Download or read book Wavelet spectral Analysis and Large eddy Simulation Using Neural Networks of Droplet laden Decaying Isotropic Turbulence written by Andreas Freund and published by . This book was released on 2020 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this work, we propose new methods for both the analysis and simulation of droplet-laden isotropic turbulence. First, we suggest using the wavelet energy spectrum to study multiphase turbulent flows to overcome the challenges of applying the Fourier energy spectrum to velocity fields with sharp velocity gradients. Also, we propose a new decomposition of the wavelet energy spectrum into three contributions corresponding to the carrier phase, droplets, and interaction between the two. We apply these new wavelet-decomposition tools in analyzing the direct numerical simulation (DNS) data of droplet-laden decaying isotropic turbulence of Dodd & Ferrante (2016, J. Fluid Mech. 806:3560́3412). Our results show that, in comparison to the spectrum of the single-phase case, the droplets (i) do not affect the carrier-phase energy spectrum at high wavenumbers (km/kmin>̲128), (ii) increase the energy spectrum at high wavenumbers (km/kmin>̲256) by increasing the interaction energy spectrum at these wavenumbers, and (iii) decrease the energy at low wavenumbers (km/kmin

Download or read book Large Eddy Simulation for Incompressible Flows written by P. Sagaut and published by Springer Science & Business Media. This book was released on 2006 with total page 600 pages. Available in PDF, EPUB and Kindle. Book excerpt: First concise textbook on Large-Eddy Simulation, a very important method in scientific computing and engineering From the foreword to the third edition written by Charles Meneveau: "... this meticulously assembled and significantly enlarged description of the many aspects of LES will be a most welcome addition to the bookshelves of scientists and engineers in fluid mechanics, LES practitioners, and students of turbulence in general."

Download or read book Large Eddy Simulation for Incompressible Flows written by Pierre Sagaut and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: First concise textbook on Large-Eddy Simulation, a very important method in scientific computing and engineering From the foreword to the third edition written by Charles Meneveau: "... this meticulously assembled and significantly enlarged description of the many aspects of LES will be a most welcome addition to the bookshelves of scientists and engineers in fluid mechanics, LES practitioners, and students of turbulence in general."

Download or read book Large Eddy Simulation of Turbulent Incompressible Flows written by Volker John and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: Large eddy simulation (LES) seeks to simulate the large structures of a turbulent flow. This is the first monograph which considers LES from a mathematical point of view. It concentrates on LES models for which mathematical and numerical analysis is already available and on related LES models. Most of the available analysis is given in detail, the implementation of the LES models into a finite element code is described, the efficient solution of the discrete systems is discussed and numerical studies with the considered LES models are presented.

Download or read book Mathematics of Large Eddy Simulation of Turbulent Flows written by Luigi Carlo Berselli and published by Springer Science & Business Media. This book was released on 2006 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: The LES-method is rapidly developing in many practical applications in engineering The mathematical background is presented here for the first time in book form by one of the leaders in the field

Download or read book Direct and Large Eddy Simulation IV written by Bernard Geurts and published by Springer Science & Business Media. This book was released on 2001-11-30 with total page 554 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume contains the proceedings of the 2001 DLES4 workshop. It describes and discusses state-of-the-art modeling and simulation approaches for complex flows. Fundamental turbulence and modeling issues but also elements from modern numerical analysis are at the heart of this field of interest.

Download or read book Direct and Large Eddy Simulation X written by Dimokratis G.E. Grigoriadis and published by Springer. This book was released on 2017-10-06 with total page 523 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses nearly all aspects of the state of the art in LES & DNS of turbulent flows, ranging from flows in biological systems and the environment to external aerodynamics, domestic and centralized energy production, combustion, propulsion as well as applications of industrial interest. Following the advances in increased computational power and efficiency, several contributions are devoted to LES & DNS of challenging applications, mainly in the area of turbomachinery, including flame modeling, combustion processes and aeroacoustics. The book includes work presented at the tenth Workshop on 'Direct and Large-Eddy Simulation' (DLES-10), which was hosted in Cyprus by the University of Cyprus, from May 27 to 29, 2015. The goal of the workshop was to establish a state of the art in DNS, LES and related techniques for the computation and modeling of turbulent and transitional flows. The book is of interest to scientists and engineers, both in the early stages of their career and at a more senior level.

