Relevant bibliographies by topics / Under-resolved turbulent flow simulations

Academic literature on the topic 'Under-resolved turbulent flow simulations'

Author: Grafiati
Published: 10 December 2022
Last updated: 28 January 2023

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Journal articles on the topic "Under-resolved turbulent flow simulations"

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Grinstein, F. F., A. A. Gowardhan, and J. R. Ristorcelli. "Implicit large eddy simulation of shock-driven material mixing." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 371, no. 2003 (November 28, 2013): 20120217. http://dx.doi.org/10.1098/rsta.2012.0217.

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Under-resolved computer simulations are typically unavoidable in practical turbulent flow applications exhibiting extreme geometrical complexity and a broad range of length and time scales. An important unsettled issue is whether filtered-out and subgrid spatial scales can significantly alter the evolution of resolved larger scales of motion and practical flow integral measures. Predictability issues in implicit large eddy simulation of under-resolved mixing of material scalars driven by under-resolved velocity fields and initial conditions are discussed in the context of shock-driven turbulent mixing. The particular focus is on effects of resolved spectral content and interfacial morphology of initial conditions on transitional and late-time turbulent mixing in the fundamental planar shock-tube configuration.
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Shi, Jingchang, and Hong Yan. "Turbulence amplification in the shock wave/turbulent boundary layer interaction over compression ramp by the flux reconstruction method." Physics of Fluids 35, no. 1 (January 2023): 016122. http://dx.doi.org/10.1063/5.0134222.

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Wall-resolved large eddy simulation on a supersonic turbulent boundary layer over a [Formula: see text] compression ramp is performed under the framework of high order discontinuous methods for a free-stream Mach number [Formula: see text] and Reynolds number [Formula: see text]. The turbulent flow is resolved by the high order flux reconstruction method, and the shock is captured by a high-resolution, but stable weighted essentially non-oscillation limiter. The solver used in this paper is validated by the double Mach reflection case and the Taylor–Green vortex case. The results of shock wave/turbulent boundary layer interaction at the ramp corner are validated by the numerical simulations and the experimental data in the literature. The analysis of the physics behind the turbulence amplification at around the ramp corner is presented. The shear effects and the flow deceleration/acceleration are the main reasons of the turbulence amplification.
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Bryan, George H., Nathan A. Dahl, David S. Nolan, and Richard Rotunno. "An Eddy Injection Method for Large-Eddy Simulations of Tornado-Like Vortices." Monthly Weather Review 145, no. 5 (May 1, 2017): 1937–61. http://dx.doi.org/10.1175/mwr-d-16-0339.1.

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Abstract The structure and intensity of tornado-like vortices are examined using large-eddy simulations (LES) in an idealized framework. The analysis focuses on whether the simulated boundary layer contains resolved turbulent eddies, and whether most of the vertical component of turbulent momentum flux is resolved rather than parameterized. Initial conditions are first generated numerically using a “precursor simulation” with an axisymmetric model. A three-dimensional “baseline” LES is then integrated using these initial conditions plus random perturbations. With this baseline approach, the inner core of the simulated vortex clearly contains resolved turbulent eddies (as expected); however, the boundary layer inflow has very weak resolved turbulent eddies, and the subgrid model accounts for most of the vertical turbulent momentum flux (contrary to the design of these simulations). To overcome this problem, a second precursor simulation is conducted in which resolved turbulent fluctuations develop within a smaller, doubly periodic LES domain. Perturbation flow fields from this precursor LES are then “injected” into the large-domain LES at a specified radius. With this approach, the boundary layer inflow clearly contains resolved turbulent fluctuations, often organized as quasi-2D rolls, which persist into the inner core of the simulation; thus, the simulated tornado-like vortex and its inflowing boundary layer can be characterized as LES. When turbulence is injected, the inner-core vortex structure is always substantially different, the boundary layer inflow is typically deeper, and in most cases the maximum wind speeds are reduced compared to the baseline simulation.
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Konnigk, Lucas, Benjamin Torner, Martin Bruschewski, Sven Grundmann, and Frank-Hendrik Wurm. "Equivalent Scalar Stress Formulation Taking into Account Non-Resolved Turbulent Scales." Cardiovascular Engineering and Technology 12, no. 3 (March 5, 2021): 251–72. http://dx.doi.org/10.1007/s13239-021-00526-x.

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Abstract Purpose Cardiovascular engineering includes flows with fluid-dynamical stresses as a parameter of interest. Mechanical stresses are high-risk factors for blood damage and can be assessed by computational fluid dynamics. By now, it is not described how to calculate an adequate scalar stress out of turbulent flow regimes when the whole share of turbulence is not resolved by the simulation method and how this impacts the stress calculation. Methods We conducted direct numerical simulations (DNS) of test cases (a turbulent channel flow and the FDA nozzle) in order to access all scales of flow movement. After validation of both DNS with literature und experimental data using magnetic resonance imaging, the mechanical stress is calculated as a baseline. Afterwards, same flows are calculated using state-of-the-art turbulence models. The stresses are computed for every result using our definition of an equivalent scalar stress, which includes the influence from respective turbulence model, by using the parameter dissipation. Afterwards, the results are compared with the baseline data. Results The results show a good agreement regarding the computed stress. Even when no turbulence is resolved by the simulation method, the results agree well with DNS data. When the influence of non-resolved motion is neglected in the stress calculation, it is underpredicted in all cases. Conclusion With the used scalar stress formulation, it is possible to include information about the turbulence of the flow into the mechanical stress calculation even when the used simulation method does not resolve any turbulence.
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Fukami, Kai, Koji Fukagata, and Kunihiko Taira. "Super-resolution reconstruction of turbulent flows with machine learning." Journal of Fluid Mechanics 870 (May 7, 2019): 106–20. http://dx.doi.org/10.1017/jfm.2019.238.

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We use machine learning to perform super-resolution analysis of grossly under-resolved turbulent flow field data to reconstruct the high-resolution flow field. Two machine learning models are developed, namely, the convolutional neural network (CNN) and the hybrid downsampled skip-connection/multi-scale (DSC/MS) models. These machine learning models are applied to a two-dimensional cylinder wake as a preliminary test and show remarkable ability to reconstruct laminar flow from low-resolution flow field data. We further assess the performance of these models for two-dimensional homogeneous turbulence. The CNN and DSC/MS models are found to reconstruct turbulent flows from extremely coarse flow field images with remarkable accuracy. For the turbulent flow problem, the machine-leaning-based super-resolution analysis can greatly enhance the spatial resolution with as little as 50 training snapshot data, holding great potential to reveal subgrid-scale physics of complex turbulent flows. With the growing availability of flow field data from high-fidelity simulations and experiments, the present approach motivates the development of effective super-resolution models for a variety of fluid flows.
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ZENG, LANYING, S. BALACHANDAR, PAUL FISCHER, and FADY NAJJAR. "Interactions of a stationary finite-sized particle with wall turbulence." Journal of Fluid Mechanics 594 (December 14, 2007): 271–305. http://dx.doi.org/10.1017/s0022112007009056.

