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Littérature scientifique sur le sujet « Numerical grid generation (Numerical analysis) Tides »

Auteur : Grafiati

Publié le 4 juin 2021

Mis à jour le 1 février 2022

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Articles de revues sur le sujet "Numerical grid generation (Numerical analysis) Tides"

Vasilev, Eugene, Dmitry Lachinov, Anton Grishin et Vadim Turlapov. « Fast tetrahedral mesh generation and segmentation of an atlas-based heart model using a periodic uniform grid ». Russian Journal of Numerical Analysis and Mathematical Modelling 33, n^o 5 (27 novembre 2018) : 315–23. http://dx.doi.org/10.1515/rnam-2018-0026.

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Abstract A fast procedure for generation of regular tetrahedral finite element mesh for objects with complex shape cavities is proposed. The procedure like LBIE-Mesher can generate tetrahedral meshes for the volume interior to a polygonal surface, or for an interval volume between two surfaces having a complex shape and defined in STL-format. This procedure consists of several stages: generation of a regular tetrahedral mesh that fills the volume of the required object; generation of clipping for the uniform grid parts by a boundary surface; shifting vertices of the boundary layer to align onto the surface.We present a sequential and parallel implementation of the algorithm and compare their performance with existing generators of tetrahedral grids such as TetGen, NETGEN, and CGAL. The current version of the algorithm using the mobile GPU is about 5 times faster than NETGEN. The source code of the developed software is available on GitHub.

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Li, Guodong, Guoding Chen, Pengfeng Li et Haixiao Jing. « Efficient and Accurate 3-D Numerical Modelling of Landslide Tsunami ». Water 11, n^o 10 (29 septembre 2019) : 2033. http://dx.doi.org/10.3390/w11102033.

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High-speed and accurate simulations of landslide-generated tsunamis are of great importance for the understanding of generation and propagation of water waves and for prediction of these natural disasters. A three-dimensional numerical model, based on Reynolds-averaged Navier–Stokes equations, is developed to simulate the landslide-generated tsunami. Available experiment data is used to validate the numerical model and to investigate the scale effect of numerical model according to the Froude similarity criterion. Based on grid convergence index (GCI) analysis, fourteen cases are arranged to study the sensitivity of numerical results to mesh resolution. Results show that numerical results are more sensitive to mesh resolution in near field than that in the propagation field. Nonuniform meshes can be used to balance the computational efficiency and accuracy. A mesh generation strategy is proposed and validated, achieving an accurate prediction and nearly 22 times reduction of computational cost. Further, this strategy of mesh generation is applied to simulate the Laxiwa Reservoir landslide tsunami. The results of this study provide an important guide for the establishment of a numerical model of the real-world problem of landslide tsunami.

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Tokunaga, Shogo, et Taro Arikawa. « STUDY ON SCOURING IN PILE OF OFFSHORE WIND FARMING BY NUMERICAL ANALYSIS USING BUILDING-CUBE METHOD ». Coastal Engineering Proceedings, n^o 36v (28 décembre 2020) : 42. http://dx.doi.org/10.9753/icce.v36v.sediment.42.

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In recent years, offshore wind farming has spread all over the world, and there has been rapid growth of not only conventional onshore wind farming but also offshore wind farming in the sea. However, there are many problems to be solved in offshore wind farming. Among them, the scour of the ocean floor caused by wave and tide has a great influence on the support structure. The purpose of this study is to clarify the scour phenomenon from the flow field and vortex generation conditions by numerical simulation using Building Cube Method. We conducted the simulation of the experiment which handles scouring around the monopile performed by Chen et al. (2018). The Building Cube Method was developed by Nakahashi and Kim (2004). In this study, we used CADMAS-BCM (developed by Arikawa et al.) that 3-D Navier-Stokes simulation model using the Building Cube Method. In this model, the 3-D Building Cube Method was applied using multiple roots. Moreover, because the calculation area is divided according to simple rules, it has features such as good compatibility with parallel computers, and grid generation by a simple method is useful for calculating the flow around objects with complex shapes. Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/OlJK_Qw_TwY

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De Basabe, Jonás D., et Mrinal K. Sen. « Grid dispersion and stability criteria of some common finite-element methods for acoustic and elastic wave equations ». GEOPHYSICS 72, n^o 6 (novembre 2007) : T81—T95. http://dx.doi.org/10.1190/1.2785046.

