Academic literature on the topic 'Lagrangian Dynamic Smagorinsky model'
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Journal articles on the topic "Lagrangian Dynamic Smagorinsky model"
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Efstathiou, G. A., R. S. Plant, and M. J. M. Bopape. "Simulation of an Evolving Convective Boundary Layer Using a Scale-Dependent Dynamic Smagorinsky Model at Near-Gray-Zone Resolutions." Journal of Applied Meteorology and Climatology 57, no. 9 (September 2018): 2197–214. http://dx.doi.org/10.1175/jamc-d-17-0318.1.
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AbstractA scale-dependent Lagrangian-averaged dynamic Smagorinsky subgrid scheme with stratification effects is used to simulate the evolving convective boundary layer of the Wangara (Australia) case study in the gray-zone regime (specifically, for grid lengths from 25 to 400 m). The dynamic Smagorinsky and standard Smagorinsky approaches are assessed for first- and second-order quantities in comparison with results derived from coarse-grained large-eddy simulation (LES) fields. In the LES regime, the subgrid schemes produce very similar results, albeit with some modest differences near the surface. At coarser resolutions, the use of the standard Smagorinsky approach significantly delays the onset of resolved turbulence, with the delay increasing with coarsening resolution. In contrast, the dynamic Smagorinsky scheme much improves the spinup and so is also able to maintain consistency with the LES temperature profiles at the coarser resolutions. Moreover, the resolved part of the turbulence reproduces well the turbulence profiles obtained from the coarse-grained fields, especially in the near gray zone. The dynamic scheme does become somewhat overenergetic with further coarsening of the resolution, especially near the surface. The dynamic scheme reaches its limit in the current configuration when the test filter starts to sample at the unresolved scales, returning very small Smagorinsky coefficients. Sensitivity tests reveal that the dynamic model can adapt to changes in the imposed numerical or subgrid diffusion by adjusting the Smagorinsky constant to the changing flow field and minimizing the dissipation effects on the resolved turbulence structures.
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Kirkil, Gokhan, Jeff Mirocha, Elie Bou-Zeid, Fotini Katopodes Chow, and Branko Kosović. "Implementation and Evaluation of Dynamic Subfilter-Scale Stress Models for Large-Eddy Simulation Using WRF*." Monthly Weather Review 140, no. 1 (January 1, 2012): 266–84. http://dx.doi.org/10.1175/mwr-d-11-00037.1.
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Abstract The performance of a range of simple to moderately-complex subfilter-scale (SFS) stress models implemented in the Weather Research and Forecasting (WRF) model is evaluated in large-eddy simulations of neutral atmospheric boundary layer flow over both a flat terrain and a two-dimensional symmetrical transverse ridge. Two recently developed dynamic SFS stress models, the Lagrangian-averaged scale-dependent (LASD) dynamic model and the dynamic reconstruction model (DRM), are compared with the WRF model’s existing constant-coefficient linear eddy-viscosity and (as of version 3.2) nonlinear SFS stress models to evaluate the benefits of more sophisticated and accurate, but also more computationally expensive approaches. Simulation results using the different SFS stress models are compared among each other, as well as against the Monin–Obukhov similarity theory. For the flat terrain case, vertical profiles of mean wind speed from the newly implemented dynamic models show the best agreement with the similarity solution, improving even upon the nonlinear model, which likewise yields a significant improvement compared to the Smagorinsky model. The more sophisticated SFS stress models more successfully predict the expected production and inertial range scaling of power spectra, especially near the surface, with the dynamic models achieving the best scaling overall. For the transverse ridge case, the nonlinear model predicts the greatest amount of reverse flow in the lee of the ridge, and also demonstrates the greatest ability to duplicate qualitative features of the highest-resolution simulations at coarser resolutions. The dynamic models’ flow distributions in the lee of the ridge did not differ significantly from the constant-coefficient Smagorinsky model.
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IIZUKA, Satoru, Shuzo MURAKAMI, Akashi MOCHIDA, Yoshihide TOMINAGA, Hikaru KOBAYASHI, and Squires K. D. "PERFORMANCE OF LAGRANGIAN DYNAMIC SMAGORINSKY MODEL : Large eddy simulation of turbulent flow past 2D square cylinder using dynamic SGS model (Part 3)." Journal of Architecture and Planning (Transactions of AIJ) 63, no. 511 (1998): 39–43. http://dx.doi.org/10.3130/aija.63.39_5.
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Pitchurov, George, Christof Gromke, Jordan A. Denev, and Flavio Cesar Cunha Galeazzo. "Validation study for Large-Eddy Simulation of Forest Flow." E3S Web of Conferences 207 (2020): 02010. http://dx.doi.org/10.1051/e3sconf/202020702010.
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The publication presents Large-Eddy Simulation (LES) of flow over a reduced-scale wind tunnel model of a forest canopy. The final aim of the study is to determine factors responsible for damage in forests by strong winds. The wind tunnel forest was represented by an open-porous foam material for the crown layer and wooden dowels for the trunk layer. The forest model was installed in the open test section of a Goettingen-type wind tunnel and Particle Image Velocimetry (PIV) measurements were made for the acquisition of the flow field data. The numerical simulations were performed with OpenFOAM®. The forest was modelled by an additional sink term in the momentum transport equations based on the leaf area density and a characteristic drag coefficient for the underlying tree specimen. Large-eddy simulations with different subgrid-scale (SGS) turbulence models were carried out and compared to wind tunnel data. The Smagorinsky SGS model outperformed the dynamic Lagrangian SGS model in the windward edge region (within a distance of approximately 2 tree heights from the leading edge) whereas the dynamic Lagrangian SGS model showed a better performance for regions farther downstream.
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Rismondo, Giacomo, Marta Cianferra, and Vincenzo Armenio. "Acoustic Response of a Vibrating Elongated Cylinder in a Hydrodynamic Turbulent Flow." Journal of Marine Science and Engineering 10, no. 12 (December 6, 2022): 1918. http://dx.doi.org/10.3390/jmse10121918.