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Reliable information on forces on a finite-sized particle in a turbulent boundary layer is lacking, so workers continue to use standard drag and lift correlations developed for a laminar flow to predict drag and lift forces. Here we consider direct numerical simulations of a turbulent channel flow over an isolated particle of finite size. The size of the particle and its location within the turbulent channel are systematically varied. All relevant length and time scales of turbulence, attached boundary layers on the particle, and particle wake are faithfully resolved, and thus we consider fully resolved direct numerical simulations. The results from the direct numerical simulation are compared with corresponding predictions based on the standard drag relation with and without the inclusion of added-mass and shear-induced lift forces. The influence of turbulent structures, such as streaks, quasi-streamwise vortices and hairpin packets, on particle force is explored. The effect of vortex shedding is also observed to be important for larger particles, whoseReexceeds a threshold.
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Peng, Cheng, Orlando M. Ayala, and Lian-Ping Wang. "A direct numerical investigation of two-way interactions in a particle-laden turbulent channel flow." Journal of Fluid Mechanics 875 (July 26, 2019): 1096–144. http://dx.doi.org/10.1017/jfm.2019.509.

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Understanding the two-way interactions between finite-size solid particles and a wall-bounded turbulent flow is crucial in a variety of natural and engineering applications. Previous experimental measurements and particle-resolved direct numerical simulations revealed some interesting phenomena related to particle distribution and turbulence modulation, but their in-depth analyses are largely missing. In this study, turbulent channel flows laden with neutrally buoyant finite-size spherical particles are simulated using the lattice Boltzmann method. Two particle sizes are considered, with diameters equal to 14.45 and 28.9 wall units. To understand the roles played by the particle rotation, two additional simulations with the same particle sizes but no particle rotation are also presented for comparison. Particles of both sizes are found to form clusters. Under the Stokes lubrication corrections, small particles are found to have a stronger preference to form clusters, and their clusters orientate more in the streamwise direction. As a result, small particles reduce the mean flow velocity less than large particles. Particles are also found to result in a more homogeneous distribution of turbulent kinetic energy (TKE) in the wall-normal direction, as well as a more isotropic distribution of TKE among different spatial directions. To understand these turbulence modulation phenomena, we analyse in detail the total and component-wise volume-averaged budget equations of TKE with the simulation data. This budget analysis reveals several mechanisms through which the particles modulate local and global TKE in the particle-laden turbulent channel flow.
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Ge, Liang, Hwa-Liang Leo, Fotis Sotiropoulos, and Ajit P. Yoganathan. "Flow in a Mechanical Bileaflet Heart Valve at Laminar and Near-Peak Systole Flow Rates: CFD Simulations and Experiments." Journal of Biomechanical Engineering 127, no. 5 (March 31, 2005): 782–97. http://dx.doi.org/10.1115/1.1993665.

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Time-accurate, fully 3D numerical simulations and particle image velocity laboratory experiments are carried out for flow through a fully open bileaflet mechanical heart valve under steady (nonpulsatile) inflow conditions. Flows at two different Reynolds numbers, one in the laminar regime and the other turbulent (near-peak systole flow rate), are investigated. A direct numerical simulation is carried out for the laminar flow case while the turbulent flow is investigated with two different unsteady statistical turbulence modeling approaches, unsteady Reynolds-averaged Navier-Stokes (URANS) and detached-eddy simulation (DES) approach. For both the laminar and turbulent cases the computed mean velocity profiles are in good overall agreement with the measurements. For the turbulent simulations, however, the comparisons with the measurements demonstrate clearly the superiority of the DES approach and underscore its potential as a powerful modeling tool of cardiovascular flows at physiological conditions. The study reveals numerous previously unknown features of the flow.
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Zhou, Bowen, and Fotini Katopodes Chow. "Large-Eddy Simulation of the Stable Boundary Layer with Explicit Filtering and Reconstruction Turbulence Modeling." Journal of the Atmospheric Sciences 68, no. 9 (September 1, 2011): 2142–55. http://dx.doi.org/10.1175/2011jas3693.1.

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Abstract Large-eddy simulation (LES) of the stably stratified atmospheric boundary layer is performed using an explicit filtering and reconstruction approach with a finite difference method. Turbulent stresses are split into the resolvable subfilter-scale and subgrid-scale stresses. The former are recovered from a reconstruction approach, and the latter are represented by a dynamic eddy-viscosity model. The resulting dynamic reconstruction model (DRM) can sustain resolved turbulence with less stringent resolution requirements than conventional closure models, even under strong atmospheric stability. This is achieved by proper representation of subfilter-scale (SFS) backscatter of turbulent kinetic energy (TKE). The flow structure and turbulence statistics for the moderately stable boundary layer (SBL) are analyzed with high-resolution simulations. The DRM simulations show good agreement with established empirical formulations such as flux and gradient-based surface similarity, even at relatively coarse resolution. Similar results can be obtained with traditional closure models at the cost of higher resolution. SBL turbulence under strong stability is also explored. Simulations show an intermittent presence of elevated TKE below the low-level jet. Overall, the explicit filtering and reconstruction approach is advantageous for simulations of the SBL. At coarse resolution, it can extend the working range of LES to stronger stability, while maintaining agreement to similarity theory; at fine resolution, good agreement with theoretical formulations provides confidence in the results and allows for detailed investigation of the flow structure under moderate to strong stability conditions.
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Vita, Giulio, Simone Salvadori, Daniela Anna Misul, and Hassan Hemida. "Effects of Inflow Condition on RANS and LES Predictions of the Flow around a High-Rise Building." Fluids 5, no. 4 (December 7, 2020): 233. http://dx.doi.org/10.3390/fluids5040233.

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An increasing number of engineering applications require accurate predictions of the flow around buildings to guarantee performance and safety. This paper investigates the effects of variations in the turbulent inflow, as predicted in different numerical simulations, on the flow pattern prediction around buildings, compared to wind tunnel tests. Turbulence characteristics were assessed at several locations around a model square high-rise building, namely, above the roof region, at the pedestrian level, and in the wake. Both Reynolds-averaged Navier–Stokes (RANS, where turbulence is fully modelled) equations and large-eddy simulation (LES, where turbulence is partially resolved) were used to model an experimental setup providing validation for the roof region. The performances of both techniques were compared in ability to predict the flow features. It was found that RANS provides reliable results in regions of the flow heavily influenced by the building model, and it is unreliable where the flow is influenced by ambient conditions. In contrast, LES is generally reliable, provided that a suitable turbulent inflow is included in the simulation. RANS also benefits when a turbulent inflow is provided in simulations. In general, LES should be the methodology of choice if engineering applications are involved with the highly separated and turbulent flow features around the building, and RANS provides reliable information when regions of high wind speed and low turbulence are investigated.
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Dissertations / Theses on the topic "Under-resolved turbulent flow simulations"

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Moura, Rodrigo Costa. "On the use of spectral element methods for under-resolved simulations of transitional and turbulent flows." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/55917.