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Purely numerical methods based on finite-element approximation of the acoustic or elastic wave equation are becoming increasingly popular for the generation of synthetic seismograms. We present formulas for the grid dispersion and stability criteria for some popular finite-element methods (FEM) for wave propagation, namely, classical and spectral FEM. We develop an approach based on a generalized eigenvalue formulation to analyze the dispersive behavior of these FEMs for acoustic or elastic wave propagation that overcomes difficulties caused by irregular node spacing within the element and the use of high-order polynomials, as is the case for spectral FEM. Analysis reveals that for spectral FEM of order four or greater, dispersion is less than 0.2% at four to five nodes per wavelength, and dispersion is not angle dependent. New results can be compared with grid-dispersion results of some classical finite-difference methods (FDM) used for acoustic or elastic wave propagation. Analysis reveals that FDM and classical FEM require a larger sampling ratio than a spectral FEM to obtain results with the same degree of accuracy. The staggered-grid FDM is an efficient scheme, but the dispersion is angle dependent with larger values along the grid axes. On the other hand, spectral FEM of order four or greater is isotropic with small dispersion, making it attractive for simulations with long propagation times.

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Müller, Andreas, Michal A. Kopera, Simone Marras, Lucas C. Wilcox, Tobin Isaac et Francis X. Giraldo. « Strong scaling for numerical weather prediction at petascale with the atmospheric model NUMA ». International Journal of High Performance Computing Applications 33, n^o 2 (5 avril 2018) : 411–26. http://dx.doi.org/10.1177/1094342018763966.

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Numerical weather prediction (NWP) has proven to be computationally challenging due to its inherent multiscale nature. Currently, the highest resolution global NWP models use a horizontal resolution of 9 km. At this resolution, many important processes in the atmosphere are not resolved. Needless to say, this introduces errors. In order to increase the resolution of NWP models, highly scalable atmospheric models are needed. The non-hydrostatic unified model of the atmosphere (NUMA), developed by the authors at the Naval Postgraduate School, was designed to achieve this purpose. NUMA is used by the Naval Research Laboratory, Monterey as the engine inside its next generation weather prediction system NEPTUNE. NUMA solves the fully compressible Navier–Stokes equations by means of high-order Galerkin methods (both spectral element as well as discontinuous Galerkin methods can be used). NUMA is capable of running middle and upper atmosphere simulations since it does not make use of the shallow-atmosphere approximation. This article presents the performance analysis and optimization of the spectral element version of NUMA. The performance at different optimization stages is analyzed using a theoretical performance model as well as measurements via hardware counters. Machine-independent optimization is compared to machine-specific optimization using Blue Gene (BG)/Q vector intrinsics. The best portable version of the main computations was found to be about two times slower than the best non-portable version. By using vector intrinsics, the main computations reach 1.2 PFlops on the entire IBM Blue Gene supercomputer Mira (12% of the theoretical peak performance). The article also presents scalability studies for two idealized test cases that are relevant for NWP applications. The atmospheric model NUMA delivers an excellent strong scaling efficiency of 99% on the entire supercomputer Mira using a mesh with 1.8 billion grid points. This allows running a global forecast of a baroclinic wave test case at a 3-km uniform horizontal resolution and double precision within the time frame required for operational weather prediction.

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Kadasch, Eckhard, Matthias Sühring, Tobias Gronemeier et Siegfried Raasch. « Mesoscale nesting interface of the PALM model system 6.0 ». Geoscientific Model Development 14, n^o 9 (3 septembre 2021) : 5435–65. http://dx.doi.org/10.5194/gmd-14-5435-2021.

