigen, P., V. P. Przulj e B. A. Younis. "A CFD Investigation Into the Effects of Current Incidence on the Hydrodynamic Loading on a Deepwater TLP". Journal of Offshore Mechanics and Arctic Engineering 121, n. 2 (1 maggio 1999): 109–15. http://dx.doi.org/10.1115/1.2830074.
Testo completoAbstract (sommario):
The use in the offshore engineering industry of computational fluid dynamics (CFD) to estimate the hydrodynamic forces due to steady, turbulent currents on offshore structures has so far been rather limited. This is largely due to the uncertainties inherent in obtaining accurate solutions to the governing Navier-Stokes equations, particularly for complex geometries and at high Reynolds numbers. In this study, we assess the contributions to such uncertainties arising from a number of factors. Those include the number of nodes in the computational mesh used to overlay the flow domain, the choice of scheme used to discretize the governing equations, the choice of turbulence model used to close the time-averaged equations, and the assumptions made regarding the state of turbulence in the incident current. The influence of these factors is systematically assessed with respect to the flow around a full-scale mini-TLP. The paper also assesses the influence of the current incidence on the hydrodynamic loads on the same TLP. A previous study by the same authors has suggested the presence of substantial “shielding,” whereby the computed steady-state loading on the TLP was found to be significantly lower than the value recommended by the DNV design code. Computations performed here with the direction of the incident current varied in the range 0–45 deg suggest that the extent of this shielding is significantly diminished at high angles of incidence.
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Cui, W.-C. "A feasible study of fatigue life prediction for marine structures based on crack propagation analysis". Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 217, n. 1 (1 marzo 2003): 11–23. http://dx.doi.org/10.1243/147509003321623112.
Testo completoAbstract (sommario):
Marine structures such as ships and offshore platforms are designed with damage tolerance. This requires accurate prediction of fatigue crack growth under service conditions. Current fatigue strength assessment methods for marine structures are largely based on the cumulative fatigue damage (CFD) theory using stress-endurance (S-N) curves. The effects of initial defects and the load sequence have been neglected. The extent of final fatigue failure in real structures is also not specified. These result in a large scatter of the predicted fatigue lives. In the fatigue community, more and more researchers have realized that fatigue crack propagation (FCP) theory could overcome these deficiencies and has the potential to explain various fatigue phenomena observed. In this paper, a feasible study of fatigue life prediction for marine structures based on FCP theory is carried out. The basic requirements and the general procedure for such an analysis are addressed. The feasibility of this procedure and the capabilities of FCP theory for fatigue life prediction are demonstrated using a simple example of a finite width plate with a centre crack subjected to remote uniform fatigue loading. The key problems to be solved for a practical implementation are also discussed.
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Cornett, Andrew. "EXTREME WAVE PRESSURES AND LOADS ON A PILE-SUPPORTED WHARF DECK - INFLUENCES OF AIR GAP AND WAVE DIRECTION". Coastal Engineering Proceedings, n. 36 (30 dicembre 2018): 5. http://dx.doi.org/10.9753/icce.v36.waves.5.
Testo completoAbstract (sommario):
Many deck-on-pile structures are located in shallow water depths at elevations low enough to be inundated by large waves during intense storms or tsunami. Many researchers have studied wave-in-deck loads over the past decade using a variety of theoretical, experimental, and numerical methods. Wave-in-deck loads on various pile supported coastal structures such as jetties, piers, wharves and bridges have been studied by Tirindelli et al. (2003), Cuomo et al. (2007, 2009), Murali et al. (2009), and Meng et al. (2010). All these authors analyzed data from scale model tests to investigate the pressures and loads on beam and deck elements subject to wave impact under various conditions. Wavein- deck loads on fixed offshore structures have been studied by Murray et al. (1997), Finnigan et al. (1997), Bea et al. (1999, 2001), Baarholm et al. (2004, 2009), and Raaij et al. (2007). These authors have studied both simplified and realistic deck structures using a mixture of theoretical analysis and model tests. Other researchers, including Kendon et al. (2010), Schellin et al. (2009), Lande et al. (2011) and Wemmenhove et al. (2011) have demonstrated that various CFD methods can be used to simulate the interaction of extreme waves with both simple and more realistic deck structures, and predict wave-in-deck pressures and loads.
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VIDYA, C., J. SHEEJA e M. SEKAR. "TOWARDS REDUCING COMPUTATIONAL EFFORT IN VORTEX INDUCED VIBRATION PREDICTIONS OF A CYLINDRICAL RISER." Periódico Tchê Química 16, n. 33 (20 marzo 2019): 841–53. http://dx.doi.org/10.52571/ptq.v16.n33.2019.856_periodico33_pgs_841_853.pdf.
Testo completoAbstract (sommario):
Vibrations induced by flow, generally referred to as vortex induced vibrations, are of great importance in the design of marine risers. These flexible cylindrical risers undergo vibrations of very high amplitude when the vortex shedding frequency matches the natural frequency of the riser. Such vibrations are capable of putting the safety of crew working on offshore platforms in question. Hence the prediction of response of such structures is considered very important. Although a lot of numerical work has been done in this field treating the problem as a two-way fluid structure interaction, the fact that these works demand very high computational efforts has not made it pertinent where high end computing resources are not readily available. A quick prediction of the structural response of such slender structures needs to be handy to the engineers at times of need. This paper addresses a solution technique for such a problem through an economical method for quick and reliable prediction of riser response under vortex induced vibration utilizing minimum computational effort for moderate Reynolds number (Re = 3 x 105). Two dimensional flow simulations are carried out using RANSE based CFD followed by the uniform mapping of hydrodynamic forces on to the three dimensional riser. The grid used for the numerical simulation has been well validated against wind-tunnel experimental results for Re= 5.3 x 104. Hydrodynamic forces corresponding to the first three harmonics of natural frequency of the riser have been used as input in the structural solver to analyse the response using finite element method. Trajectories of the cylinder in the first three modes of vibration have been obtained, a typical eight figure pattern which is characteristic for lock-in vibration. It is found that the method is quite effective in the quick computation of flow induced vibration problems for low and moderate Reynolds numbers.