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The present thesis comprises a sequence of studies that investigate the suitability of spectral element methods for model-free under-resolved computations of transitional and turbulent flows. More specifically, the continuous and the discontinuous Galerkin (i.e. CG and DG) methods have their performance assessed for under-resolved direct numerical simulations (uDNS) / implicit large eddy simulations (iLES). In these approaches, the governing equations of fluid motion are solved in unfiltered form, as in a typical direct numerical simulation, but the degrees of freedom employed are insufficient to capture all the turbulent scales. Numerical dissipation introduced by appropriate stabilisation techniques complements molecular viscosity in providing small-scale regularisation at very large Reynolds numbers. Added spectral vanishing viscosity (SVV) is considered for CG, while upwind dissipation is relied upon for DG-based computations. In both cases, the use of polynomial dealiasing strategies is assumed. Focus is given to the so-called eigensolution analysis framework, where numerical dispersion and diffusion errors are appraised in wavenumber/frequency space for simplified model problems, such as the one-dimensional linear advection equation. In the assessment of CG and DG, both temporal and spatial eigenanalyses are considered. While the former assumes periodic boundary conditions and is better suited for temporally evolving problems, the latter considers inflow / outflow type boundaries and should be favoured for spatially developing flows. Despite the simplicity of linear eigensolution analyses, surprisingly useful insights can be obtained from them and verified in actual turbulence problems. In fact, one of the most important contributions of this thesis is to highlight how linear eigenanalysis can be helpful in explaining why and how to use spectral element methods (particularly CG and DG) in uDNS/iLES approaches. Various aspects of solution quality and numerical stability are discussed by connecting observations from eigensolution analyses and under-resolved turbulence computations. First, DG’s temporal eigenanalysis is revisited and a simple criterion named "the 1% rule" is devised to estimate DG’s effective resolution power in spectral space. This criterion is shown to pinpoint the wavenumber beyond which a numerically induced dissipation range appears in the energy spectra of Burgers turbulence simulations in one dimension. Next, the temporal eigenanalysis of CG is discussed with and without SVV. A modified SVV operator based on DG’s upwind dissipation is proposed to enhance CG’s accuracy and robustness for uDNS / iLES. In the sequence, an extensive set of DG computations of the inviscid Taylor-Green vortex model problem is considered. These are used for the validation of the 1% rule in actual three-dimensional transitional / turbulent flows. The performance of various Riemann solvers is also discussed in this infinite Reynolds number scenario, with high quality solutions being achieved. Subsequently, the capabilities of CG for uDNS/iLES are tested through a complex turbulent boundary layer (periodic) test problem. While LES results of this test case are known to require sophisticated modelling and relatively fine grids, high-order CG approaches are shown to deliver surprisingly good quality with significantly less degrees of freedom, even without SVV. Finally, spatial eigenanalyses are conducted for DG and CG. Differences caused by upwinding levels and Riemann solvers are explored in the DG case, while robust SVV design is considered for CG, again by reference to DG’s upwind dissipation. These aspects are then tested in a two-dimensional test problem that mimics spatially developing grid turbulence. In summary, a point is made that uDNS/iLES approaches based on high-order spectral element methods, when properly stabilised, are very powerful tools for the computation of practically all types of transitional and turbulent flows. This capability is argued to stem essentially from their superior resolution power per degree of freedom and the absence of (often restrictive) modelling assumptions. Conscientious usage is however necessary as solution quality and numerical robustness may depend strongly on discretisation variables such as polynomial order, appropriate mesh spacing, Riemann solver, SVV parameters, dealiasing strategy and alternative stabilisation techniques.
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Borse, Manish Rajendra. "Turbulent simulations of feline aortic flow under hypertrophic cardiomyopathy heart condition." Thesis, Mississippi State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10141653.

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A computational fluid dynamics (CFD) model is developed for pulsatile flows and particle transport to evaluate the possible thrombus trajectory in the feline aorta for Hypertrophic Cardiomyopathy (HCM) heart conditions. An iterative target mass flow rate boundary condition is developed, and turbulent simulations with Lagrangian particle transport model are performed using up to 11M grids. The model is validated for human abdominal aorta flow, for which the results agree within 11.6% of the experimental data. The model is applied for flow predictions in a generalized feline aorta for healthy and HCM heart conditions. Results show that in the HCM case, the flow through the iliac arteries decreases by 50%, due to the large recirculation regions in the abdominal aorta compared to the healthy heart case. The flow recirculation also result in stronger vortices with slower decay, causing entrapment of particles in the thoracic aorta and trifurcation regions.

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Ahmad, Imtiaz 1962. "Simulation of turbulent flow and heat transfer under an impinging round jet discharging into a crossflow." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66202.

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Stein, Lewin [Verfasser], Jörn [Akademischer Betreuer] Sesterhenn, Jörn [Gutachter] Sesterhenn, Jan [Gutachter] Delfs, and Peter [Gutachter] Jordan. "Simulation and modeling of a Helmholtz resonator under grazing turbulent flow / Lewin Stein ; Gutachter: Jörn Sesterhenn, Jan Delfs, Peter Jordan ; Betreuer: Jörn Sesterhenn." Berlin : Technische Universität Berlin, 2019. http://d-nb.info/1182423507/34.

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Mouallem, Joseph. "Effects of sub-grid gas turbulence on the meso-scale hydrodynamics of fluidized gas-solid flows." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/18/18147/tde-08112018-170038/.

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Filtered two-fluid models used to perform large scale simulations of gas-solid fluidized flows of industrial risers require closures for filtered parameters such as filtered and residual stresses, and interphase interaction forces mainly effective drag. Closure models for those filtered parameters may be derived by averaging over results of highly resolved simulations with microscopic two-fluid modeling. This work is a contribution in that context. Recent models for filtered parameters have been written as functions of filter size, filtered solid volume fraction, and filtered slip velocity. A recent study showed that macro-scale variables like domain average solid volume fraction and gas Reynolds number also significantly affect the filtered parameters. In the current work, in addition to these filtered and macro-scale variables, the effects of two new variables over the filtered parameters are investigated: filtered solid kinetic energy and sub-grid gas turbulence. It is shown that the filtered solid kinetic energy should be accounted for in the concerning correlations, thereby improving accuracy. Regarding gas turbulence, literature shows it has no significant effects on the motion of high Stokes particles. Extending on literature, this work investigates the sub-grid gas turbulence effects on meso-scale structures formed of high Stokes particles. Results showed that sub-grid gas turbulence has no significant effects on the meso-scale structures and corresponding filtered parameters. The open source code MFIX was used for all simulations. Ranges of dilute concentration of solid and gas Reynolds number typical of riser flow regimes were considered. A modified two-fluid model with microscopic formulation was used. The sub-grid gas turbulence was generated by means of a forcing function procedure which was implemented in the physical space, over the gravitational term of the momentum conservation equation of the gas phase. First, numerical simulations of the gas phase alone were performed, accounting for literature available data, in order to set a turbulent gas field and calibrate the turbulence intensity. Then, the forcing function was introduced in to the two-fluid model and various gas-solid flows were simulated. While the current results show the necessity of accounting for additional variables in the filtered parameter correlation, they also make it clear the necessity of further developments that are required in the search for better accuracy.
Modelos filtrados de dois-fluidos usados em simulações de grandes escalas de escoamentos fluidizados de gás-sólido de risers industriais exigem fechamentos para parâmetros filtrados tais como as tensões filtradas e residuais, e forças interativas interfases, principalmente arrasto efetivo. Modelos de fechamento para estes parâmetros filtrados podem ser gerados a partir de procedimentos de media aplicados sobre resultados de simulações altamente resolvidas com modelagem microscópica de dois-fluidos. Este trabalho é uma contribuição neste contexto. Modelos de fechamento recentes para parâmetros filtrados tem sido formulados em função de tamanho de filtro, fração volumétrica de sólido filtrada, e velocidade de deslizamento filtrada. Estudo recente mostrou que variáveis de macro-escalas como fração volumétrica de sólido e número de Reynolds de gás médios no domínio também afetam significativamente os parâmetros filtrados. No presente trabalho, além dessas variáveis filtradas e de macro-escala, os efeitos de duas novas variáveis sobre os parâmetros filtrados são investigados: energia cinética filtrada do sólido e turbulência submalha do gás. Em relação à energia cinética filtrada do sólido, mostra-se que a sua consideração refina as correlações em questão, contribuindo assim para melhor acuracidade. Com relação à turbulência do gás, a literatura mostra que não tem efeitos significativos no movimento de particulados de elevados números de Stokes. Acrescentando à literatura, este trabalho investiga os efeitos da turbulência sub-malha do gás sobre estruturas de meso-escala formados de particulados de elevados números de Stokes. Os resultados mostraram que a turbulência sub-malha do gás não tem efeitos significativos sobre estruturas de meso-escalas e parâmetros filtrados correspondentes. O código aberto MFIX foi usado para todas as simulações. Faixas de concentração diluída de sólido e número de Reynolds típicos de escoamentos em risers foram considerados. Um modelo modificado de dois fluidos com formulação microscópica foi utilizado. A turbulência sub-malha do gás foi gerada por meio de um procedimento de \'forcing function\' que foi implementado no espaço físico, sobre o termo fonte gravitacional da equação de momentum da fase gás. Primeiramente, simulações numéricas da fase gás foram realizadas separadamente, levando-se em conta dados disponíveis na literatura, a fim de gerar um campo de gás turbulento e calibrar a intensidade de turbulência. Posteriormente, a \'forcing function\' foi introduzida no modelo de dois-fluidos e vários escoamentos de gás-sólido foram simulados. Enquanto os resultados obtidos mostram a necessidade de consideração de variáveis adicionais para correlação de parâmetros filtrados, também deixam claro a necessidade de desenvolvimentos mais aprofundados na busca de melhor acuracidade.
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Wang, Ying. "Numerical study of a confined thermal plume at different flow regimes under the influence of gas radiation." Thesis, La Rochelle, 2020. http://www.theses.fr/2020LAROS005.