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Abstract. In this paper, we present a newly developed mesoscale nesting interface for the PALM model system 6.0, which enables PALM to simulate the atmospheric boundary layer under spatially heterogeneous and non-stationary synoptic conditions. The implemented nesting interface, which is currently tailored to the mesoscale model COSMO, consists of two major parts: (i) the preprocessor INIFOR (initialization and forcing), which provides initial and time-dependent boundary conditions from mesoscale model output, and (ii) PALM's internal routines for reading the provided forcing data and superimposing synthetic turbulence to accelerate the transition to a fully developed turbulent atmospheric boundary layer. We describe in detail the conversion between the sets of prognostic variables, transformations between model coordinate systems, as well as data interpolation onto PALM's grid, which are carried out by INIFOR. Furthermore, we describe PALM's internal usage of the provided forcing data, which, besides the temporal interpolation of boundary conditions and removal of any residual divergence, includes the generation of stability-dependent synthetic turbulence at the inflow boundaries in order to accelerate the transition from the turbulence-free mesoscale solution to a resolved turbulent flow. We demonstrate and evaluate the nesting interface by means of a semi-idealized benchmark case. We carried out a large-eddy simulation (LES) of an evolving convective boundary layer on a clear-sky spring day. Besides verifying that changes in the inflow conditions enter into and successively propagate through the PALM domain, we focus our analysis on the effectiveness of the synthetic turbulence generation. By analysing various turbulence statistics, we show that the inflow in the present case is fully adjusted after having propagated for about two to three eddy-turnover times downstream, which corresponds well to other state-of-the-art methods for turbulence generation. Furthermore, we observe that numerical artefacts in the form of grid-scale convective structures in the mesoscale model enter the PALM domain, biasing the location of the turbulent up- and downdrafts in the LES. With these findings presented, we aim to verify the mesoscale nesting approach implemented in PALM, point out specific shortcomings, and build a baseline for future improvements and developments.

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Holt, Jason, Patrick Hyder, Mike Ashworth, James Harle, Helene T. Hewitt, Hedong Liu, Adrian L. New et al. « Prospects for improving the representation of coastal and shelf seas in global ocean models ». Geoscientific Model Development 10, n^o 1 (1 février 2017) : 499–523. http://dx.doi.org/10.5194/gmd-10-499-2017.

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Abstract. Accurately representing coastal and shelf seas in global ocean models represents one of the grand challenges of Earth system science. They are regions of immense societal importance through the goods and services they provide, hazards they pose and their role in global-scale processes and cycles, e.g. carbon fluxes and dense water formation. However, they are poorly represented in the current generation of global ocean models. In this contribution, we aim to briefly characterise the problem, and then to identify the important physical processes, and their scales, needed to address this issue in the context of the options available to resolve these scales globally and the evolving computational landscape.We find barotropic and topographic scales are well resolved by the current state-of-the-art model resolutions, e.g. nominal 1∕12°, and still reasonably well resolved at 1∕4°; here, the focus is on process representation. We identify tides, vertical coordinates, river inflows and mixing schemes as four areas where modelling approaches can readily be transferred from regional to global modelling with substantial benefit. In terms of finer-scale processes, we find that a 1∕12° global model resolves the first baroclinic Rossby radius for only ∼ 8 % of regions < 500 m deep, but this increases to ∼ 70 % for a 1∕72° model, so resolving scales globally requires substantially finer resolution than the current state of the art.We quantify the benefit of improved resolution and process representation using 1∕12° global- and basin-scale northern North Atlantic nucleus for a European model of the ocean (NEMO) simulations; the latter includes tides and a k-ε vertical mixing scheme. These are compared with global stratification observations and 19 models from CMIP5. In terms of correlation and basin-wide rms error, the high-resolution models outperform all these CMIP5 models. The model with tides shows improved seasonal cycles compared to the high-resolution model without tides. The benefits of resolution are particularly apparent in eastern boundary upwelling zones.To explore the balance between the size of a globally refined model and that of multiscale modelling options (e.g. finite element, finite volume or a two-way nesting approach), we consider a simple scale analysis and a conceptual grid refining approach. We put this analysis in the context of evolving computer systems, discussing model turnaround time, scalability and resource costs. Using a simple cost model compared to a reference configuration (taken to be a 1∕4° global model in 2011) and the increasing performance of the UK Research Councils' computer facility, we estimate an unstructured mesh multiscale approach, resolving process scales down to 1.5 km, would use a comparable share of the computer resource by 2021, the two-way nested multiscale approach by 2022, and a 1∕72° global model by 2026. However, we also note that a 1∕12° global model would not have a comparable computational cost to a 1° global model in 2017 until 2027. Hence, we conclude that for computationally expensive models (e.g. for oceanographic research or operational oceanography), resolving scales to ∼ 1.5 km would be routinely practical in about a decade given substantial effort on numerical and computational development. For complex Earth system models, this extends to about 2 decades, suggesting the focus here needs to be on improved process parameterisation to meet these challenges.