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The present paper contains the results of the numerical analysis of the interaction between a Newtonian incompressible turbulent flow and a linear elastic slender body, together with the influence of the fluid–structure interaction (FSI) on the noise generation and propagation. The purpose is to evaluate the differences in term of acoustic pressure between the case where the solid body is rigid (infinite stiffness) and the case where it is elastic (finite stiffness). A partitioned and implicit algorithm with the arbitrary Lagrangian–Eulerian method (ALE) is used for the interaction between the fluid and solid. For the evaluation of the turbulent fluid motion, we use a large eddy simulation (LES) with the Smagorinsky subgrid scale model. The equation for the solid is solved through the Lagrangian description of the momentum equation and the second Piola–Kirchoff stress tensor. In addition, the acoustic analogy of Lighthill is used to characterize the acoustic source (the slender body) by directly using the fluid dynamic fields. In particular, we use the Ffowcs Williams and Hawkings (FW-H) equation for the evaluation of the acoustic pressure in the fluid medium. As a first numerical experiment, we analyze a square cylinder immersed in a turbulent flow characterized by two different values of stiffness: one infinite (rigid case) and one finite (elastic case). In the latter case, the body stiffness and mean flow velocity are such that they induce the lock-in phenomenon. Finally, we evaluate the differences in terms of acoustic pressure between the two different cases.
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Scotti, A., C. Meneveau, and M. Fatica. "Dynamic Smagorinsky model on anisotropic grids." Physics of Fluids 9, no. 6 (June 1997): 1856–58. http://dx.doi.org/10.1063/1.869306.
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Khani, Sina, and Michael L. Waite. "Large eddy simulations of stratified turbulence: the dynamic Smagorinsky model." Journal of Fluid Mechanics 773 (May 21, 2015): 327–44. http://dx.doi.org/10.1017/jfm.2015.249.
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The dynamic Smagorinsky model for large eddy simulation (LES) of stratified turbulence is studied in this paper. A maximum grid spacing criterion of ${\it\Delta}/L_{b}<0.24$ is found in order to capture several of the key characteristics of stratified turbulence, where ${\it\Delta}$ is the filter scale and $L_{b}$ is the buoyancy scale. These results show that the dynamic Smagorinsky model needs a grid spacing approximately twice as large as the regular Smagorinsky model to reproduce similar results. This improvement on the regular Smagorinsky eddy viscosity approach increases the accuracy of results at small resolved scales while decreasing the computational costs because it allows larger ${\it\Delta}$. In addition, the eddy dissipation spectra in LES of stratified turbulence present anisotropic features, taking energy out of large horizontal but small vertical scales. This trend is not seen in the non-stratified cases, where the subgrid-scale energy transfer is isotropic. Statistics of the dynamic Smagorinsky coefficient $c_{s}$ are investigated; its distribution is peaked around zero, and its standard deviations decrease slightly with increasing stratification. In line with previous findings for unstratified turbulence, regions of increased shear favour smaller $c_{s}$ values; in stratified turbulence, the spatial distribution of the shear, and hence $c_{s}$, is dominated by a layerwise pancake structure. These results show that the dynamic Smagorinsky model presents a promising approach for LES when isotropic buoyancy-scale resolving grids are employed.
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Schaefer-Rolffs, Urs, and Erich Becker. "Horizontal Momentum Diffusion in GCMs Using the Dynamic Smagorinsky Model." Monthly Weather Review 141, no. 3 (March 1, 2013): 887–99. http://dx.doi.org/10.1175/mwr-d-12-00101.1.
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Abstract A dynamic version of Smagorinsky’s diffusion scheme is presented that is applicable for large-eddy simulations (LES) of the atmospheric dynamics. The approach is motivated (i) by the incompatibility of conventional hyperdiffusion schemes with the conservation laws, and (ii) because the conventional Smagorinsky model (which fulfills the conservation laws) does not maintain scale invariance, which is mandatory for a correct simulation of the macroturbulent kinetic energy spectrum. The authors derive a two-dimensional (horizontal) formulation of the dynamic Smagorinsky model (DSM) and present three solutions of the so-called Germano identity: the method of least squares, a solution without invariance of the Smagorinsky parameter, and a tensor-norm solution. The applicability of the tensor-norm approach is confirmed in simulations with the Kühlungsborn mechanistic general circulation model (KMCM). The standard spectral dynamical core of the model facilitates the implementation of the test filter procedure of the DSM. Various energy spectra simulated with the DSM and the conventional Smagorinsky scheme are presented. In particular, the results show that only the DSM allows for a reasonable spectrum at all scales. Latitude–height cross sections of zonal-mean fluid variables are given and show that the DSM preserves the main features of the atmospheric dynamics. The best ratio for the test-filter scale to the resolution scale is found to be 1.33, resulting in dynamically determined Smagorinsky parameters cS from 0.10 to 0.22 in the troposphere. This result is very similar to other values of cS found in previous three-dimensional applications of the DSM.
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Schaefer-Rolffs, Urs. "A generalized formulation of the dynamic Smagorinsky model." Meteorologische Zeitschrift 26, no. 2 (April 25, 2017): 181–87. http://dx.doi.org/10.1127/metz/2016/0801.
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Wang, T., G. Tao, J. S. Bai, P. Li, and B. Wang. "Numerical comparative analysis of Richtmyer–Meshkov instability simulated by different SGS models." Canadian Journal of Physics 93, no. 5 (May 2015): 519–25. http://dx.doi.org/10.1139/cjp-2014-0099.
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The multi-mode Richtmyer–Meshkov instability is numerically simulated by the large-eddy simulation code MVFT (multi-viscous-flow and turbulence). The Vreman, dynamic Smagorinsky, and stretched-vortex models are used to model the subgrid-scale flux of turbulence transport in simulations. The calculated widths of turbulent mixing zones are all in good agreement with the experimental results, and there is a little difference among the different SGS models. However, the decay factors of turbulent kinetic energy differ significantly for different SGS models, with relative error up to about 50%. It is concluded that the dynamic Smagorinsky model and stretched-vortex model can both predict the energy backscatter, with the prediction of the former weaker, while after reshock, the dynamic Smagorinsky model is absolutely as dissipative as the Vreman model.