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Shang, Zhaohui, Huibin Yan, Weidong Ruan e Yong Bai. "A Study on a Quantitative Analysis Method for Fire and Explosion Risk Assessment of Offshore Platforms". Advances in Civil Engineering 2020 (9 ottobre 2020): 1–20. http://dx.doi.org/10.1155/2020/3098719.
Testo completoAbstract (sommario):
Proper design of the explosion loads is of vital importance in the risk assessment of explosions for offshore oil and gas installations. A quantitative assessment method for gas explosion loads in process modules of offshore platform is proposed in this paper. The proposed approach achieves the following three objectives: (a) defining a suitable number of leak scenarios quantitatively based on the Latin Hypercube Sampling (LHS) technique and statistical analysis; (b) defining the explosion scenarios according to the computational fluid dynamics (CFD) dispersion analysis results in the sampled leak scenarios; (c) designing the explosion loads on interested areas according to the CFD analysis results in different explosion scenarios and exceedance probability methods. The proposed method was applied to a process module of an example offshore platform. The pressure loads on interested areas of the example platform are very close to that suggested in Det Norske Veritas (DNV) codes. The method developed in this paper can benefit the engineers on better assessment of gas explosion risk in process modules for offshore installations.
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Dharmavasan, S., e W. D. Dover. "Nondestructive Evaluation of Offshore Structures Using Fracture Mechanics". Applied Mechanics Reviews 41, n. 2 (1 febbraio 1988): 36–49. http://dx.doi.org/10.1115/1.3151880.
Testo completoAbstract (sommario):
Developments in fast modelling of processes, materials response and methodology in combination with appropriate knowledge based systems opens up the possibility of linking CAD/CAM with Computer Aided Serviceability (CAS) for use in a few industries. This paper reviews the tools and techniques which are available and being developed to implement this philosophy in non-destructive evaluation of offshore structures using fracture mechanics.
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Seo, Junwon, William Schaffer, Monique Head, Mehdi Shokouhian e Eunsoo Choi. "Integrated FEM and CFD Simulation for Offshore Wind Turbine Structural Response". International Journal of Steel Structures 19, n. 4 (29 gennaio 2019): 1112–24. http://dx.doi.org/10.1007/s13296-018-0191-y.
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Ahmed, Mushtaq, Zafarullah Nizamani, Akihiko Nakayama e Montasir Osman. "Some Recent Fluid-Structure Interaction Approaches for the Wave Current Behaviour With Offshore Structures". CFD Letters 12, n. 9 (30 settembre 2020): 15–26. http://dx.doi.org/10.37934/cfdl.12.9.1526.
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Elhanafi, Ahmed, Gregor Macfarlane e Dezhi Ning. "Hydrodynamic performance of single–chamber and dual–chamber offshore–stationary Oscillating Water Column devices using CFD". Applied Energy 228 (ottobre 2018): 82–96. http://dx.doi.org/10.1016/j.apenergy.2018.06.069.
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Li, Ru-Yu, Jin-Jian Chen e Chen-Cong Liao. "Numerical Study on Interaction between Submarine Landslides and a Monopile Using CFD Techniques". Journal of Marine Science and Engineering 9, n. 7 (2 luglio 2021): 736. http://dx.doi.org/10.3390/jmse9070736.
Testo completoAbstract (sommario):
Offshore installations with pile foundations in shallow water are vulnerable to submarine landslides, which cause serious damage to engineering facilities, loss of life, and loss of money. Due to a shortage of real observation data and the difficulty of reproduction, we lack insight into the interaction behavior between submarine landslides and monopiles. This study capitalized on ANSYS Fluent 20.0 to develop a three-dimensional biphasic (water and slurry) numerical model. This CFD model was used to analyze the interaction between a monopile and submarine landslides at different flow heights. The velocities of submarine landslides were from low to high values. Two modes of interactional forces acting on the monopile are proposed, which are (i) interaction force with peak value and (ii) interaction force without peak value. The influence of flow height and velocity on interaction forces was investigated. Results show that the effect of the flow heights on the interaction force is significant at low velocity stage, while the peak force representing a hazard level of the pile was non-negligible under high flow velocity and low flow height conditions, which should be considered in a future study. The related mechanisms are revealed with a hybrid model considering different components of the force.
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Goldan, Michael, e Robert J. G. A. Kroon. "As-Built Product Modeling and Reverse Engineering in Shipbuilding Through Combined Digital Photogrammetry and CAD/CAM Technology". Journal of Ship Production 19, n. 02 (1 maggio 2003): 98–104. http://dx.doi.org/10.5957/jsp.2003.19.2.98.