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Ce travail est une étude numérique d’un panache thermique confiné en présence de rayonnement de gaz. Le panache est généré par une source de chaleur linéaire immergée dans une cavité cubique remplie d’air. Le but principal est de caractériser l’évolution du panache tout au long de sa transition depuis le régime stationnaire jusqu’à la turbulence, et d’explorer les effets du rayonnement de gaz sur la stabilité, les transferts de chaleur, les champs thermiques et cinétiques du panache.Les simulations numériques DNS sont effectuées pour des nombres de Rayleigh de 106 à 109 avec un logiciel CFD de volumes finis couplé à un module de transferts radiatifs. La situation de convection pure est étudiée en premier lieu pour caractériser les champs thermiques et cinétiques du panache dans différents régimes d’écoulement. Ensuite, le couplage convection-rayonnement est introduit en considérant un gaz gris ou un gaz réel (mélange air – vapeur d’eau). Les effets de l’épaisseur optique sont analysés en détail pour le modèle de gaz gris. Les résultats montrent que le rayonnement stabilise le panache et retarde la transition à l’instationnarité. Le rayonnement homogénéise également le champ thermique et réduit l’extension spatiale du panache. Cependant, l’effet sur le champ cinétique dépend du régime d’écoulement. A l’état stationnaire, le rayonnement de gaz diminue la circulation globale tandis que pour les états transitoires et turbulents, il augmente la dynamique de l’écoulement pour des milieux optiques minces. Ces tendances générales sont confirmées pour le mélange de gaz réel par une étude paramétrique de la concentration de vapeur d’eau et de la température de référence
This work presents a numerical investigation of a confined thermal plume under the influence of gas radiation. Plumeflow is generated by a linear heat source of constant power density immersed in a cubic cavity. The main aim of this thesis is to characterize the evolution of the plume throughout its transition from steady-state to turbulent regime, and to explore the gas radiation effects on flow stability, heat transfers, thermal and kinetic fields of the plume. DNS numerical simulations are performed over a Rayleigh number range from 106 to 109 by applying a finite volume CFD software coupled to a module for radiative heat transfer calculations. The pure convective situation is studied first to characterize the thermal and kinetic fields of the plume in different flow regimes. Next, the convection-radiation coupling is introduced by considering either gray gas or real gas (air - H2O mixture) media. The effects of optical thickness are analyzed in details for gray gas model. Results show that gas radiation stabilizes the plume flow and delays the onset of unsteadiness. Gas radiation also homogenizes the thermal field and reduces its spatial spreading. However, radiation effect on the kinetic field depends on the flow state. For steady state, gas radiation decreases the global flow circulation while for transient and turbulent states, it enhances the flow dynamics in optically thin medium.These general trends of radiation are also confirmed in real gas mixture through a parametric study of water vapor concentration and reference temperature
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Calmet, Hadrien. "Large-scale CFD and micro-particles simulations in a large human airways under sniff condition and drug delivery application." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/670232.

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As we inhale, the air drawn through our nose undergoes successive accelerations and decelerations as it is turned, split, and recombined before splitting again at the end of the trachea as it enters the bronchi. Fully describing the dynamic behaviour of the airflow and how it transports inhaled particles poses a severe challenge to computational simulations. The dynamics of unsteady flow in the human large airways during a rapid and short inhalation (a so-called sniff) is a perfect example of perhaps the most complex and violent human inhalation inflow. Combining the flow solution with a Lagrangian computation reveals the effects of flow behaviour and airway geometry on the deposition of inhaled microparticles. Highly detailed large-scale computational fluid dynamics allow resolving all the spatial and temporal scales of the flow, thanks to the use of massive computational resources. A highly parallel finite element code running on supercomputers can solve the transient incompressible Navier-Stokes equations on unstructured meshes. Given that the finest mesh contained 350 million elements, the study sets a precedent for large-scale simulations of the respiratory system, proposing an analysis strategy for mean flow, fluctuations, wall shear stresses, energy spectral and particle deposition on a rapid and short inhalation. Then in a second time, we will propose a drug delivery study of nasal sprayed particle from commercial product in a human nasal cavity under different inhalation conditions; sniffing, constant flow rate and breath-hold. Particles were introduced into the flow field with initial spray conditions, including spray cone angle, insertion angle, and initial velocity. Since nasal spray atomizer design determines the particle conditions, fifteen particle size distributions were used,each defined by a log-normal distribution with a different volume mean diameter. This thesis indicates the potential of large-scale simulations to further understanding of airway physiological mechanics, which is essential to guide clinical diagnosis; better understanding of the flow and delivery of therapeutic aerosols, which could be applied to improve diagnosis and treatment.
En una inhalación, el aire que atraviesa nuestra cavidad nasal es sometido a una serie de aceleraciones y deceleraciones al producirse un giros, bifurcaciones y recombinarse de nuevo antes de volver a dividirse de nuevo a la altura de la tráquea en la entrada a los bronquios principales. La descripción precisa y acurada del comportamiento dinámico de este fluido así como el transporte de partículas inhalada que entran con el mismo a través de una simulación computacional supone un gran desafío. La dinámica del fluido en las vías respiratorias durante una inhalación rápida y corta (también llamado sniff) es un ejemplo perfecto de lo que sería probablemente la inhalación en el ser humano más compleja y violenta. Combinando la solución del fluido con un modelo lagrangiano revela el comportamiento del flujo y el effecto de la geometría de las vías respiratorias sobre la deposición de micropartículas inhaladas. La dinámica de fluidos computacional a gran escala de alta precisión permite resolver todas las escalas espaciales y temporales gracias al uso de recursos computacionales masivos. Un código de elementos finitos paralelos que se ejecuta en supercomputadoras puede resolver las ecuaciones transitorias e incompresibles de Navier-Stokes. Considerando que la malla más fina contiene 350 millones de elementos, cabe señalar que el presente estudio establece un precedente para simulaciones a gran escala de las vías respiratorias, proponiendo una estrategia de análisis para flujo medio, fluctuaciones, tensiones de corte de pared, espectro de energía y deposición de partículas en el contexto de una inhalación rápida y corta. Una vez realizado el analisis anterior, propondremos un estudio de administración de fármacos con un spray nasal en una cavidad nasal humana bajo diferentes condiciones de inhalación; sniff, caudal constante y respiración sostenida. Las partículas se introdujeron en el fluido con condiciones iniciales de pulverización, incluido el ángulo del cono de pulverización, el ángulo de inserción y la velocidad inicial. El diseño del atomizador del spray nasal determina las condiciones de partículas, entonces se utilizaron quince distribuciones de tamaño de partícula, cada uno definido por una distribución logarítmica normal con una media de volumen diferente. Esta tesis demuestra el potencial de las simulaciones a gran escala para una mejor comprensión de los mecanismos fisiológicos de las vías respiratorias. Gracias a estas herramientas se podrá mejorar el diagnóstico y sus respectivos tratamientos ya que con ellas se profundizará en la comprensión del flujo que recorre las vías aereas así como el transporte de aerosoles terapéuticos.
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8