Dissertations / Theses on the topic "Lagrangian Dynamic Smagorinsky model"
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Foroozani, Najmeh. "Numerical Study of Turbulent Rayleigh-Benard Convection with Cubic confinement." Doctoral thesis, Università degli studi di Trieste, 2015. http://hdl.handle.net/10077/11115.
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2012/2013Turbulent Rayleigh-Bénard convection (RBC) occurs when a shallow layer of fluid is heated from below. It is a challenging subject in non-linear physics, with many important applications in natural and engineering systems. Because of the complexity of the governing equations, analytical progress in understanding convection has been slow, and laboratory experiments and numerical simulations have assumed increased importance. In regard to numerical work, Large-Eddy Simulation (LES) techniques have proved to be reliable and powerful tool to understand the physics since it provides better coverage for measurements, that are not as easily obtained in physical experiments or the other numerical approaches. This thesis addresses different aspects of Rayleigh-Bénard convection in fully developed turbulent regime through Large Eddy Simulation (LES) to shed light on some important aspect of the geometrical shape of the convection cell. The layout of the thesis is as follows: In Chapter 1, we first introduce Rayleigh-Bénard convection and the equations and parameters that govern it. This is followed by a discussion on different types of boundary conditions used in numerical and theoretical studies of RBC. Subsequently we present various convection states that are observed analytically and experimentally in RBC as a function of Ra and Ʈ. To this end we present a brief survey of the analytical, experimental and numerical works on confined thermal convection. We introduce different regimes and related scaling according to Grossman and Lohse theory. We also present the experimental and numerical results related to the Large Scale Circulation (LSC) within different geometries. In Chapter 2, we present the details of the numerical methods used to solve the governing non-linear equations . In the second part, we provide the details of the solver and the algorithm used to solve the RBC dynamical equations in a Cartesian geometry together with boundary conditions. In Chapter 3, we demonstrate that our numerical method and solver give results consistent with earlier numerical results. Results from the Direct Numerical Simulations (DNS) and Large Eddy Simulation (LES) with constant and dynamic subgrid scale Prandtl number (P_sgs) are presented and compared. We observe close agreement with Lagrangian dynamic approaches. In the first part of Chapter 4 we analyse the local fluctuations of turbulent Rayleigh-Bénard convection in a cubic confinement with aspect ratio one for Prandtl number Pr = 0.7 and Rayleigh numbers (Ra) up to 10^9 by means of LES methodology on coarse grids. Our results reveal that the scaling of the root-mean-square density and velocity fluctuations measured in the cell center are in excellent agreement with the unexpected scaling measured in the laboratory experiments of Daya and Ecke (2001) in their square cross-section cell. Moreover we find that the time-averaged spatial distributions of density fluctuations show a fixed inhomogeneity that maintains its own structure when the flow switches from one diagonal to the other. The largest level of rms density fluctuations corresponds to the diagonal opposite that of the Large Scale Circulation (LSC) where we observed strong counter-rotating vortex structures. In the second part we extended our simulations and Ra up to 1011, in order to identify the time periods in which the orientation of LSC is constant. Surprisingly we find that the LSC switches stochastically from one diagonal to the other. In Chapter 5, we study the effect of 3D-roughness on scaling of Nu(Ra) and consequently on the fluctuations of density. Moreover we present the effect of roughness shape when the tip has a wide angle and the other one is smooth. We study two types of elements, one of which is a pyramid and the other is a sinusoidal function spread over the bottom (heated) and top (cooled) plates, in a cubic confinement. However preliminary results suggest that the effect of roughness appears evident at high Ra numbers when the thermal boundary layer is thin enough to shape around the obstacles.
XXVI Ciclo
1983
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Abrahamowicz, Maria Izabela. "A thermodynamic and dynamic Lagrangian model for icebergs: a data-model intercomparison for the Southern Ocean." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18677.
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A Lagrangian dynamic and thermodynamic iceberg drift model was developed, coded and validated against observations. First, the model was used to create a climatology (1979-2000) of iceberg drift in the Southern Ocean. The simulation reproduced the main patterns of motion and the northernmost extent of Antarctic icebergs as inferred from satellite and ship observations. The model was then used to hindcast 29 giant iceberg drift tracks in what was the first study of an iceberg model ability to reproduce the motion of individual icebergs around the Antarctic continent on timescales of years. The shape and timing of twelve of the twenty-nine tracks was successfully modeled with a model error in the 0.9-50% range. In six cases, the shape of the observed drift track was reproduced but the timing was off, and in the remaining eleven simulation the icebergs moved in the wrong direction. The model error was found to be independent of simulation length suggesting that the error was due to inaccuracies in the forcing data rather than in the physics of the model. In particular, model performance deteriorated in coastal areas and in the southern portions of the Weddell and Ross sea, highlighting the need for higher resolution forcing data in these regions. The model accuracy would benefit from a better definition of the Antarctic coastline, a better representation of Katabatic winds off the continent and a forcing ocean model which would include a dynamic and thermodynamic sea-ice component.Un modèle Lagrangien dynamique-thermodynamique pour la dérive d'icebergs a été développé, codé et validé à l'aide d'observations. Premièrement, nous avons produit, à l'aide du modèle, une climatologie (1979-2000) de la dérive d'icebergs dans l'Océan du Sud. Les principales tendances du mouvement des icebergs simulés sont en accord avec les observations satellitaires et les mesures in-situ. Le modèle simule bien la limite septentrionale des icebergs d'Antarctique. Nous avons ensuite simulé vingt-neuf trajectoires individuelles d'icebergs géants. C'est la première fois qu'une telle étude est menée pour des icebergs observés autour de l'Antarctique et sur une échelle de plusieurs années. Dans douze cas, le tracé et le minutage de la trajectoire observée a été reproduit avec succès (erreur de 0.9-50%). Six simulations avaient des erreurs de temps mais non de trajet et dans les onze simulations restantes, l'iceberg a dérivé dans la mauvaise direction. Il a été établi que l'erreur du modèle était indépendante de la durée de la simulation, suggérant que l'erreur était due au champ de forçage plutôt qu'aux équations physiques du modèle. En particulier, une détérioration de la qualité des résultats a été observée dans les régions côtières et dans les parties sud des mers de Ross et de Weddell; soulignant ainsi le besoin d'améliorer le champ de forçage dans ces régions. D'autres moyens d'augmenter la précision du modèle seraient, entre autre, une meilleure définition de la géographie côtière de l'Antarctique, une meilleure représentation des vents catabatiques et un modèle océanique incluant une composante de glace dynamique et thermodynamique.