Testo completoAbstract (sommario):
Ship repair, as a technological "lesser brother" of shipbuilding, still contains major elements of manual labor. In the past years, ship repair and the conversion of ships and offshore structures came to rely increasingly on modern computer-aided design and manufacturing (CAD and CAM) information systems for speedy generation of the required engineering information. An often-encountered problem is the lack of product information in electronic form or in any other form. Such information is needed for engineering of new parts for damaged or converted ships and platforms. In such cases one needs to build the virtual product model from the existing as-built object up to an engineering-detail level; hence, the terms "as-built modeling" and "reverse engineering." The paper presents the results of a multiyear project with the code name AMORES, which focuses on improving lead time and economic efficiency in ship and offshore platform repair and conversion in the Netherlands. Existing and newly developed photogrammetric measuring techniques were used to generate as-built models of double curved three-dimensional surfaces of ships and platforms. These were fed into standard CAD/CAM systems to engineer and manufacture new ship hull or platform parts to replace damaged areas. The main advantages of the new method are savings in lead time (measurements, engineering) and the replacing of costly manual labor by modern digital photogrammetry. The paper will focus on the new developments, the experienced difficulties, and the advantages of this new technique in ship repair.
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Liu, Yichao, Daoyi Chen e Sunwei Li. "The artificial generation of the equilibrium marine atmospheric boundary layer for the CFD simulation of offshore wind turbines". Journal of Wind Engineering and Industrial Aerodynamics 183 (dicembre 2018): 44–54. http://dx.doi.org/10.1016/j.jweia.2018.10.008.
Testo completo
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Han, Young-Soo, Jaejoon Lee, Jungmin Lee, Wonhyuk Lee e Kyungho Lee. "3D CAD data extraction and conversion for application of augmented/virtual reality to the construction of ships and offshore structures". International Journal of Computer Integrated Manufacturing 32, n. 7 (11 aprile 2019): 658–68. http://dx.doi.org/10.1080/0951192x.2019.1599440.
Testo completo
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Buschinelli, P., J. D. Salazar, D. Regner, D. Oliveira, M. Machado, G. Marcellino, D. C. Sales et al. "TARGETLESS PHOTOGRAMMETRY NETWORK SIMULATION FOR INSPECTION PLANNING IN OIL AND GAS INDUSTRY". ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences V-1-2020 (3 agosto 2020): 285–91. http://dx.doi.org/10.5194/isprs-annals-v-1-2020-285-2020.
Testo completoAbstract (sommario):
Abstract. The oil and gas offshore industry demands regular inspections of components and structures that are subjected to extreme operational and environmental conditions. In this context, risers are pipelines that transport mainly oil, gas, water, and cables between submarine structures and the surface offshore platform, in the portion not touching the ocean floor. The emerged part of these risers is typically inspected by industrial climbing, which is a very time-consuming activity, has high operational costs, is dangerous and has a strong dependence on inspector skills. Remotely Piloted Aircraft Systems (RPAS) have been recently used for visual inspection of risers, however, no quantitative or geometrical evaluation has been conducted using this kind of image acquisition yet. An image-based measurement technique, such as close-range photogrammetry, can provide a 3D reconstruction using images, but a series of requisites is mandatory to achieve good results as image acquisition sequence, overlap, camera positioning network, spatial resolution and object texture in non-prepared and targetless scenes. The analysis of different image acquisition strategies using a real RPAS is too difficult because it demands a lot of time, good weather, daylight, and a scene similar to where risers are installed. An alternative is to use simulation. In this paper a ROS/Gazebo simulation is described and used to create a realistic textured 3D virtual environment of the platform, risers and RPA, providing a fast and low-cost solution to simulate different RPA trajectories for photogrammetry image acquisition in targetless scenes. These trajectories are evaluated by comparing the measured risers through photogrammetry to its CAD/simulated model. Since the scene is not prepared, the RPA position/orientation or a stereo vision setup can be used to set scale to the measurement result. The best trajectory found during simulations was also evaluated in a real experiment.
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Sacchi, Marco, Giuseppe De Natale, Volkhard Spiess, Lena Steinmann, Valerio Acocella, Marta Corradino, Shanaka de Silva et al. "A roadmap for amphibious drilling at the Campi Flegrei caldera: insights from a MagellanPlus workshop". Scientific Drilling 26 (2 dicembre 2019): 29–46. http://dx.doi.org/10.5194/sd-26-29-2019.
Testo completoAbstract (sommario):
Abstract. Large calderas are among the Earth's major volcanic features. They are associated with large magma reservoirs and elevated geothermal gradients. Caldera-forming eruptions result from the withdrawal and collapse of the magma chambers and produce large-volume pyroclastic deposits and later-stage deformation related to post-caldera resurgence and volcanism. Unrest episodes are not always followed by an eruption; however, every eruption is preceded by unrest. The Campi Flegrei caldera (CFc), located along the eastern Tyrrhenian coastline in southern Italy, is close to the densely populated area of Naples. It is one of the most dangerous volcanoes on Earth and represents a key example of an active, resurgent caldera. It has been traditionally interpreted as a nested caldera formed by collapses during the 100–200 km3 Campanian Ignimbrite (CI) eruption at ∼39 ka and the 40 km3 eruption of the Neapolitan Yellow Tuff (NYT) at ∼15 ka. Recent studies have suggested that the CI may instead have been fed by a fissure eruption from the Campanian Plain, north of Campi Flegrei. A MagellanPlus workshop was held in Naples, Italy, on 25–28 February 2017 to explore the potential of the CFc as target for an amphibious drilling project within the International Ocean Discovery Program (IODP) and the International Continental Drilling Program (ICDP). It was agreed that Campi Flegrei is an ideal site to investigate the mechanisms of caldera formation and associated post-caldera dynamics and to analyze the still poorly understood interplay between hydrothermal and magmatic processes. A coordinated onshore–offshore drilling strategy has been developed to reconstruct the structure and evolution of Campi Flegrei and to investigate volcanic precursors by examining (a) the succession of volcanic and hydrothermal products and related processes, (b) the inner structure of the caldera resurgence, (c) the physical, chemical, and biological characteristics of the hydrothermal system and offshore sediments, and (d) the geological expression of the phreatic and hydromagmatic eruptions, hydrothermal degassing, sedimentary structures, and other records of these phenomena. The deployment of a multiparametric in situ monitoring system at depth will enable near-real-time tracking of changes in the magma reservoir and hydrothermal system.