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TSAY, TING-KUEI, et FU-SENG HSU. « NUMERICAL GRID GENERATION OF AN IRREGULAR REGION ». International Journal for Numerical Methods in Engineering 40, n^o 2 (30 janvier 1997) : 343–56. http://dx.doi.org/10.1002/(sici)1097-0207(19970130)40:2<343 ::aid-nme68>3.0.co;2-c.

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Henshaw, William D. « Automatic grid generation ». Acta Numerica 5 (janvier 1996) : 121–48. http://dx.doi.org/10.1017/s0962492900002634.

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Current methods for the automatic generation of grids are reviewed. The approaches to grid generation that are discussed include Cartesian, multi-block-structured, overlapping and unstructured. Emphasis is placed on those methods that can create high-quality grids appropriate for the solution of equations of a hyperbolic nature, such as those that arise in fluid dynamics. Numerous figures illustrate the different grid generation techniques.

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Steinberg, Stanly, et Patrick J. Roache. « Variational grid generation ». Numerical Methods for Partial Differential Equations 2, n^o 1 (1986) : 71–96. http://dx.doi.org/10.1002/num.1690020107.

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Thèses sur le sujet "Numerical grid generation (Numerical analysis) Tides"

McDonald, Cameron L. « Automatic, Unstructured Mesh Generation for 2D Shelf Based Tidal Models ». Diss., CLICK HERE for online access, 2006. http://contentdm.lib.byu.edu/ETD/image/etd1550.pdf.

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McMorris, Harlan Tom. « Towards hybrid mesh generation for realistic design environments / ». Digital version:, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p9992870.

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Raghu, K. K. « Automatic mesh generation and finite element analysis of a triax dome ». Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03122009-040414/.

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Yan, Dongming. « Variational shape segmentation and mesh generation ». Click to view the E-thesis via HKUTO, 2010. http://sunzi.lib.hku.hk/hkuto/record/B43932514.

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Yan, Dongming, et 严冬明. « Variational shape segmentation and mesh generation ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B43932514.

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Khawaja, Aly Salim. « General semi-structured grid generation for complex 3-D geometries with disparate length scales / ». Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.

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Zhang, Hanzhou. « Mesh generation for voxel-based objects ». Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4148.

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Thesis (Ph. D.)--West Virginia University, 2005.
Title from document title page. Document formatted into pages; contains x, 121 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 110-121).

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Boubez, Toufic I. « Three-dimensional finite-element mesh generation using serial sections ». Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63804.

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Pinchuk, Amy Ruth. « Automatic adaptive finite element mesh generation and error estimation ». Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63269.

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Sinha, Bhaskar. « Surface mesh generation using curvature-based refinement ». Master's thesis, Mississippi State : Mississippi State University, 2002. http://library.msstate.edu/etd/show.asp?etd=etd-09252002-141359.

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Livres sur le sujet "Numerical grid generation (Numerical analysis) Tides"

Liseĭkin, V. D. Grid generation methods. Berlin : Springer, 1999.

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Knupp, Patrick M. The fundamentals of grid generation. Boca Raton : CRC Press, 1993.

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Jameson, Leland M. Wavelet-based grid generation. Hampton, Va : National Aeronautics and Space Administration, Langley Research Center, 1996.