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Gonc, L. Oktay. "Computation Of External Flow Around Rotating Bodies." Phd thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605985/index.pdf.
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A three-dimensional, parallel, finite volume solver which uses Roe's upwind flux differencing scheme for spatial and Runge-Kutta explicit multistage time stepping scheme for temporal discretization on unstructured meshes is developed for the unsteady solution of external viscous flow around rotating bodies. The main aim of this study is to evaluate the aerodynamic dynamic stability derivative coefficients for rotating missile configurations. Arbitrary Lagrangian Eulerian (ALE) formulation is adapted to the solver for the simulation of the rotation of the body. Eigenvalues of the Euler equations in ALE form has been derived. Body rotation is simply performed by rotating the entire computational domain including the body of the projectile by means of rotation matrices. Spalart-Allmaras one-euqation turbulence model is implemented to the solver. The solver developed is first verified in 3-D for inviscid flow over two missile configurations. Then inviscid flow over a rotating missile is tested. Viscous flux computation algorithms and Spalarat-Allmaras turbulence model implementation are validated in 2-D by performing calculations for viscous flow over flat plate, NACA0012 airfoil and NLR 7301 airfoil with trailing edge flap. The ALE formulation is validated in 2-D on a rapidly pitching NACA0012 airfoil. Afterwards three-dimensional validation studies for viscous, laminar and turbulent flow calculations are performed on 3-D flat plate problem. At last, as a validation test case, unsteady laminar and turbulent viscous flow calculations over a spinning M910 projectile configuration are performed. Results are qualitatively in agreement with the analytical solutions, experimental measurements and previous studies for steady and unsteady flow calculations.
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Shehadeh, Mhd Ali. "Geometrické řízení hadům podobných robotů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-417115.
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This master’s thesis describes equations of motion for dynamic model of nonholonomic constrained system, namely the trident robotic snakes. The model is studied in the form of Lagrange's equations and D’Alembert’s principle is applied. Actually this thesis is a continuation of the study going at VUT about the simulations of non-holonomic mechanisms, specifically robotic snakes. The kinematics model was well-examined in the work of of Byrtus, Roman and Vechetová, Jana. So here we provide equations of motion and address the motion planning problem regarding dynamics of the trident snake equipped with active joints through basic examples and propose a feedback linearization algorithm.
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Zinszner, Jean-Luc. "Identification des paramètres matériau gouvernant les performances de céramiques à blindage." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0337/document.
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Les céramiques sont couramment utilisées depuis les années 1960 comme matériaux constitutifs de blindages. En effet, grâce à leurs très bonnes propriétés physiques et mécaniques, elles permettent, pour un même niveau de protection, un gain de masse important par rapport aux blindages métalliques. Cependant, la microstructure d’une céramique peut avoir une forte influence sur sa résistance à l’impact. Le but de cette thèse est, à partir d’essais de caractérisation et en se basant sur l’utilisation de quatre nuances de carbure de silicium présentant des microstructures différentes, d’éclaircir les liens entre microstructure et performance à l’impact. Les campagnes expérimentales de compression dynamique et d’écaillage sont basées sur une utilisation innovante du moyen GEPI installé au CEA Gramat. Pour l’étude du comportement en compression dynamique des céramiques, il a permis d’utiliser la technique d’analyse lagrangienne et ainsi de remonter à l’évolution de la résistance des matériaux au cours du chargement. Pour les essais d’écaillage, il a permis, entre autres, une étude de la sensibilité à la vitesse de déformation de la résistance en traction dynamique. La caractérisation de la fragmentation dynamique est quant à elle basée sur des essais d’impact sur la tranche. Un essai innovant d’impact sur céramique préalablement fragmentée a également été dimensionné et réalisé. Ces différents essais expérimentaux ont permis de mettre en évidence et de comprendre l’influence de la microstructure du matériau sur son comportement face aux différents types de sollicitations. L’ensemble des résultats expérimentaux a été comparé à des simulations numériques permettant de valider les lois de comportement utilisées. Le modèle de fragmentation des matériaux fragiles DFH (Denoual-Forquin-Hild) a ainsi montré de très bonnes capacités à simuler le comportement des céramiques sous chargement de traction dynamique (écaillage et fragmentation)Since the sixties, ceramics are commonly used as armour materials. Indeed, thanks to their interesting physical and mechanical properties, they allow a significant weight benefit in comparison to monolithic steel plate armours. However, the microstructure of the ceramic may have a strong influence on its penetration resistance. Based on characterisation tests and on the use of four silicon carbide grades, this work aims to highlight the links between the microstructure and the ballistic efficiency. Experimental compressive and spalling tests are based on the use of the GEPI device. For studying the compressive dynamic behaviour, it allows using the lagrangian analysis method and characterising the yield strength of the material. For studying the tensile dynamic behaviour, it allows assessing the strain-rate sensitivity of the spall strength. An analysis of the fragmentation process is performed based on Edge-On Impact tests. Moreover, an innovating impact test on fragmented ceramics has been designed and performed. The different experimental results allow a better understanding of the influence of the ceramic microstructure on its behaviour under the different loadings. All the experimental data have been compared to numerical results allowing validating the constitutive models. The DFH (Denoual-Forquin-Hild) damage model of brittle materials showed very good capacities to simulate the tensile dynamic behaviour of ceramics (spalling and fragmentation)
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Wadhwani, Rahul. "Physics-based simulation of short-range spotting in wildfires." Thesis, 2019. https://vuir.vu.edu.au/40025/.