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Martin, Tobias, e Hans Bihs. "A CFD Approach for Modelling the Fluid-Structure Interaction of Offshore Aquaculture Cages and Waves". Journal of Offshore Mechanics and Arctic Engineering, 14 settembre 2021, 1–10. http://dx.doi.org/10.1115/1.4052421.
Testo completoAbstract (sommario):
Abstract Open ocean aquaculture cages became recently a promising alternative to traditional fish cage designs. The offshore environment implies larger loads on the structures and higher risk of fish loss. Floating rigid aquaculture cages with stiff nets are considered as a possible solution to cope with these new challenges. Their design process requires more advanced tools to account for the non-linear fluid-structure interaction. This paper presents a suitable numerical approach for analysing the interaction of offshore aquaculture cages and waves using Computational Fluid Dynamics. Here, a numerical wave tank accounts for the accurate propagation of the waves, and structural dynamics solutions are utilised for the cage system. Two-way coupling is enabled by accounting for the influence of the net on the fluid. The numerical model is validated against measurements for the loads on and the responses of a mobile floating fish farm in waves and current.
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Aggarwal, Ankit, Pietro D. Tomaselli, Erik Damgaard Christensen e Hans Bihs. "Computational Fluid Dynamics Investigations of Breaking Focused Wave-Induced Loads on a Monopile and the Effect of Breaker Location". Journal of Offshore Mechanics and Arctic Engineering 142, n. 2 (16 novembre 2019). http://dx.doi.org/10.1115/1.4045187.
Testo completoAbstract (sommario):
Abstract The design of new offshore structures requires the calculation of the wave-induced loads. In this regard, the computational fluid dynamics (CFD) methodology has shown to be a reliable tool, in the case of breaking waves especially. In this paper, two CFD models are tested in the reproduction of the experimental spilling waves impacting a circular cylinder for four different wave impact scenarios for focused waves. The numerical and experimental free surface elevations at different locations around the cylinder are also compared to verify the both numerical models. The numerical results from the models are shown together with the experimental measurements. Both CFD models are able to model the impact forces with a reasonable accuracy. When the cylinder is placed at a distance of 0.7 m from the wave breaking point, the value of the measured wave impact forces is highest due to the overturning wave crest and air entrainment. The wave-induced impact forces decrease, when the monopile is placed at distances further away from the breaking location.
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Chen Ong, Muk, Eirik Trygsland e Dag Myrhaug. "Numerical Study of Seabed Boundary Layer Flow Around Monopile and Gravity-Based Wind Turbine Foundations". Journal of Offshore Mechanics and Arctic Engineering 139, n. 4 (5 maggio 2017). http://dx.doi.org/10.1115/1.4036208.
Testo completoAbstract (sommario):
Computational fluid dynamics (CFD) has been used to study the seabed boundary layer flow around monopile and gravity-based offshore wind turbine foundations. The gravity-based foundation has a hexagonal bottom slab (bottom part). The objective of the present study is to investigate the formation of horseshoe vortex and flow structures around two different bottom-fixed offshore wind turbine foundations in order to provide an assessment of potential scour for engineering design. Three-dimensional CFD simulations have been performed using Spalart–Allmaras delayed detached eddy simulation (SADDES) at a Reynolds number 4 × 106 based on the freestream velocity and the diameter of the monopile foundation, D. A seabed boundary layer flow with a boundary layer thickness D is assumed for all the simulations. Vortical structures, time-averaged results of velocity distributions and bed shear stresses are computed. The numerical results are discussed by studying the difference in flows around the monopile and the gravity-based foundations. A distinct horseshoe vortex is found in front of the monopile foundation. Two small horseshoe vortices are found in front of the hexagonal gravity-based foundation, i.e., one is on the top of the bottom slab and one is near the seabed in front of the bottom slab. The horseshoe vortex size for the hexagonal gravity-based foundation is found to be smaller than that for the monopile foundation. The effects of different foundation geometries on destroying the formation of horseshoe vortices (which is the main cause of scour problems) are discussed.
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Nematbakhsh, Ali, Zhen Gao e Torgeir Moan. "Benchmarking of a Computational Fluid Dynamics-Based Numerical Wave Tank for Studying Wave Load Effects on Fixed and Floating Offshore Structures". Journal of Offshore Mechanics and Arctic Engineering 139, n. 3 (5 aprile 2017). http://dx.doi.org/10.1115/1.4035475.
Testo completoAbstract (sommario):
A computational fluid dynamics (CFD) based numerical wave tank (NWT) is developed and verified to study wave load effects on fixed and free floating offshore structures. The model is based on solving Navier–Stokes equations on a structured grid, level set method for tracking the free surface, and an immersed boundary method for studying wave–structure interaction. This paper deals with establishing and verifying a CFD-based NWT. Various concerns that arise during this establishment are discussed, namely effects of wave reflection which might affect the structure response, damping of waves in downstream, and three-dimensional (3D) effects of the waves. A method is described and verified to predict the time when incoming waves from wave generator are affected by reflecting waves from the structure which can help in better designing the dimensions of NWT. The model is then used to study sway, heave, and roll responses of a floating barge which is nonuniform in density and limited in sway direction by a spring and damper. Also, it is used to study wave loads on a fixed, large diameter, surface piercing circular cylinder. The numerical results are compared with the experimental and other numerical results, and in general very good agreement is observed in all range of studied wave frequencies. It is shown that for the studied fixed cylinder, the Morison equation leads to promising results for wavelength to diameter ratio larger than 2π (kD < 1), while for shorter wavelengths results in considerable over prediction of wave loads, due to simplification of wave diffraction effects.