Gai, Guodong. "Modeling of water sprays effects on premixed hydrogen-air explosion, turbulence and shock waves Modeling pressure loads during a premixed hydrogen combustion in the presence of water spray Numerical study on laminar flame velocity of hydrogen-air combustion under water spray effects Modeling of particle cloud dispersion in compressible gas flows with shock waves A new formulation of a spray dispersion model for particle/droplet-laden flows subjected to shock waves Particles-induced turbulence: a critical review of physical concepts, numerical modelings and experimental investigation A new methodology for modeling turbulence induced 1 by a particle-laden flow using a mechanistic model." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMIR14.

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Cette thèse de doctorat est dédiée au développement de modèles physiques pour l’étude des systèmes d’aspersion de gouttelettes d’eau en milieu réactif d’hydrogène-air pré-mélangée dans les centrales nucléaires. Des modèles d’ordre réduit sont développés pour décrire l’évaporation des gouttelettes d’eau dans la flamme, la dispersion des nuages de particules après le passage des ondes de choc et l’évolution de l’échelle caractéristiques de turbulence avec la présence d’un jet d’eau. Une nouvelle méthodologie est proposée pour évaluer les effets de l’évaporation par l’aspersion sur la propagation de la flamme d’hydrogène turbulente à l’intérieur d’un volume fermé et un modèle simple est développé pour la quantification de la décélération de la vitesse laminaire avec l’évaporation des gouttelettes à l’intérieur de la flamme. Également, un modèle analytique est proposé pour la prédiction de la dispersion de nuage de particule après le passage d’une onde de choc en s’appuyant sur le one-way formalisme avec une extension afin de prédire l’apparition d’un pic de densité du nombre de particules en utilisant le two-way formalisme. En ce qui concerne la modulation de la turbulence induite par les particules, un modèle simple est utilisé pour l’estimation des échelles intégrales de la turbulence induites par l’injection de nuage des particules. Ces modèles numériques développés peuvent être couplés pour être mis en œuvre dans les simulations numériques à grande échelle de l’effet du système d’aspersion sur les explosions accidentelles d’hydrogène dans les centrales nucléaires
This PhD dissertation is dedicated to develop simple models to investigate the effect of water spray system on the premixed hydrogen-air combustion in the nuclear power plants. Specific simple models are developed to describe the water droplet evaporation in the flame, particle cloud dispersion after the shock wave passage, and turbulence length scale evolution with the presence of a water spray. A methodology is proposed to evaluate the spray evaporation effects on the propagation of the turbulent hydrogen flame inside a closed volume and a simple model is developed for the quantification of the laminar velocity deceleration with the droplets evaporation inside the flame. An analytical model is proposed for the prediction of particle cloud dispersion after the shock passage in the one-way formalism and another analytical model is dedicated to describe the spray-shock interaction mechanism and predict the appearance of a particle number density peak using the two-way formalism. A review of the important criteria and physical modelings related to the particle-induced turbulence modulation is given and a mechanistic model is used for the estimation of the turbulent integral length scales induced by the injection of particle clouds. These developed numerical models can be coupled to implement in the large-scale numerical simulations of the spray system effects on the accidental hydrogen explosions in the nuclear power plants
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Chrigui, Mouldi. "Eulerian-Lagrangian Approach for Modeling and Simulations of Turbulent Reactive Multi-Phase Flows under Gas Turbine Combustor Conditions." Phd thesis, 2005. http://tuprints.ulb.tu-darmstadt.de/635/1/Disseration_Mouldi-Chrigui.pdf.

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The work presented in this thesis resulted in the development and application of different mathematical sub-models to describe the physics of turbulent reacting spray typical for gas turbine combustors. The resulting complete models were formulated in the Eulerian-Lagrangian context. Emphases were primarily put on the interaction between solid particles and turbulence seeking a correct prediction of turbulent quantities in turbulent two phase flows. The investigation of the feedback mechanism of particles on the continuous phase within the turbulent two-phase flow which is known as turbulence modulation was carried out with three different modulation models. Computations reveal that the obtained results of the turbulent kinetic energy using the thermodynamically consistent model, reproduce well both the turbulence attenuation and production. Indeed, the standard model underestimates the turbulence. This model is dissipative for small and big particles, whereas the model by Crowe is overall productive. Two evaporation models have been developed, integrated in FASTEST/LAG3D code and subsequently applied. The computations were achieved using a fully two-way coupling process. A systematical study of the interaction processes including turbulence, turbulence modulation, mass and heat transfer has been satisfactory carried out. Simulations showed that non equilibrium model agree most favorably with experimental measurements of the droplet mass flux. In order to characterize the turbulence-droplet vaporization interaction regimes, a vaporization Damkoehler number (Dav) has been introduced. Numerical results have demonstrated that in case of Dav>1 turbulence augmentation enhances the evaporation rate, whereas for Dav¡Ü1 the opposite phenomenon takes place, namely the rate of evaporation is reduced. The spray combustion was studied in a complex industrial configuration, which consists of a single annular combustor that was experimentally measured by Rolls-Royce Deutschland. Simulations were performed using k-eps as well as Reynolds Stress model (Jones Musonge) for turbulence, an assumed shape of probability density function to prescribe turbulence combustion interaction and different models describing the turbulence modulation. Equilibrium and a flamelet chemistry approaches were used. Results showed that predicted RTDF distributions are satisfactory and provide plausible results compared with measurements. The use of the thermodynamically consistent modulation model allows an acceptable behavior of the temperature distribution compared to the standard modulation model. On the other hand, both evaporation models (equilibrium and non-equilibrium) provided similar results for the temperature distribution. Numerical computations including the flamelet turbulent combustion model predicted a lower peak reaction temperature and a more gradual temperature decrease than predictions using equilibrium chemistry. As final conclusion one can reiterate that the combination of the following sub-models: thermodynamically consistent model for the turbulence modulation, Langmuir-Knudsen non-equilibrium model for the evaporation, Reynolds Stress Model for the turbulence and flamelet model for the chemistry establish a reliable complete model that seems to allows a better description of reactive multi-phase flow studied in the frame of this work.
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"Investigation of Transition and Vortex Systems of a Dynamically Pitching Airfoil Under the Free-stream Turbulence Conditions." Master's thesis, 2017. http://hdl.handle.net/2286/R.I.45526.