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Firebrands play a vital role in the propagation of fire fronts and starting new fires called spotfires ahead of fire fronts during wildfire progression. Firebrands are a harbinger of damage to infrastructure; their effects cause a particularly important threat to people living within the wildland-urban-interface, hampers the suppression of the wildfire or even blocking the evacuation routes for communities and emergency services. Short-range firebrands (<750m) which travel along with the wind with little or no lofting are particularly crucial in increasing the fire front propagation and damaging structures situated closed to wildland-urban interface. In the Daylesford fire of 1962, massive short-range spotting (the process of spot fire ignition and merging of spots caused by firebrands) occurred in eucalyptus forest and increased the rate of fire spread by roughly three times more than the computed using empiricial correlation used by operational fire model. Despite the massive importance of short-range firebrands, little research has been conducted because of the safety risks and challenges of fire to emergency service personnel and to the remote equipment like collection boxes, IR cameras, UAVs, which could be used by researchers to quantify and measure fire properties.
An operational model to represent the transport of short-range firebrand and their likelihood to ignite the surface fuel like forest litter could be developed from a numerical model. This study first attempts to validate a numerical model of firebrand transport with a set of benchmark experiments. The validation of numerical model is carried out using idealised regular shaped firebrand. Fire Dynamic Simulator (FDS) is an open-source Computational Fluid Dynamics (CFD) based fire model which is used in this study. The validation of the numerical model is split into two parts focusing on validation of (1) transport, and (2) ignition potential of firebrands.
Transport of short range firebrands are modelled in FDS using a lagrangian particle sub-model. The model was validated using two firebrand generators (a plastic pipe-based prototype and stainless steel based main firebrand generator) constructed at our facility as a part of this study. The firebrand generator is equipment which generates a repeatable firebrand shower in a confined space. There are few firebrand dragons built around the world. However, our firebrand generators produce a uniform flow field which simplifies the transport of short-range firebrand to be validated. The set of experiments conducted is used to validate the Lagrangian particle model available in FDS used in the transport of short-range firebrands. The validation is carried out on cubiform, cylindrical, and square disc-shaped firebrands. As the default drag model in FDS was not suitable for shapes of firebrands, the drag model is improved to account for a generic shape of firebrand particle. The results show a reasonable agreement with the experiments for all three shapes over a range of particle Reynolds number.
A set of laboratory scale equipment is used to study the ignition likelihood from a short-range firebrand in the numerical model. The boundary fuel vegetation model of FDS is validated. The pyrolysis of vegetation is first tested using thermogravimetric analyser and then with cone calorimeter to estimate mass loss rate, heat-release rate, and time to sustained flaming ignition of three forest litter (pine, eucalyptus, and hay) fuels. Further, a set of thermo-physical properties (thermal conductivity, heat capacity, the heat of pyrolysis, the heat of combustion) of the material tested are also measured using in-house equipment required in the above numerical model. The result showed that the simple linear pyrolysis model is good enough for different forest litter tested with thermogravimetric analyser and cone calorimeter.
Finally, a parametric study of short-range firebrand transport inside an open woodland forest canopy is carried out using the validated Lagrangian particle sub-model. The work focuses on understanding how firebrand distribution varies with a set of variable firebrand characteristics in a wildfire and set a stepping stone for the future study. The results are found to be qualitatively similar to the literature.
Books on the topic "Lagrangian Dynamic Smagorinsky model"
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Koh, Hyun M. A mixed Eulerian-Lagrangian model for the analysis of dynamic fracture. Urbana, IL: University of Illinois at Urbana-Champaign, 1986.
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Cole, Harold L. Monetary and Fiscal Policy through a DSGE Lens. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190076030.001.0001.
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This text is designed to bridge the gap between Ph.D. and undergraduate textbooks in Macroeconomics. The text develops a dynamic stochastic general equilibrium model of money using a cash-in-advance constraint and endogenous production as in the real business cycle literature. The costs of inflation and optimal monetary policy, the impact of labor and capital taxes and as well as optimal fiscal policy are covered. Many extensions, including new Keynesian liquidity shock models are developed. Both standard analytic methods, such as Lagrangian methods, and computational methods using Matlab and Python, are developed as we construct quantitative models.
Book chapters on the topic "Lagrangian Dynamic Smagorinsky model"
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Meneveau, Charles, Fernando Porté-Agel, and Marc B. Parlange. "Accounting for Scale-Dependence in the Dynamic Smagorinsky Model." In Recent Advances in DNS and LES, 317–28. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4513-8_27.
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De Stefano, Giuliano, Daniel E. Goldstein, Oleg V. Vasilyev, and Nicholas K. R. Kevlahan. "Towards Lagrangian dynamic SGS model for SCALES of isotropic turbulence." In Direct and Large-Eddy Simulation VI, 175–82. Dordrecht: Springer Netherlands, 2006. http://dx.doi.org/10.1007/978-1-4020-5152-2_20.
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El Hraiech, Safa, Ajmi Houidi, Zouhaier Affi, and Lotfi Romdhane. "Reduced Inverse Dynamic Model of Parallel Manipulators Based on the Lagrangian Formalism." In Design and Modeling of Mechanical Systems - II, 479–87. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-17527-0_48.