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"Numerical Examination on the Effect of Internal Fluid Presssure on the Hydrodynamic Response of a Marine Riser". International Journal of Innovative Technology and Exploring Engineering 8, n. 11S (11 ottobre 2019): 1310–15. http://dx.doi.org/10.35940/ijitee.k1265.09811s19.
Testo completoAbstract (sommario):
Marine risers are long slender structures which links the floating vessel on the sea surface and its manifold on the sea bottom. It acts as a transportation means for the hydrocarbon resources underneath the sea bed. A riser mainly undergoes hydrodynamic loading which leads to Vortex induced vibrations (VIV) or Flow induced vibrations. These are motions induced on bodies interacting with an external fluid flow producing periodic irregularities on the flow which leads to fatigue damage of offshore oil exploration and production risers. Therefore, suppressing of VIV by providing helical strakes, fairings etc. is necessary in order to reduce the fatigue damage of risers due to hydrodynamic loading. The present paper deals with the numerical study on the response of a marine riserdue to the effect of internalfluid pressure. The initial work is carried out in ANSYS ICEM CFD software. The CFD solution after analysis is obtained from ANSYS FLUENT. The hydrodynamic effects like lift and drag forces along with motion responses is obtained.
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Gonçalves, Rodolfo Trentin, Shinichiro Hirabayashi, Guilherme Vaz e Hideyuki Suzuki. "Force Measurements of the Flow Around Arrays of Three and Four Columns With Different Geometry Sections, Spacing Ratios, and Incidence Angles". Journal of Offshore Mechanics and Arctic Engineering 142, n. 2 (16 novembre 2019). http://dx.doi.org/10.1115/1.4045212.
Testo completoAbstract (sommario):
Abstract An experimental campaign for the flow around a stationary array of three and four columns with low aspect ratio, H/L = 1.5, piercing the water free surface, was carried out in a towing tank. These numbers of columns correspond to typical multi-column offshore systems, such as semi-submersibles (SS), tension leg platforms (TLPs), and floating offshore wind turbines (FOWTs). Three parameters were investigated: the spacing ratio between column centers (from two up to four characteristic lengths), current incidence angles, and column section geometries (circular, square, and diamond). The Reynolds number of the experiments was 100,000. Forces were measured in each column using a three degrees-of-freedom load cell, and results of lift and drag forces were presented for each column separately and the whole system. The results of mean and standard deviation of forces were assessed using a statistical uncertainty analysis procedure for finite length measurements’ signals. This methodology not only assesses the quality of the experimental data but also facilitates validation of numerical tools. The objectives of the current work were therefore manifold: to better understand the influence of the relative position, shape, and incidence angle on multi-column offshore structures; to create a reliable database for computational fluid dynamics (CFD) validation; and to prepare the path to flow-induced motions (FIMs) experimental and numerical work of free-moving multi-column offshore systems.
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Bihs, Hans, Arun Kamath, Ankit Aggarwal e Csaba Pakozdi. "Efficient Wave Modeling Using Nonhydrostatic Pressure Distribution and Free Surface Tracking on Fixed Grids". Journal of Offshore Mechanics and Arctic Engineering 141, n. 4 (8 aprile 2019). http://dx.doi.org/10.1115/1.4043179.
Testo completoAbstract (sommario):
For the estimation of wave loads on offshore structures, relevant extreme wave events need to be identified. In order to achieve this, long-term wave simulations of relatively large scales need to be performed. Computational fluid dynamics (CFD) based numerical wave tanks with an interface capturing two-phase flow approach typically require too large computational resources. In this paper, a three-dimensional (3D) nonhydrostatic wave model is presented, which solves the Navier–Stokes equations and employs an interface tracking method based on the continuity of the horizontal velocities along the vertical water column. With this approach, relatively fewer cells are needed in the vicinity of the air–water interface compared to CFD-based numerical wave tanks. The numerical model solves the governing equations on a rectilinear grid, which allows for the employment of high-order finite differences. The capabilities of the new wave model are presented by comparing the wave propagation in the tank with the CFD approach in a two-dimensional (2D) simulation. Further, a 3D simulation is carried out to determine the wave forces on a vertical cylinder. The calculated wave forces using the new approach are compared to those obtained using the CFD approach and experimental data. It is seen that the new approach provides a similar accuracy to that from the CFD approach while providing a large reduction in the time taken for the simulation. The gain is calculated to be about 4.5 for the 2D simulation and about 7.1 for the 3D simulation.
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Ebrahimnejad, L., K. D. Janoyan, H. Yadollahi Farsani, D. T. Valentine e P. Marzocca. "Efficient Predictions of Unsteady Viscous Flows Around Bluff Bodies by Aerodynamic Reduced Order Models". Journal of Offshore Mechanics and Arctic Engineering 136, n. 1 (25 ottobre 2013). http://dx.doi.org/10.1115/1.4025544.