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abstract: The effect of reduced frequency on dynamic stall behavior of a pitching NACA0012 airfoil in a turbulent wake using Direct Numerical Simulations is presented in the current study. Upstream turbulence with dynamically oscillating blades and airfoils is associated with ambient flow unsteadiness and is encountered in many operating conditions. Wake turbulence, a more realistic scenario for airfoils in operation, is generated using a small solid cylinder placed upstream, the vortices shed from which interact with the pitching airfoil affecting dynamic stall behavior. A recently developed moving overlapping grid approach is used using a high-order Spectral Element Method (SEM) for spatial discretization combined with a dynamic time-stepping procedure allowing for up to third order temporal discretization. Two cases of reduced frequency (k = 0:16 and 0:25) for airfoil oscillation are investigated and the change in dynamic stall behavior with change in reduced frequency is studied and documented using flow-fields and aerodynamic coefficients (Drag, Lift and Pitching Moment) with a focus on understanding vortex system dynamics (including formation of secondary vortices) for different reduced frequencies and it’s affect on airfoil aerodynamic characteristics and fatigue life. Transition of the flow over the surface of an airfoil for both undisturbed and disturbed flow cases will also be discussed using Pressure coefficient and Skin Friction coefficient data for a given cycle combined with a wavelet analysis using Morse wavelets in MATLAB.
Dissertation/Thesis
Masters Thesis Mechanical Engineering 2017
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Books on the topic "Under-resolved turbulent flow simulations"

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Succi, Sauro. Lattice Boltzmann for Turbulence Modeling. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199592357.003.0024.

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This chapter introduces the main ideas behind the application of LBE methods to the problem of turbulence modeling, namely the simulation of flows which contain scales of motion too small to be resolved on present-day and foreseeable future computers. Many real-life flows of practical interest exhibit Reynolds numbers far too high to be directly simulated in full resolution on present-day computers and arguably for many years to come. This raises the challenge of predicting the behavior of highly turbulent flows without directly simulating all scales of motion which take part to turbulence dynamics, but only those that fall within the computer resolution at hand.
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Succi, Sauro. Lattice Boltzmann for Turbulent Flows. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780199592357.003.0020.

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This chapter presents the main ideas behind the application of LB methods to the simulation of turbulent flows. The attention is restricted to the case of direct numerical simulation, in which all scales of motion within the grid resolution are retained in the simulation. Turbulence modeling, in which the effect of unresolved scales on the resolved ones is taken into account by various forms of modeling, will be treated in a subsequent chapter.
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P, Givi, and United States. National Aeronautics and Space Administration., eds. Large eddy simulations and direct numerical simulations of high speed turbulent reacting flows: Progress report on activities supported under grant NAG 1-1122 for the period February 1, 1993 - October 31, 1993. [Buffalo, N.Y.]: Turbulence Research Laboratory, School of Engineering and Applied Sciences, State University of New York at Buffalo, 1993.

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4

Peyman, Givi, and United States. National Aeronautics and Space Administration., eds. Large eddy simulations and direct numerical simulations of high speed turbulent reacting flows: Semiannual report submitted to NASA Langley Research Center : summary of activities supported under grant NAG 1-1122 for the period May 1, 1991 - October 31, 1991. [Washington, DC: National Aeronautics and Space Administration, 1991.

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P, Givi, and United States. National Aeronautics and Space Administration., eds. Large eddy simulations and direct numerical simulations of high speed turbulent reacting flows: Semi-annual report submitted to NASA Langley Research Center : summary of activities supported under grant NAG 1-1122 for the period August 1, 1992 - January 31, 1993. [Buffalo, N.Y.]: Turblence Research Laboratory, School of Engineering and Applied Sciences, State University of New York at Buffao, 1993.

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6

A, Jaberi F., and United States. National Aeronautics and Space Administration., eds. Numerical simulation of high-speed turbulent reacting flows: Annual report submitted to the NASA Langley Research Center, progress report on activities supported under grant NAG 1-1122 for the period August 1, 1996 - July 31, 1997. [Washington, DC: National Aeronautics and Space Administration, 1996.

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7

A, Jaberi F., and United States. National Aeronautics and Space Administration., eds. Numerical simulation of high-speed turbulent reacting flows: Annual report submitted to the NASA Langley Research Center, progress report on activities supported under grant NAG 1-1122 for the period August 1, 1996 - July 31, 1997. [Washington, DC: National Aeronautics and Space Administration, 1996.

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Book chapters on the topic "Under-resolved turbulent flow simulations"

1

Kaller, Thomas, Alexander Doehring, Stefan Hickel, Steffen J. Schmidt, and Nikolaus A. Adams. "Assessment of RANS Turbulence Models for Straight Cooling Ducts: Secondary Flow and Strong Property Variation Effects." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 309–21. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53847-7_20.

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Abstract We present well-resolved RANS simulations of two generic asymmetrically heated cooling channel configurations, a high aspect ratio cooling duct operated with liquid water at $$Re_b = 110 \times 10^3$$ and a cryogenic transcritical channel operated with methane at $$Re_b = 16 \times 10^3$$. The former setup serves to investigate the interaction of turbulence-induced secondary flow and heat transfer, and the latter to investigate the influence of strong non-linear thermodynamic property variations in the vicinity of the critical point on the flow field and heat transfer. To assess the accuracy of the RANS simulations for both setups, well-resolved implicit LES simulations using the adaptive local deconvolution method as subgrid-scale turbulence model serve as comparison databases. The investigation focuses on the prediction capabilities of RANS turbulence models for the flow as well as the temperature field and turbulent heat transfer with a special focus on the turbulent heat flux closure influence.
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Gehrke, Martin, Amir Banari, and Thomas Rung. "Performance of Under-Resolved, Model-Free LBM Simulations in Turbulent Shear Flows." In Progress in Hybrid RANS-LES Modelling, 3–18. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-27607-2_1.

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Loosen, Simon, Matthias Meinke, and Wolfgang Schröder. "Numerical Analysis of the Turbulent Wake for a Generic Space Launcher with a Dual-Bell Nozzle." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 163–77. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-53847-7_10.

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Abstract The turbulent wake of an axisymmetric generic space launcher equipped with a dual-bell nozzle is simulated at transonic ($$Ma_\infty = 0.8$$ and $$Re_D = 4.3\cdot 10^5$$) and supersonic ($$Ma_\infty = 3$$ and $$Re_D = 1.2\cdot 10^6$$) freestream conditions, to investigate the influence of the dual-bell nozzle jet onto the wake flow and vice versa. In addition, flow control by means of four in circumferential direction equally distributed jets injecting air encountering the backflow in the recirculation region is utilized to determine if the coherence of the wake and consequently, the buffet loads can be reduced by flow control. The simulations are performed using a zonal RANS/LES approach. The time-resolved flow field data are analyzed by classical spectral analysis, two-point correlation analysis, and dynamic mode decomposition (DMD). At supersonic freestream conditions, the nozzle counter pressure is reduced by the expansion of the outer flow around the nozzle lip leading to a decreased transition nozzle pressure ratio. In the transonic configuration a spatio-temporal mode with an eigenvalue matching the characteristic buffet frequency of $$Sr_D=0.2$$ is extracted by the spectral and DMD analysis. The spatial shape of the detected mode describes an antisymmetric wave-like undulating motion of the shear layer inducing the low frequency dynamic buffet loads. By flow control this antisymmetric coherent motion is weakened leading to a reduction of the buffet loads on the nozzle fairing.
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Coleman, G. N., and N. N. Mansour. "Simulation and Modeling of Homogeneous Compressible Turbulence Under Isotropic Mean Compression." In Turbulent Shear Flows 8, 269–82. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-77674-8_19.