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A, Warsi Z. U., et Mastin C. Wayne, dir. Numerical grid generation : Foundations and applications. New York : North-Holland, 1985.

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Alsalihi, Zuheyr. Two dimensional hyperbolic grid generation. Rhode Saint Genese, Belgium : von Karman Institute for Fluid Dynamics, 1987.

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Mastin, C. Wayne. Application of three-dimensional Be zier patches in grid generation. [Washington, DC : National Aeronautics and Space Administration, 1990.

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M, David. TIGGERC--turbomachinery interactive grid generator for 2-D grid applications and uers guide. [Washington, D.C.] : National Aeronautics and Space Administration, 1994.

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Thompson, Joe F. Enhancement of surface definition and gridding in the Eagle code : Final report. Mississippi State, MS : Mississippi State University, Engineering Research Center for Computational Field Simulation, Complex Geometry/Complex Physics, 1991.

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Nguyen, Hung Lee. On the applications of algebraic grid generation methods based on transfinite interpolation. [Washington, DC] : National Aeronautics and Space Administration, 1989.

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Edwards, Thomas A. Geometry definition and grid generation for a complete fighter aircraft. Moffett Field, Calif : National Aeronautics and Space Administration, Ames Research Center, 1986.

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Chapitres de livres sur le sujet "Numerical grid generation (Numerical analysis) Tides"

Dey, Bishwajit, Biplab Bhattacharyya et Sharmistha Sharma. « Robust Economic Dispatch of Microgrid With Highly Penetrated Renewables and Energy Storage System ». Dans Research Anthology on Clean Energy Management and Solutions, 303–23. IGI Global, 2021. http://dx.doi.org/10.4018/978-1-7998-9152-9.ch014.

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Economic dispatch (ED) of a grid-connected and renewable integrated microgrid is considered in this article. Here, the renewable energy sources (RES) taken into consideration are wind farms. A parameter worst-case-transaction-cost which arises due to the stochastic availability and uncontrollable nature of wind farms is also emphasised and efforts have been taken to minimize it too. Hence, the article focuses on separately optimizing the generation costs and the worst-case transaction costs. It also optimises the net microgrid cost as a whole, which is the summation of generation costs and the worst-case transaction costs. Two different cases with highly varying transaction prices are studied. Various types of loads, ramp rates of generators, charging and discharging limits of the batteries are taken into consideration while minimizing the microgrid cost. Four meta-heuristic soft computing algorithms are applied for optimization and a comparative analysis among them is studied. Numerical results are tabulated to justify the effectiveness of the novel approach.

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Actes de conférences sur le sujet "Numerical grid generation (Numerical analysis) Tides"

Sulman, Mohamed, J. F. Williams, Robert D. Russell, Theodore E. Simos, George Psihoyios et Ch Tsitouras. « Monge-Kantorovich Approach for Grid Generation ». Dans NUMERICAL ANALYSIS AND APPLIED MATHEMATICS : International Conference on Numerical Analysis and Applied Mathematics 2009 : Volume 1 and Volume 2. AIP, 2009. http://dx.doi.org/10.1063/1.3241442.

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Chiappini, D., et A. Donno. « A comparison between different fractal grid generation methods coupled with lattice Boltzmann approach ». Dans INTERNATIONAL CONFERENCE OF NUMERICAL ANALYSIS AND APPLIED MATHEMATICS 2015 (ICNAAM 2015). Author(s), 2016. http://dx.doi.org/10.1063/1.4952042.

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Guyot, Marc, Cyrille De Mourgues, Gérard Le Bihan, Pierre Parenthoine, Julien Templai, Aengus Connolly et Marc Le Boulluec. « Experimental Offshore Floating Wind Turbine Prototype and Numerical Analysis During Harsh and Production Events ». Dans ASME 2019 2nd International Offshore Wind Technical Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/iowtc2019-7602.