Testo completoAbstract (sommario):
This paper describes an efficient reduced order model (ROM) applied in the aerodynamic analysis of bluff bodies. The proposed method, which is based on eigensystem realization algorithm (ERA), uses the impulse response of the system obtained by computational fluid dynamics (CFD) analysis to construct a ROM that can accurately predict the response of the system to any arbitrary input. In order to study the performance of the proposed technique, three different geometries including elliptical and rectangular sections as well as the deck cross section of Great Belt Bridge (GBB) were considered. The aerodynamic coefficients of the impulse responses of the three sections are used to construct the corresponding ROM for each section. Then, the aerodynamic coefficients from an arbitrary sinusoidal input obtained by CFD are compared with the predicted one using the ROM. The results presented illustrate the ability of the proposed technique to predict responses of the systems to arbitrary sinusoidal and other generic inputs, with significant savings in terms of CPU time when compared with most CFD codes. The methodology described in this paper has wide application in many offshore engineering problems where flexible structures interact with unsteady fluid flow, and should be useful in preliminary design, in design optimization, and in control algorithm development.
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Bihs, Hans, Weizhi Wang, Csaba Pakozdi e Arun Kamath. "REEF3D::FNPF—A Flexible Fully Nonlinear Potential Flow Solver". Journal of Offshore Mechanics and Arctic Engineering 142, n. 4 (20 febbraio 2020). http://dx.doi.org/10.1115/1.4045915.
Testo completoAbstract (sommario):
Abstract In situations where the calculation of ocean wave propagation and impact on structures are required, fast numerical solvers are desired in order to find relevant wave events. Computational fluid dynamics (CFD)-based numerical wave tanks (NWTs) emphasize on the hydrodynamic details such as fluid–structure interaction, which make them less ideal for the event identification due to the large computational resources involved. Therefore, a computationally efficient numerical wave model is needed to identify the events both for offshore deep-water wave fields and coastal wave fields where the bathymetry and coastline variations have strong impact on wave propagation. In the current paper, a new numerical wave model is represented that solves the Laplace equation for the flow potential and the nonlinear kinematic and dynamics free surface boundary conditions. This approach requires reduced computational resources compared to CFD-based NWTs. The resulting fully nonlinear potential flow solver REEF3D::FNPF uses a σ-coordinate grid for the computations. This allows the grid to follow the irregular bottom variation with great flexibility. The free surface boundary conditions are discretized using fifth-order weighted essentially non-oscillatory (WENO) finite difference methods and the third-order total variation diminishing (TVD) Runge–Kutta scheme for time stepping. The Laplace equation for the potential is solved with Hypre’s stabilized bi-conjugated gradient solver preconditioned with geometric multi-grid. REEF3D::FNPF is fully parallelized following the domain decomposition strategy and the message passing interface (MPI) communication protocol. The numerical results agree well with the experimental measurements in all tested cases and the model proves to be efficient and accurate for both offshore and coastal conditions.
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Bihs, Hans, Mayilvahanan Alagan Chella, Arun Kamath e Øivind Asgeir Arntsen. "Numerical Investigation of Focused Waves and Their Interaction With a Vertical Cylinder Using REEF3D". Journal of Offshore Mechanics and Arctic Engineering 139, n. 4 (10 maggio 2017). http://dx.doi.org/10.1115/1.4036206.
Testo completoAbstract (sommario):
For the stability of offshore structures, such as offshore wind foundations, extreme wave conditions need to be taken into account. Waves from extreme events are critical from the design perspective. In a numerical wave tank, extreme waves can be modeled using focused waves. Here, linear waves are generated from a wave spectrum. The wave crests of the generated waves coincide at a preselected location and time. Focused wave generation is implemented in the numerical wave tank module of REEF3D, which has been extensively and successfully tested for various wave hydrodynamics and wave–structure interaction problems in particular and for free surface flows in general. The open-source computational fluid dynamics (CFD) code REEF3D solves the three-dimensional Navier–Stokes equations on a staggered Cartesian grid. Higher order numerical schemes are used for time and spatial discretization. For the interface capturing, the level set method is selected. In order to test the generated waves, the time series of the free surface elevation are compared with experimental benchmark cases. The numerically simulated free surface elevation shows good agreement with experimental data. In further computations, the impact of the focused waves on a vertical circular cylinder is investigated. A breaking focused wave is simulated and the associated kinematics is investigated. Free surface flow features during the interaction of nonbreaking focused waves with a cylinder and during the breaking process of a focused wave are also investigated along with the numerically captured free surface.
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Chella, Mayilvahanan Alagan, Hans Bihs, Dag Myrhaug e Øivind Asgeir Arntsen. "Numerical Modeling of Breaking Wave Kinematics and Wave Impact Pressures on a Vertical Slender Cylinder". Journal of Offshore Mechanics and Arctic Engineering 141, n. 5 (15 febbraio 2019). http://dx.doi.org/10.1115/1.4042265.
Testo completoAbstract (sommario):
Wave loads from breaking waves on offshore wind turbine (OWT) substructures in shallow waters still remain uncertain. The interaction of breaking waves with structures is characterized by complex free surface deformations, instantaneous impact of the water mass against the structure, and consequently large wave forces on the structures. The main objective of the paper is to investigate wave impact pressures and kinematics during the interaction of breaking waves with a vertical cylinder using the open-source computational fluid dynamics (CFD) model REEF3D. The model is based on the Reynolds-averaged Navier–Stokes (RANS) equations coupled with the level set method and k–ω turbulence model. Three wave impact conditions are considered in this study. The numerically simulated free surface deformations around the cylinder during the breaking wave interaction are also presented for different wave impact conditions. For three wave impact conditions, the wave impact pressure and the horizontal and vertical components of the particle velocity are computed in front of the cylinder and analyzed. The pressure and velocity profile at their maximum values are also examined and discussed. In addition, the total force is calculated for three breaking conditions and they are correlated with the pressure and kinematics during the interaction.