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Azar, Ahmad Taher, Fernando E. Serrano, Nashwa Ahmad Kamal, Anis Koubaa, Adel Ammar, Amjad J. Humaidi, and Ibraheem Kasim Ibraheem. "Lagrangian Dynamic Model Derivation and Energy Shaping Control of Non-holonomic Unmanned Aerial Vehicles." In Proceedings of the International Conference on Artificial Intelligence and Computer Vision (AICV2021), 483–93. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-76346-6_44.
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Thiry, O., G. Winckelmans, and M. Duponcheel. "The Dynamic Smagorinsky Model in $$512^{3}$$ Pseudo-Spectral LES of Decaying Homogeneous Isotropic Turbulence at Very High $$Re_\lambda $$." In Direct and Large-Eddy Simulation XI, 123–28. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-04915-7_17.
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Koo, Bonyoung, and Spyros N. Pandis. "Evaluation of the Equilibrium, Dynamic, and Hybrid Aerosol Modeling Approaches in a One-Dimensional Lagrangian Trajectory Model." In Air Pollution Modelling and Simulation, 289–97. Berlin, Heidelberg: Springer Berlin Heidelberg, 2002. http://dx.doi.org/10.1007/978-3-662-04956-3_28.
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"Challenges for Diadromous Fishes in a Dynamic Global Environment." In Challenges for Diadromous Fishes in a Dynamic Global Environment, edited by Donald J. Jellyman and Melissa M. Bowen. American Fisheries Society, 2009. http://dx.doi.org/10.47886/9781934874080.ch17.
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<em>Abstract</em>.-The location of the spawning grounds of the three species of <em>Anguilla </em>that occur in New Zealand and Australia, shortfin eel <em>A. australis</em>, Australian longfin eel <em>A. dieffenbachii</em>, and Australian longfin eel (also known as speckled longfin eel) <em>A. reinhardtii</em>, are unknown. No larvae of New Zealand longfin eels have been collected, and too few shortfin eel and speckled longfin eel larvae have been collected to use conventional back-tracking of progressively smaller larvae to determine likely spawning areas. The limited larval material together with results from satellite tracking pop-up tags from New Zealand longfin eels indicate that spawning of all three species will be in the tropics, and possible areas were further demarcated by developing a Lagrangian trajectory model based on surface currents derived from hydrography, satellite altimetry, and wind stress. The initial model assumed passive drift of larvae, a third of the total time spent in near-surface layers, and arrival within the larval lifetimes indicated by ages of metamorphosing glass eels. The proportion of successful trajectories enabling arrival offshore of New Zealand or Australia was substantially improved by addition to the model of directed swimming of the larvae towards a destination. The model indicated that possible spawning areas for all three species would be in the northeast of New Caledonia, perhaps within the North Fiji basin between Vanuatu and Fiji. Spawning within this region is consistent with the locations of known larvae, probable migration routes, and the distribution of adult eels in both countries.
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Zou, Dehua, Zhipeng Jiang, Minmin Qiao, Lanlan Liu, Wei Jiang, and Qianwei Yi. "Analysis and Simulation of Dynamic Characteristics for Multi-Split Transmission Line Splicing Pipe Flaw Detection Robot." In Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde220494.
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The splicing pipe is an important hardware on multi-split transmission lines. The quality of its crimping and internal structure directly affects the normal and stable operation of the transmission line. The online flaw detection robot for the splicing pipe is an important means to realize the automatic flaw detection of the splicing pipe. This paper on the basis of proposing a robot mechanism configuration suitable for multi-split transmission line splicing pipe flaw detection, aiming at the matching relationship between the imaging plate movement and the mechanism joint driving torque during the splicing pipe flaw detection process, a flaw detection method is established by using the Lagrangian method. The dynamic model of the operation process of the imaging board is installed, and the relationship between the joint motion of each mechanism and the pose change of the imaging board in the area under the jurisdiction of the four-split wire is analyzed. The displacement and velocity curves of each joint motion of the robot can be obtained. From the simulation results, it can be known that the joint motion of the robot is continuous and stable, and the motion of the imaging plate is driven continuously and smoothly, which realizes the coordinated pose control between the imaging probe and the imaging plate. Coupling pipe flaw detection operation, the research in this paper has important theoretical significance and practical application value for the design of the transmission line joint pipe flaw detection robot system, especially the joint drive mechanism design.
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Liu, Xu, Nan Gui, Mengqi Wu, Takashi Hibiki, Xingtuan Yang, Jiyuan Tu, and Shengyao Jiang. "DEFEM Method and Its Application in Pebble Flows." In Finite Element Method and Its Extensions [Working Title]. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.109347.
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Based on the concept of embedded discrete elements (EDEs), the discrete element-embedded finite element model (DEFEM) is extended in this work. The new method can be used to calculate the motion and stress variation of particles. This work discusses its application in granular flow simulation for particle motions with small deformations. The updated Lagrangian finite element method is used to obtain the coupling solution of the internal stress and the overall motion of particles in the DEFEM. The computation of deformation displacement is based on the concepts of displacement decomposition (translational and rotational motions and deformation displacement). The deformation displacement is the difference between particles and template particles [rigid body, using the discrete element method (DEM) to calculate translational and rotational displacements]. It is used to calculate the dynamic stress distribution of particles and the internal force of the node. Therefore, it has a wide scope of application (for example, it can be extended to non-spherical particles). The software validation proves the accuracy of this method. The application of the DEFEM in the accumulation process of particles is given. The motion characteristics and deformation of particles are discussed, and the stress distribution and force chain structure in particle accumulation are obtained.
Conference papers on the topic "Lagrangian Dynamic Smagorinsky model"
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Tran, Steven A., and Onkar Sahni. "Large Eddy Simulation based on the Residual-based Variational Multiscale Method and Lagrangian Dynamic Smagorinsky Model." In 54th AIAA Aerospace Sciences Meeting. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2016. http://dx.doi.org/10.2514/6.2016-0341.
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Bou-Zeid, Elie, Charles Meneveau, and Marc B. Parlange. "Applications of the Lagrangian Dynamic Model in LES of Turbulent Flow Over Surfaces With Heterogeneous Roughness Distributions." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56127.