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Vincent, Stéphane, Jean-Luc Estivalézes, and Ruben Scardovelli. "Large Eddy Simulation of Resolved Scale Interfacial Flows." In Small Scale Modeling and Simulation of Incompressible Turbulent Multi-Phase Flow, 189–217. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-09265-7_7.

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Bassi, F., A. Colombo, A. Crivellini, M. Franciolini, A. Ghidoni, G. Manzinali, and G. Noventa. "Under-Resolved Simulation of Turbulent Flows Using a p-adaptive Discontinuous Galerkin Method." In Springer Proceedings in Physics, 157–62. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-22196-6_25.

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Chu, Xu, Johannes Müller, and Bernhard Weigand. "Interface-Resolved Direct Numerical Simulation of Turbulent Flow over Porous Media." In High Performance Computing in Science and Engineering '19, 343–54. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-66792-4_23.

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Vincent, Stéphane, Jean-Luc Estivalézes, and Ruben Scardovelli. "DNS of Resolved Scale Interfacial and Free Surface Flows with Fictitious Domains." In Small Scale Modeling and Simulation of Incompressible Turbulent Multi-Phase Flow, 7–49. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-09265-7_2.

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Kuetemeier, Dennis, and Amsini Sadiki. "Modeling and Simulation of a Turbulent Multi-component Two-phase Flow Involving Phase Change Processes Under Supercritical Conditions." In Fluid Mechanics and Its Applications, 189–209. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-09008-0_10.

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AbstractThe present paper aims at developing a generally valid, consistent numerical description of a turbulent multi-component two-phase flow that experiences processes that may occur under both subcritical and trans-critical or supercritical operating conditions. Within an appropriate LES methodology, focus is put on an Euler-Eulerian method that includes multi-component mixture properties along with phase change process. Thereby, the two-phase flow fluid is considered as multi-component mixtures in which the real fluid properties are accounted for by a composite Peng-Robinson (PR) equation of state (EoS), so that each phase is governed by its own PR EoS. The suggested numerical modelling approach is validated while simulating the disintegration of an elliptic jet of supercritical fluoroketone injected into a helium environment. Qualitative and quantitative analyses are carried out. The results show significant coupled effect of the turbulence and the thermodynamic on the jet disintegration along with the mixing processes. Especially, comparisons between the numerical predictions and available experimental data provided in terms of penetration length, fluoroketone density, and jet spreading angle outline good agreements that attest the performance of the proposed model at elevated pressures and temperatures. Further aspects of transcritical jet flow case as well as comparison with an Eulerian-Lagrangian approach which is extended to integrate the arising effects of vanishing surface tension in evolving sprays are left for future work.
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Stein, Lewin, Julius Reiss, and Jörn Sesterhenn. "Numerical Simulation of a Resonant Cavity: Acoustical Response Under Grazing Turbulent Flow." In Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 671–81. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-64519-3_60.

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Conference papers on the topic "Under-resolved turbulent flow simulations"

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Burton, Tristan M., and John K. Eaton. "Fully Resolved Simulations of Stationary Particles in Turbulent Flow." In ASME/JSME 2003 4th Joint Fluids Summer Engineering Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/fedsm2003-45721.

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Gas flows containing a dilute loading of solid particle constitute an important class of multiphase flows. In most cases the gas flow is turbulent, and the interactions between the particles and the turbulence offer major modeling challenges. Many numerical models implicitly assume that the particles are significantly smaller than all turbulence length scales. Simple particle drag laws derived for uniform steady flow around a sphere are used to compute the motion of point-particles, and to determine the magnitude of the point-forces that are applied to the gas phase in order to produce turbulence modification. This technique may be appropriate if the particle is small relative to any turbulent eddies, but in many practical problems the particle diameter, d, is of the same order as the flow Kolmogorov scale, η. Here we perform fully-resolved simulations of a fixed particle in decaying homogeneous isotropic turbulence using an overset grid method. All flow scales are accurately resolved with this technique including the effect of the no-slip boundary condition at the particle surface. A set of 29 simulations with an initial Taylor microscale Reynolds number, Reλ = 32.2, and Kolmogorov length scale, η = 0.45d are computed to obtain a useful statistical sample. The turbulent kinetic energy and viscous dissipation near the particle surface in laden and unladen simulations are compared to provide understanding of the turbulence modification process. We anticipate that these results will provide direction for the development of turbulence modification models suitable for larger scale simulations where the flow cannot be resolved to the particle surface.
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Xun, Qian-Qiu, Bing-Chen Wang, and Gang Yan. "Transport of Resolved Turbulent Stresses in a Spanwise Rotating Channel Flow." In ASME 2010 3rd Joint US-European Fluids Engineering Summer Meeting collocated with 8th International Conference on Nanochannels, Microchannels, and Minichannels. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-30518.

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In this paper, we investigate the transport of resolved turbulent stresses in a plane channel flow subjected to spanwise rotation using the method of large-eddy simulation (LES). We present both the general and simplified transport equations for the resolved turbulent stresses, which are essential for understanding the unique pattern of turbulent kinetic energy production in a rotating system. Numerical simulations are performed using a dynamic nonlinear model (DNM) for closure of the filtered momentum equation. The turbulent flow field studied in this research is characterized by a Reynolds number Reτ = 150 and various rotation numbers Roτ ranging from 0 to 7.5. In order to validate the LES approach, turbulent statistics obtained from the simulations are thoroughly compared with the available experimental and direct numerical simulation results.
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3

Haidl, J., Z. Chára, and V. Matoušek. "Experimental Validation of Granular Flow Kinetic Theory Under Turbulent Flow Conditions." In Topical Problems of Fluid Mechanics 2022. Institute of Thermomechanics of the Czech Academy of Sciences, 2022. http://dx.doi.org/10.14311/tpfm.2022.011.

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The mixed classical and extended kinetic theory of granular flows is used for modeling the characteristics of particles-water turbulent sheet flow. The open-source solver sedFoam v3.1 is used for the 1-D and 2-D flow simulations. The simulation results are compared to the experimental data measured in the open channel. After that, the simulation parameters are optimized to achieve the best possible agreement between the simulation and the experimental results. The unsatisfactory performance of the KT models and the observed simulation instabilities are discussed.
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4

Ma, Peter C., Xiang Yang, and Matthias Ihme. "Direct numerical simulations of turbulent channel flow under transcritical conditions." In 2018 AIAA Aerospace Sciences Meeting. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2018. http://dx.doi.org/10.2514/6.2018-0582.

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Zhang, Xu, Dan Stanescu, and Jonathan W. Naughton. "Development of a Spectral Element DNS/LES Method for Turbulent Flow Simulations." In ASME/JSME 2007 5th Joint Fluids Engineering Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/fedsm2007-37443.