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Sasikumar, Athul, Arun Kamath, Onno Musch, Hans Bihs e Øivind A. Arntsen. "Numerical Modeling of Berm Breakwater Optimization With Varying Berm Geometry Using REEF3D". Journal of Offshore Mechanics and Arctic Engineering 141, n. 1 (13 agosto 2018). http://dx.doi.org/10.1115/1.4040508.
Testo completoAbstract (sommario):
Harbors are important infrastructures for an offshore production chain. These harbors are protected from the actions of sea by breakwaters to ensure safe loading, unloading of vessels and also to protect the infrastructure. In current literature, research regarding the design of these structures is majorly based on physical model tests. In this study a new tool, a three-dimensional (3D) numerical model is introduced. The open-source computational fluid dynamics (CFD) model REEF3D is used to study the design of berm breakwaters. The model uses the Volume-averaged Reynolds-averaged Navier-Stokes (VRANS) equations to solve the porous flows. At first, the VRANS approach in REEF3D is validated for flow through porous media. A dam break case is simulated and comparisons are made for the free surface both inside and outside the porous medium. The numerical model REEF3D is applied to show how to extend the database obtained with purely numerical results, simulating different structural alternatives for the berm in a berm breakwater. Different simulations are conducted with varying berm geometry. The influence of the berm geometry on the pore pressure and velocities are studied. The resulting optimal berm geometry is compared to the geometry according to empirical formulations.
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Koto, Jaswar, e Abdul Khair Junaidi. "Analysis of Vortex-Induced Vibration of Riser using Spalart-Almaras Model". Jurnal Teknologi 69, n. 7 (15 luglio 2014). http://dx.doi.org/10.11113/jt.v69.3260.
Testo completoAbstract (sommario):
Vortex-induced vibration is natural phenomena where an object is exposed to moving fluid caused vibration of the object. Vortex-induced vibration occurred due to vortex shedding behind the object. One of the offshore structures that experience this vortex-induced vibration is riser. The riser experience vortex-induced vibration due to vortex shedding caused by external load which is sea current. The effect of this vortex shedding to the riser is fatigue damage. Vortex-induced vibration of riser becomes the main concern in oil and gas industry since there will be a lots of money to be invested for the installation and maintenance of the riser. The previous studies of this vortex-induced vibration have been conducted by experimental method and Computational Fluid Dynamics (CFD) method in order to predict the vortex shedding behaviour behind the riser body for the determination of way to improve the riser design. This thesis represented the analysis of vortex induced vibration of rigid riser in two-dimensional. The analysis is conducted using Computational Fluid Dynamic (CFD) simulations at Reynolds number at 40, 200, 1000, and 1500. The simulations were performed using Spalart-Allmaras turbulent model to solve the transport equation of turbulent viscosity. The simulations results at Reynolds number 40 and 200 is compared with the other studies for the validation of the simulation, then further simulations were conducted at Reynolds number of 1000 and 1500. The coefficient of lift and drag were obtained from the simulations. The comparison of lift and drag coefficient between the simulation results in this study and experiment results from the other studies showed good agreement. Besides that, the in-line vibration and cross-flow vibration at different Reynolds number were also investigated. The drag coefficient obtained from the simulation results remain unchanged as the Reynolds number increased from 200 to 1500. The lift coefficient obtained from the simulations increased as the Reynolds number increased from 40 to 1500.
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Kamath, Arun, Hans Bihs e Øivind A. Arntsen. "Study of Water Impact and Entry of a Free Falling Wedge Using Computational Fluid Dynamics Simulations". Journal of Offshore Mechanics and Arctic Engineering 139, n. 3 (28 marzo 2017). http://dx.doi.org/10.1115/1.4035384.
Testo completoAbstract (sommario):
Many offshore constructions and operations involve water impact problems such as water slamming onto a structure or free fall of objects with subsequent water entry and emergence. Wave slamming on semisubmersibles, vertical members of jacket structures, crane operation of a diving bell, and dropping of free fall lifeboats are some notable examples. The slamming and water entry problems lead to large instantaneous impact pressures on the structure, accompanied with complex free surface deformations. These need to be studied in detail in order to obtain a better understanding of the fluid physics involved and develop safe and economical design. Numerical modeling of a free falling body into water involves several complex hydrodynamic features after its free fall such as water entry, submergence into water and resurfacing. The water entry and submergence lead to formation of water jets and air cavities in the water resulting in large impact forces on the object. In order to evaluate the forces and hydrodynamics involved, the numerical model should be able to account for the complex free surface features and the instantaneous pressure changes. The water entry of a free falling wedge into water is studied in this paper using the open source computational fluid dynamics (CFD) model REEF3D. The vertical velocity of the wedge during the process of free fall and water impact are calculated for different cases and the free surface deformations are captured in detail. Numerical results are compared with experimental data and a good agreement is seen.
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Fan, Ning, Wangcheng Zhang, Fauzan Sahdi e Tingkai Nian. "Evaluation of horizontal submarine slide impact force on pipeline via a modified hybrid geotechnical-fluid dynamics framework". Canadian Geotechnical Journal, 27 agosto 2021. http://dx.doi.org/10.1139/cgj-2021-0089.