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Abstract EOLINK have developed an innovative floating wind turbine in which the single tower is replaced by a set of legs providing a pyramidal architecture. A 1/10th scale prototype of EOLINK’s 12MW concept has been connected to the grid in April 2018 in France. Firstly, the paper describes the technical specifications of this device. Both the turbine and the floater have been designed using Froude scaling, in order to properly represent the EOLINK full scale 12MW concept. The device has been devised from scratch and deploys a Permanent Magnet Synchronous Generator (PMSG) and an individual electric blade pitch system. The patented mooring system comprises a single point mooring (SPM) system able to withstand very high tide ranges in shallow waters. Regarding monitoring, motions have been recorded using both an Inertial Measurement Unit (IMU) and high precision Global Positioning System (GPS) sensors. Mooring lines tensions have also been monitored. Wind is recorded using both an embedded anemometer on the floating turbine and onshore anemometers installed by IFREMER. This Institute has also measured wave height using a wave recorder. Secondly, experimental results during production and storm events are presented. The encountered environmental conditions highlight the capability of the EOLINK design to withstand harsh wind events, and its ability to produce 12MW using a small sized semi-submersible floater. Then, numerical analysis using FAST and Flexcom is compared with experimental results. Static analysis, decay-tests, Response Amplitude Operators (RAOs) and Power Spectral Densities (PSDs) results are detailed. Power production and the embedded control command capabilities are also presented.

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Sahrani, Shafrida, et Michiko Kuroda. « Numerical analysis of the electromagnetic wave scattering from a moving dielectric body by Overset Grid Generation method ». Dans 2012 IEEE Asia-Pacific Conference on Applied Electromagnetics (APACE). IEEE, 2012. http://dx.doi.org/10.1109/apace.2012.6457621.

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Bahrainian, Seyed Saied, et Zahra Mehrdoost. « A Novel Hybrid Approach for Unstructured Viscous Grid Generation ». Dans ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis. ASMEDC, 2010. http://dx.doi.org/10.1115/esda2010-24325.

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Accurate solution of boundary layer and wake flow require generation of high aspect ratio grids in these regions. A hybrid approach for the efficient generation of inviscid and viscous unstructured grids has been introduced. A novel feature of the current work is its ability to produce boundary layer and wake grids that enables accurate flow solutions in viscous flow regions. The grid generation algorithm starts with a very coarse initial grid. In the inviscid region, isotropic cells of excellent quality are produced using a combination of point insertion and cell subdivision techniques. Simultaneously, a directional grid refinement strategy is used to construct highly stretched triangular cells in viscous regions. First, anisotropic unstructured grids are produced in the stream wise direction. Then, cells close to the solid surface are refined to highly stretched layer of triangles suitable for boundary layer region. Smooth transition between the boundary layer grid and the outer isotropic grid is easily obtained with a user specified cell size and stretch. The accuracy of the current grid generation approach is assessed by laminar and turbulent compressible flow solutions around NACA0012 and RAE2822 airfoils. The results of the numerical flow simulations are compared with published experimental and numerical data. Comparisons point to the ability of the proposed unstructured boundary layer and wake grid generation procedure.

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Yang, H., D. Nuernberger, E. Nicke et A. Weber. « Numerical Investigation of Casing Treatment Mechanisms With a Conservative Mixed-Cell Approach ». Dans ASME Turbo Expo 2003, collocated with the 2003 International Joint Power Generation Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/gt2003-38483.

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A conservative mixed-cell approach of second-order accuracy is presented and applied to investigate the mechanisms of a self-recirculating casing treatment coupled with a transonic compressor rotor. The mixed cell is a computational cell that may show up at the zonal interface boundary, the face of which is partially solid and partially fluid, if the azimuthal open area of casing treatment does not fully contact with the whole annulus of blade passage. The mixed-cell approach is essentially an extension of the conservative zonal approach by incorporating special mixed-cell handling at the zonal interface and it allows a great flexibility to the grid generation for the patched zones with the best grid topology. The mixed-cell approach is extremely useful for solving the unsteady interaction problems within turbomachinery and its application for simulating the coupled flow through the rotor and the casing treatment is reported. The calculated results and analysis reveal an effective stall margin extension of the casing treatment herein by weakening or even destroying the tip leakage vortex, and expose the different tip flow topologies between the cases with the casing treatment and with the untreated smooth wall. It is found that the casing treatment only slightly decreases the overall efficiency at the design point, but it is beneficial to the overall efficiency at the off-design operating conditions and it can improve the inflow conditions to the downstream stator blade row as well.