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We study turbulent flow over surfaces with varying roughness scales, using large eddy simulation (LES). The goal is to use LES results to formulate effective boundary conditions in terms of effective roughness height and blending height, to be used for RANS. The LES are implemented with the dynamic Smagorinsky model based on the Germano identity. However, as is well-known, when this identity is applied locally, it yields a coefficient with unphysically strong fluctuations and averaging is needed for better realism and numerical stability. The traditional approach consists of averaging over homogeneous directions, for example horizontal planes in channel flow. This requirement for homogeneous directions in the flow field and the concomitant inability to handle complex geometries renders the use of this model questionable in studying the effect of surface heterogeneity. Instead, a new version of the Lagrangian dynamic subgrid-scale (SGS) model [1] is implemented. A systematic set of simulations of flow over patches of differing roughness is performed, covering a wide range of patch length scales and surface roughness values. The simulated mean velocity profiles are analyzed to identify the height of the blending layer and used to measure the effective roughness length. Extending ideas introduced by Miyake [2] and Claussen [3], we have proposed a simple expression for effective surface roughness and blending height knowing local surface patch roughness values and their lengths [4]. Results of the model agreed well with the LES results when the heterogeneous surface consisted of patches of equal sizes. The model is tested here for surfaces with patches of different sizes.
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Bou-Zeid, Elie, Charles Meneveau, and Marc B. Parlange. "Comparison of Four Eddy-Viscosity SGS Models in Large-Eddy Simulation of Flows Over Rough Walls." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56126.
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Large Eddy Simulation (LES) has become an increasingly attractive option for turbulence modeling due to the rise in computing power and the improvement in sub-grid scale (SGS) parameterizations. This study tests the improvements in simulations of wall-bounded flows over heterogeneous surfaces attained by the implementation of three improvements in the eddy-viscosity SGS closure: the dynamic model by Germano et al. [1], the Lagrangian model by Meneveau et al. [2], and the scale-dependent approach by Porte´-Agel et al. [3]. The dynamic model consists of using the resolved scales to ‘measure’ the model coefficient during the simulation; therefore, no a-priori knowledge of the coefficient or the flow physics is needed. The traditional dynamic approach averages the coefficient over statistically homogeneous directions to numerically stabilize the simulations. The Lagrangian model relaxes the need for homogeneous directions by averaging the coefficient over pathlines, hence allowing local determination of the coefficient and facilitating applications to complex-geometry flows. The scale-dependent approach uses the dynamic formulation but does not assume that the SGS coefficients are scale-invariant, as is the case in traditional dynamic formulations. The deficiencies of the traditional Smagorinsky model are confirmed. Implementation of a dynamic model treats some of these deficiencies but is found to be under-dissipative close to the wall in high Reynolds number LES that does not resolve the viscous layer. The sensitivity of the model coefficient to the wall roughness is demonstrated thus confirming the need for a local SGS model such as the Lagrangian model used here. Finally, when the Lagrangian-dynamic model is implemented with the scale-dependent formulation, the results improve significantly.
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Mangani, Luca, David Roos Launchbury, Ernesto Casartelli, and Giulio Romanelli. "Development of High Order LES Solver for Heat Transfer Applications Based on the Open Source OpenFOAM Framework." In ASME Turbo Expo 2015: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/gt2015-43279.
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The computation of heat transfer phenomena in gas turbines plays a key role in the continuous quest to increase performance and life of both component and machine. In order to assess different cooling approaches computational fluid dynamics (CFD) is a fundamental tool. Until now the task has often been carried out with RANS simulations, mainly due to the relatively short computational time. The clear drawback of this approach is in terms of accuracy, especially in those situations where averaged turbulence-structures are not able to capture the flow physics, thus under or overestimating the local heat transfer. The present work shows the development of a new explicit high-order incompressible solver for time-dependent flows based on the open source C++ Toolbox OpenFOAM framework. As such, the solver is enabled to compute the spatially filtered Navier-Stokes equations applied in large eddy simulations for incompressible flows. An overview of the development methods is provided, presenting numerical and algorithmic details. The solver is verified using the method of manufactured solutions, and a series of numerical experiments is performed to show third-order accuracy in time and low temporal error levels. Typical cooling devices in turbomachinery applications are then investigated, such as the flow over a turbulator geometry involving heated walls and a film cooling application. The performance of various sub-grid-scale models are tested, such as static Smagorinsky, dynamic Lagrangian, dynamic one-equation turbulence models, dynamic Smagorinsky, WALE and sigma-model. Good results were obtained in all cases with variations among the individual models.
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Gharakhani, Adrin. "A Grid-Free Method for LES of Incompressible Flow." In ASME 2002 Joint U.S.-European Fluids Engineering Division Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/fedsm2002-31370.
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A grid-free method for the LES of turbulent incompressible flow is presented. The computational engine is based on the Lagrangian Vortex Element Method to account for the dynamics of the resolved vorticity field and the Vorticity Redistribution Method (VRM) to account for turbulent diffusion. Turbulence is modeled here using the standard Smagorinsky subgrid-scale model but work is underway to implement a dynamic version. In this paper, the accuracy and convergence rate of VRM are presented for the case of diffusion with variable viscosity. Furthermore, the adaptivity as well as the robustness of the proposed method in capturing large-scale vortex structures typical of vortex dominated turbulent flow are demonstrated using preliminary results from the LES of the collision of a pair of coaxial vortex rings, perturbed initially by the wave-number of their most unstable mode.
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Rousta, Farid, Bamdad Lessani, and Goodarz Ahmadi. "A Numerical Study on the Effect of Carrier Fluid Subgrid Scales Fluctuations on Deposition and Dispersion of Lagrangian Particles." In ASME 2022 Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/fedsm2022-87651.