Testo completoAbstract (sommario):
There are situations in offshore energy development where potential impact forces between submarine slides and pipelines need to be estimated. The horizontal slide-pipeline impact force, parallel to the main travel direction of the sliding mass and normal to the pipeline axis, is generally dominant compared to other force components, and hence of particular concern. In practice, pipelines may be suspended at varying distances above the seabed (gap) and existing methods do not consider how this will affect the horizontal slide-pipeline forces. This paper investigates the effects of pipeline-seabed gap and pipeline diameter on the horizontal slide-pipeline impact force via 181 computational fluid dynamics (CFD) simulations at Reynolds numbers of 0.36 - 287. Results show that variation in the pipeline-seabed gap and pipeline diameter alters the slide mass flow behavior as it flows past the pipeline and hence the impact force when the pipeline-seabed gap is below a critical value. A modified hybrid geotechnical-fluid dynamics framework for estimating the horizontal impact force is proposed by considering the effects of the pipeline-seabed gap and pipeline diameter, which is validated with existing experimental datasets.
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"Simulación numérica del sloshing". Revista ECIPeru, 10 gennaio 2019, 68–75. http://dx.doi.org/10.33017/reveciperu2011.0012/.
Testo completoAbstract (sommario):
Simulación numérica del sloshing Numerical simulation of sloshing Miguel A. Celis Carbajal, Juan B.V.Wanderley, Marcelo A.S. Neves Universidad Federal de Rio de Janeiro/COPPE, Rio de Janeiro, RJ, Brasil DOI: https://doi.org/10.33017/RevECIPeru2011.0012/ RESUMEN El sloshing es de gran importancia en la dinámica de los buques y plataformas offshore. Es uno de los factores que pueden causar cargas indeseables e incluso la zozobra de los cuerpos flotantes. Esto sucede cuando el buque está en condiciones no deseadas, tales como la inundación progresiva en condiciones de avería. El objetivo es representar numéricamente el efecto del sloshing, el modelo numérico está basado en el método de diferencias finitas, en el cual representaremos el fluido incompresible y sin efectos viscosos a través de la ecuación de Euler este se resuelven mediante el esquema upwind TVD (Disminución de la Variación Total), esta fue formulado por Roe (1984) [1] y Sweby (1984) [2]. El código computacional representa el efecto del sloshing en un compartimento cerrado en 2D y 3D. Para representar adecuadamente el compartimento se utiliza una malla computacional estructurada. Las condiciones iniciales son impuestas por un plano inclinado de la superficie libre. Otro intento de probar la versatilidad del código informático es mediante la simulación de la caída de una esfera de agua sobre la superficie libre del tanque con agua. Descriptores: CFD, Sloshing TVD. ABSTRACT In this paper, we study the effect of sloshing in a compartment of a naval artifact. The sloshing is of great importance in the dynamics of ships and offshore platforms, it is one of the factors that may cause the capsizing. This happens when the ship is under undesirable conditions, such as progressive flooding or fault conditions. The goal is to represent numerically the effect of sloshing. The numerical code is validated through comparisons with numerical and experimental data obtained in the literature. The numerical model is based on the finite difference method, where the Euler equations are solved using the upwind scheme and TVD (Total Variation Diminishing) Roe (1984) and Sweby (1984). The computer code for 2D represents the effect of sloshing in a closed vessel. To adequately represent the reservoir of the naval artifact, we used a structured computational mesh, where the fluid is forced to move by the excitation applied to the tank, this type of excitation is harmonic in sway. For the 3D computer code, a sloped free surface elevation is used as initial condition. Another attempt to realize the versatility of the computer code was the fall of a sphere of water on the free surface of the tank. Keywords: CFD, Sloshing TVD.
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Taylor, Rocky S., Ian J. Jordaan, Chuanke Li e Denise Sudom. "Local Design Pressures for Structures in Ice: Analysis of Full-Scale Data". Journal of Offshore Mechanics and Arctic Engineering 132, n. 3 (17 giugno 2010). http://dx.doi.org/10.1115/1.4000504.
Testo completoAbstract (sommario):
The design of structures for ice conditions requires knowledge of local ice pressures to allow for appropriate levels of structural strengthening. Full-scale field data are keys to enhancing our understanding and modeling of ice behavior. Data collected during icebreaker ramming events represent an important source of information for use in design load estimation, and the evaluation of design methodologies. This paper examines several ship-ice interaction data sets using the ‘event-maximum’ method of local pressure analysis developed by Jordaan and et al. (1993, “Probabilistic Analysis of Local Ice Pressures,” ASME J. Offshore Mech. Arct. Eng., 115, pp. 83–89). In this method, the local pressure is obtained from a normalized curve, which contains two parameters α and x0. The parameter α is a function of the area, well represented by the curve α=CaD, where a is the local area of interest, and C and D are constants. The parameter x0 is assumed a constant for a given design scenario. An alternative approach, the up-crossing rate method, is presented in a companion paper (2009, “Estimation of Local Ice Pressure Using Up-Crossing Rate,” Proceedings of the OMAE 2009, Honolulu, HI). Local pressure analysis results for data from the USCGS Polar Sea, CCGS Terry Fox, CCGS Louis St. Laurent, and Swedish Icebreaker Oden are presented. A discussion of panel exposure, event duration, and the effects of these factors on x0 is given. New design curves are included. For all data considered, the calculated values of α fall below the design curve. For the design, it is recommended that α is calculated using a C value based on the impact data collected under ice conditions similar to those for the design scenario; D may be treated as a constant having a value of −0.7. A design value of x0 may be determined based on the analysis of appropriate data sets. The treatment of exposure is described for data analysis and design. The effects of exposure must be removed during data analysis to provide a design curve based on single panel exposure. For the design, estimates from the design curves must be adjusted to properly reflect the design exposure.