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Cândido, Sílvio, et José C. Páscoa. « Numerical Analysis on the Stability Conditions of an Electrohydrodynamic Jet ». Dans ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-24101.

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Abstract The Taylor cone jet is a well-known electrohydrodynamic flow (EHD), usually produced by applying an external electric field to a capillary liquid. The generation of this kind of flow involves a multi-phase and a multi-physics process and its stability has a specific operation window. This operating window is intrinsically dependent on the flow rate and magnitude of the applied electric voltage. In case high voltages are applied to the jet it can atomize and produce an electrospray. Our work presents a numerical study of the process of atomization of a Taylor cone jet using computational fluid dynamics (CFD). The study intents to assess the limit conditions of operation and the applied voltage needed to stabilize an electrospray. The numerical model was implemented within OpenFOAM, where the multi-phase hydrodynamics equations are solved using a volume-of-fluid (VOF) approach. This method is coupled with the Maxwell equations governing an electrostatic field, in order to incorporate the electric body forces into the incompressible Navier-Stokes equations. The leaky-dielectric model is used and, therefore, the interface between the two phases is subject to the hydrodynamic surface tension and electric stress (Maxwell stress). This allows a leakage of charge though the phase due to ohmic conduction. Thus, the permittivity and conductivity of the phases are taken into consideration. A two-fluid system with relevant electric properties can be categorized as, dielectric-dielectric, dielectric-conducting, and conducting-conducting considering the electrical conductivity and permittivities of the participating phases. Due to the usage of the leaky-dielectric model, it is possible to simulate any of this physical situations. By increasing the applied voltage reaches a value where the cone instability is verified, allowing a discussion on this effect. It is demonstrated that to adequately model the process of atomization a fine grid refinement is needed. The validation of the numerical model is made by comparing against diverse experimental data, for the case of a stable jet. The diameter and velocity of the droplet and the electric current of the jet are the main variables that are compared with previous results. The tests were performed with Heptane. The cone and the jet are strongly affected by the flow rate. The dimensionless diameter, as a function of the dimensionless flow rate, agrees with the scaling laws. The model predicts accurate results over a wide range of flow rates with an accuracy of around 10%. The results are obtained using structured meshes.

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Basson, A., et B. Lakshminarayana. « Numerical Simulation of Tip Clearance Effects in Turbomachinery ». Dans ASME 1993 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1993. http://dx.doi.org/10.1115/93-gt-316.

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The numerical formulation developed here includes an efficient grid generation scheme, particularly suited to computational grids for the analysis of turbulent turbomachinery flows and tip clearance flows, and a semi-implicit, pressure-based computational fluid dynamics scheme that directly includes artificial dissipation, and is applicable to both viscous and inviscid flows. The values of these artificial dissipation is optimized to achieve accuracy and convergency in the solution. The numerical model is used to investigate the structure of tip clearance flows in a turbine nozzle. The structure of leakage flow is captured accurately, including blade-to-blade variation of all three velocity components, pitch and yaw angles, losses and blade static pressures in the tip clearance region. The simulation also includes evaluation of such quantities of leakage mass flow, vortex strength, losses, dominant leakage flow regions and the spanwise extent affected by the leakage flow. It is demonstrated, through optimization of grid size and artificial dissipation, that the tip clearance flow field can be captured accurately.

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Saha, Pankaj, Peter Strakey, Donald Ferguson et Arnab Roy. « Numerical Analysis of Detonability Assessment in a Natural Gas-Air Fueled Rotating Detonation Engine ». Dans ASME 2019 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/imece2019-11728.