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Abstract Large-eddy simulation (LES) coupled with a Lagrangian particle tracking was performed, and the particle deposition and dispersion in turbulent channel flows were investigated. Different test cases with particle Stokes numbers varying from St = 2 to St = 100 were considered in a fully developed turbulent channel flow at a friction Reynolds number of Reτ = 180. The Dynamic Smagorinsky model was used to model the sub-grid scale fluctuations of carrier flow. In the first set of simulations, the effects of sub-grid scale fluctuations in LES were not considered on the Lagrangian particles. Instead, the velocity of carrier flow seen by particles was simply taken as the fluid filtered velocity. Next, direct numerical simulations (DNS) for the same test cases were performed to clarify the importance of sub-grid scale fluctuations seen by the Lagrangian particles. To clarify the differences, the predicted deposition velocities predicted by both LES and DNS methods were compared with the available data in the literature. Deposition velocities predicted by LES were significantly less than those predicted by DNS, especially for the cases with lower particle Stokes numbers. In addition to the deposition velocity, the particle dispersion was also significantly affected by the sub-grid scale fluctuations in the channel. To shed light on differences between particle dispersion for different cases, time and space averaged particle concentrations were evaluated and compared. Finally, the particle mean and fluctuating velocity profiles for different cases were reported.
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Elasrag, Hossam, and Shaoping Li. "Investigation of Extinction and Reignition Events Using the Flamelet Generated Manifold Model." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75420.
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Simulations for the Cambridge swirl bluff-body spray burner are performed near blow-out conditions. A hybrid stress blended eddy simulation (SBES) model is utilized for sub-grid turbulence closure. SBES blends the RANS-SST model at the boundary layer with large eddy simulation dynamic Smagorinsky model outside the boundary layer. The injected N-heptane spray droplets are tracked using a typical Eulerian-Lagrangian approach. Heat transfer coupling between the bluff-body walls and the near-walls fluid is accounted for by coupling the solid and fluid energy equations at the bluff-body surface. Mixing and chemistry are modeled using the Flamelet Generated Manifold (FGM) model. The study investigates how successful the FGM model is in predicting finite rate effects like local extinction and flame lift-off height. To this end, two near blow-out spray flames, the H1S1 (75% to blow-out) and H1S2 (88% to blow-out) are simulated. Good results are shown matching the spray Sauter mean diameter (SMD) and axial velocity mean and rms experimental data. The results also show that the FGM model captured reasonably well the flame structure and lift-off height as well as the spray pattern. Overall the spray droplets mean D32 and mean axial velocity were under-predicted, while the rms distribution matched reasonably well for the H1S1 flame. The mean flame brush lift-off height is estimated based on the statistically stationary mean flame brush and is estimated to be around 6 mm from the bluff-body base. Instantaneous local flame extinction is observed. The H1S2 flame, however, showed similar but slightly better match with the measurements for the mean spray data compared to the H1S1 flame, with slight under-prediction for D32 at Z = 10 mm and Z = 20 mm. Future work will investigate the sensitivity of the simulation to the spray boundary conditions and grid resolution.
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Berland, Julien, Enrico Deri, and André Adobes. "A Numerical Investigation of the Fluidelastic Coupling for a Cell of Flexible Tubes in a Square-in-Line Bundle Subject to Water Cross-Flow." In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45097.
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The unsteady flow motions and the force distribution in a normal square tube array subject to cross-flow induced vibrations are investigated by means of large-eddy simulations. The flow configuration and the operating conditions are taken from the experiments of Gosse et al. (PVP Conference, 2001). The set-up is made of 63 (9 rows and 7 columns) straight tube bundle. The tubes are arranged in a square in line pattern, and a cell of 9 flexible tubes, located in the middle of the bundle, may translate in the drag and lift directions. The LES of cross-flow induced vibrations of a cell of 9 flexible tubes in a normal square tube array is performed. A fully-coupled fluid-structure calculation is hence achieved using Code_Saturne, an open source CFD tool. Turbulence modeling is achieved using the large-eddy simulation framework based on the so-called classical Smagorinsky model. The tube dynamics is modeled by simple mass-spring-damper systems, and the motions of the fluid domain is accounted for by a moving mesh technique (Arbitrary-Lagrangian-Eulerian formulation). The consistency of the calculations is demonstrated by comparing the numerical data to the experiments of Gosse et al. (PVP Conference, 2001) in terms of tube amplitude and flow-induced force spectra, for various gap velocities. Investigation of the spectra of the flow-induced forces then shows that the tube motions ignite the emergence of flow phenomena at constant Strouhal numbers. The fluid-structure interactions are also responsible for the existence of a series of tones at rather constant frequencies, corresponding to the vibrational modes of the flexible cell.
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Yang, Fan, Yulin Wu, and Shuhong Liu. "A Lattice Boltzmann Dynamic Subgrid Model for Lid-Driven Cavity Flow." In ASME 2004 Heat Transfer/Fluids Engineering Summer Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ht-fed2004-56100.
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In recent years, the lattice Boltzmann method (LBM) has developed into an alternative and promising numerical scheme for simulating fluid flows and modeling physics in fluids. In order to proposing lattice Boltzmann method for high Reynolds number fluid flow applications, as well as conforming the value of Smagorinsky coefficient of subgrid model appropriately, a dynamic subgrid turbulence model for lattice Boltzmann method was proposed on the base of dynamic Smagorinsky subgrid model and LBGK model. Then the subgrid LBGK model was used to simulate the two-dimensional driven cavity flow at some high Reynolds numbers. The simulation results including distribution of stream lines, dimensionless velocities distribution, stream function, as well as location of vertex center, were compared with benchmark solution. Both simulation results and benchmark solution are agreed with each other.
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Bogey, Christophe, and Christophe Bailly. "LARGE EDDY SIMULATIONS OF ROUND FREE JETS USING EXPLICIT FILTERING WITH/WITHOUT DYNAMIC SMAGORINSKY MODEL." In Fourth International Symposium on Turbulence and Shear Flow Phenomena. Connecticut: Begellhouse, 2005. http://dx.doi.org/10.1615/tsfp4.1370.
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