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This paper describes a turbulent flow simulation method, which is based on combination of spectral element and large eddy simulation (LES) technique. The robust, high-order discontinuous Galerkin (DG) spectral element method for large-eddy simulation of compressible flows allows for arbitrary order of accuracy and has excellent stability properties. A local spectral discretization in terms of Legendre polynomials is used on each element of the (possibly unstructured) mesh, which allows for high-accurate simulations of turbulent flows. Discontinuities across the interfaces of the elements are resolved using a Riemann solver. An isoparametric representation of the geometry is implemented, with boundaries of the domain discretized to the same order of accuracy as the solution, and explicit low-storage Runge-Kutta methods are used for time integration. Large eddy simulation has proven to be a valuable technique for the calculation of turbulent flows. An element based filtering technique is used in conjunction with the standard Smagorinsky eddy viscosity model to estimate the effect of sub-grid scales stresses in this paper. The recently developed nonlinear model [1] will also be added in the future. The final aim of this project is to use the LES methodology in swirling jet flow simulation. As a first step towards these simulations, simulations of compressible turbulent mixing layer and back-facing step are also performed to evaluate the robust method. Initial results based on both DNS and large eddy simulations are presented in this paper. Future work will be to validate the code.
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Brazell, Michael J., and Dimitri J. Mavriplis. "High-Order Discontinuous Galerkin Mesh Resolved Turbulent Flow Simulations of a NACA 0012 Airfoil (Invited)." In 53rd AIAA Aerospace Sciences Meeting. Reston, Virginia: American Institute of Aeronautics and Astronautics, 2015. http://dx.doi.org/10.2514/6.2015-1529.

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Bhushan, S., M. Elmellouki, W. D. Jock, D. K. Walters, J. K. Lai, Y. A. Hassan, A. Obabko, and E. Merzari. "Numerical Investigation of Flow and Heat Transfer Characteristics for Attached and Separated Low-Pr Flows." In ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/ajkfluids2019-5273.

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Abstract This study performs a comprehensive analysis of the effect of flow separation and reattachment, convective conditions and Pr to understand their effect on heat transfer characteristics and the predictive capability of low- and hig-fidelity turbulence models are assessed. To achieve the objective DNS is performed for plane channel flow at Reτ = 640, Pr = 0.71 and 0.025 involving mixed forced and natural convection condition, and RANS, hybrid RANS/LES, and LES calculations are performed for backward backing step with expansion ratio 1.5, Pr = 0.71 and 0.0088 and Ri = 0 and 0.338. Channel flow simulations reveal that the convective conditions affect the near-wall turbulent structures and thermal diffusion more significantly in high-Re flows that in low-Re flows. Thus, the generated DNS database provides a challenging test case for turbulence model validation. For backward facing step case, all the turbulence models predict the overall flow characteristics, and Ri = 0 case is a more challenging validation test case than Ri = 0.338, as the former involves complex turbulent diffusion, whereas the latter is dominated by large scale buoyancy driven convection. Results show that well resolved PANS and LES predictions can help in improve understanding of turbulent diffusion under complex convection and flow separation/ reattachment regimes. RANS results are also quite encouraging and indicates that they may represent a reasonable compromise between computational expense and accuracy for cases in which high resolution simulations are not feasible.
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8

Bergant, R., and I. Tiselj. "Numerical Simulations of Turbulent Flume Heat Transfer at Pr = 5.4: Impact of the Smallest Temperature Scales." In ASME 2005 Fluids Engineering Division Summer Meeting. ASMEDC, 2005. http://dx.doi.org/10.1115/fedsm2005-77144.

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In the present paper a role of the smallest diffusive scales of a passive scalar field in the near-wall turbulent flow was examined with pseudo-spectral numerical simulations. Temperature fields were analyzed at friction Reynolds number Reτ = 170.8 and at Prandtl number, Pr = 5.4. Results of direct numerical simulation (DNS) were compared with the under-resolved simulation where the velocity field was still resolved with the DNS accuracy, while a coarser grid was used to describe the temperature field. Since the smallest temperature scales remained unresolved in this simulation, an appropriate spectral turbulent thermal diffusivity was applied to avoid pileup at higher wave numbers. In spite of coarser numerical grid, the temperature field is still highly correlated with the DNS results, and thus point to practically negligible role of the diffusive temperature scales on the macroscopic behavior of the turbulent heat transfer.
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Xia, Yu, Phil Stopford, Patrick Sharkey, and Ishan Verma. "Dynamic Mesh Adaption for Scale-Resolving Reacting Flow Simulations." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-59100.

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Abstract In this paper, a dynamic adaptive mesh refinement method is used in conjunction with a hybrid scale-resolving turbulence model to solve industrial combustion problems. The objective of the adaption method is to track and resolve characteristic turbulent structures arising from swirlers, pilot injectors and flame propagation in industrial burner configurations. By employing Polyhedral Unstructured Mesh Adaption (PUMA)® within Ansys Fluent® solver, local regions of mesh are refined to capture gradients in temperature, velocity and other key variables. For Scale-Resolving Simulations (SRS), highly refined meshes are required to resolve a sufficient range of turbulent scales. In this work, a strategy is proposed to evaluate the scale-resolving quality of the mesh and to refine it dynamically in a transient simulation. The condition used for adapting the mesh is based on the gradients of key variables such as temperature and velocity, whilst the large-scale eddies are resolved using an approach based on the LES mesh resolution index. This strategy is then applied to a series of test cases (a diffusion jet flame, a bluff-body premixed flame and a swirl stabilized flame), using the hybrid Stress-Blended Eddy Simulation (SBES) turbulence model and a Flamelet Generated Manifold (FGM) combustion model. The numerical results are compared with available experimental data, and the accuracy of the solutions is discussed.
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DeLeon, Rey, and Inanc Senocak. "A Novel Fix to Reduce the Log-Layer Mismatch in Wall-Modeled Large-Eddy Simulations of Turbulent Channel Flow." In ASME 2016 Fluids Engineering Division Summer Meeting collocated with the ASME 2016 Heat Transfer Summer Conference and the ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/fedsm2016-7698.

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The log-layer mismatch arises when a Reynolds-averaged Navier-Stokes (RANS) model is blended with a large-eddy simulation (LES) model in a hybrid fashion. Numerous researchers have tackled this problem by simulating a turbulent channel flow. We show that the log-layer mismatch in hybrid RANS-LES can be reduced substantially by splitting the mean pressure gradient term in the wall-normal direction in a manner that keeps the mass flow rate constant. Additionally, an analysis of the wall-normal variation of the friction velocity shows a constant value is recovered in the resolved LES region different than the value at the wall. Second-order turbulence statistics agree very well with direct numerical simulation (DNS) benchmarks when scaled with the friction velocity extracted from the resolved LES region. In light of our findings, we suggest that the current convention to drive a turbulent periodic channel flow with a uniform mean pressure gradient be revisited in testing eddy-viscosity-based hybrid RANS-LES models as it appears to be the culprit behind the log-layer mismatch.
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Reports on the topic "Under-resolved turbulent flow simulations"

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Lawson, Michael J., Jeremy Melvin, Shreyas Ananthan, Kenny M. Gruchalla, Jonathan S. Rood, and Michael A. Sprague. Blade-Resolved, Single-Turbine Simulations Under Atmospheric Flow. Office of Scientific and Technical Information (OSTI), January 2019. http://dx.doi.org/10.2172/1493479.

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