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Abstract Rotating Detonation Engines (RDE) offer an alternative combustion strategy to replace conventional constant pressure combustion with a process that could produce a pressure gain without the use of a mechanical compressor. Recent numerical and experimental publications that consider air as the oxidizer have primarily focused on the ability of these annular combustors to sustain a stable continuous detonation wave when fueled by hydrogen. However, for this to be a viable consideration for the land-based power generation it is necessary to explore the ability to detonate natural gas and air within the confines of the annular geometry of an RDE. Previous studies on confined detonations have expressed the importance of permitting detonation cells to fully form within the combustor in order to achieve stability. This poses a challenge for natural gas–air fueled processes as their detonation cell size can be quite large even at moderate pressures. Despite the practical importance, only a few studies are available on natural gas detonations for air-breathing RDE applications. Moreover, the extreme thermodynamic condition (high temperature inside the combustor) allows limited accessibility inside the combustor for detailed experimental instrumentations, providing mostly single-point data. Recent experimental studies at the National Energy Technology Laboratory (NETL) have reported detonation failure at higher methane concentration in an air-breathing RDE fueled by natural gas-hydrogen fuel blends. This encourages to perform a detailed numerical investigation on the wave characteristics of detonation in a natural gas-air fueled RDE to understand the various aspects of instability associated with the natural gas-air detonation. This study is a numerical consideration of a methane-air fueled RDE with varying operating conditions to ascertain the ability to achieve a stable, continuous detonation wave. The simulations have been performed in a 2D unwrapped RDE geometry using the open-source CFD library “OpenFOAM” employing an unsteady pressure-based compressible reactive flow solver with a k–ε turbulence model in a structured rectangular grid system. Both reduced and detailed chemical kinetic models have been used to assess the effect of the chemistry on the detonation wave characteristics and the underlying flow features. A systematic grid sensitivity study has been conducted with various grid sizes to quantify the weakly stable overdriven detonation on a coarse mesh and oscillating features at fine mesh resolutions. The main focus of the current study is to investigate the effects of operating injection pressure on detonation wave characteristics of an air-breathing Rotating Detonation Engine (RDE) fueled with natural gas-hydrogen fuel blends. Wave speeds, peak pressures and temperatures, and dominant frequencies have been computed from the time histories. The flow structures were then visualized using 2D contours of temperature and species concentration.

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Hecker, Philipp, Damir Delimar, Herbert Brandl et Michael Lo¨tzerich. « Process Integration and Automated Numerical Design Optimization of an Eigenfrequency Analysis of a Compressor Blade ». Dans ASME 2011 Turbo Expo : Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-45489.

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Modern gas turbines for applications in power plants have to fulfill more and more demands defined by customer and grid requirements. These requirements address for example reduced time for run up and increased power output while providing maximum single or combined cycle efficiency. The demanding market requirements increase the pressure to further improve the design process of gas turbine parts by reducing the overall development time and simultaneously improving the quality of the design. This paper describes the implementation of an automated optimization process for the mechanical assessment of compressor blades applied during the preliminary design process. Previous work from Fedorov, Szwedowicz, et al [1], has shown that it is important to apply 3D FE methods for the accurate prediction of the dynamic behavior of compressor blades already in the early stage of the design phase. These key ideas were picked up in the present work while the FE model from [1] was extended to a complete 3D model of the compressor blade including airfoil and blade root geometry. The new approach completely automates the 3D FE analysis of compressor blades including CAD model generation, FE pre-processing, FE analyses, FE post-processing and takes it to the further level by integrating the FE analysis procedure into an automated design loop using the commercial optimization software iSight FD. The target of this optimization loop is to drive the frequency of critical mode shapes into allowed ranges by modifying airfoil parameters such as airfoil thickness and chord length. A scalar optimization technique is applied solving the design problem using penalty functions for excitation sources, mode shapes and eigenfrequencies. In order to achieve a smooth distribution of airfoil parameters Bezier-Spline approximations are used to parameterize the design space. The implementation of the mechanical analysis for compressor blades into a standardized and automated process was one of the main achievements of the presented work. The process was completely implemented in Abaqus CAE including 3D FE model preparation and post-processing. It was key to a successful integration into an overall optimization loop, which helped to substantially reduce the amount of manual work required to perform the design task.

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