Download or read book Direct and Large Eddy Simulation VIII written by Hans Kuerten and published by Springer Science & Business Media. This book was released on 2011-10-05 with total page 460 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume continues previous DLES proceedings books, presenting modern developments in turbulent flow research. It is comprehensive in its coverage of numerical and modeling techniques for fluid mechanics. After Surrey in 1994, Grenoble in 1996, Cambridge in 1999, Enschede in 2001, Munich in 2003, Poitiers in 2005, and Trieste in 2009, the 8th workshop, DLES8, was held in Eindhoven, The Netherlands, again under the auspices of ERCOFTAC. Following the spirit of the series, the goal of this workshop is to establish a state-of-the-art of DNS and LES techniques for the computation and modeling of transitional/turbulent flows covering a broad scope of topics such as aerodynamics, acoustics, combustion, multiphase flows, environment, geophysics and bio-medical applications. This gathering of specialists in the field was a unique opportunity for discussions about the more recent advances in the prediction, understanding and control of turbulent flows in academic or industrial situations.

Download or read book Large Eddy Simulation of Particle Laden Flow written by Christian Gobert and published by Sudwestdeutscher Verlag Fur Hochschulschriften AG. This book was released on 2010 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is a contribution to research in the field of Large Eddy Simulation (LES) of particle-laden flow with a focus on the effect of unresolved small scale turbulence on suspended particles. The first substantial contribution of this thesis is a detailed quantification of small scale effects in homogeneous isotropic turbulence. The second contribution of this thesis is an analytical and numerical analysis of three commonly used models that describe the effect of subgrid scales on particles: the Approximate Deconvolution Method (ADM) and two stochastic models. The third contribution is a new model that can be regarded as an extension of ADM. The new model consists of a specific interpolation method, which is designed such that statistically the numerical interpolation error can be identified with the effect of the unresolved scales. The new model is computationally inexpensive and in the analysed testcases more accurate than the previously analysed models.

Download or read book Machine Learning Methods for Modeling Turbulence in Large Eddy Simulations written by Marius Kurz and published by . This book was released on 2024 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The reliable prediction of turbulent flows is of crucial importance since turbulence is prevalent in the majority of flows found in science and engineering. Turbulence is a multi-scale phenomenon, for which flow features can span several orders of magnitude in size. This results in enormous resolution requirements in numerical simulations of turbulent flow. The framework of large eddy simulation relaxes these resolution demands by resolving only the largest, most energetic features of the flow and approximating the dynamics of the smaller, unresolved scales with turbulence models. The goal of this thesis is to leverage the recent advances in machine learning methods to formulate data-driven modeling strategies for implicitly filtered large eddy simulation. To this end, two modeling strategies are devised based on the supervised and the reinforcement learning paradigms. First, artificial neural networks are trained using supervised learning to recover the unknown closure terms from the filtered flow field. It is demonstrated that recurrent neural networks can predict the unknown closure terms with excellent accuracy. The second modeling strategy is based on the reinforcement learning paradigm. For this, Relexi is introduced as a novel reinforcement learning framework that allows to employ legacy flow solvers as training environments at scale. With Relexi, artificial neural networks are trained within forced homogeneous isotropic turbulence to adapt the parameters of traditional turbulence models dynamically in space and time. The trained models provide accurate and stable simulations and generalize well to other resolutions and higher Reynolds numbers. It is demonstrated within this thesis that machine learning methods can be applied to derive data-driven turbulence models for implicitly filtered large eddy simulation and that these models can be trained and incorporated efficiently into practical simulations on high-performance computing systems.

Download or read book Parametric study of decay of homogeneous isotropic turbulence using large eddy simulation written by and published by . This book was released on 2012 with total page 69 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optimal Large Eddy Simulation of Turbulence written by Robert deLancey Moser and published by . This book was released on 2004 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Gabor Mode Enrichment in Large Eddy Simulation of Turbulent Flows written by Aditya Suresh Ghate and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Buoyed by the rise in computational capabilities, eddy resolving simulation methodologies such as Large Eddy Simulation (LES), first developed in 1970s, have now come to dominate academic research in numerical simulation of turbulent flows. Wall-modeled LES (WMLES) which alleviates the no-slip boundary condition at walls with a stress condition computed using either a physics based or a mathematically derived boundary condition based on the filtering kernel, has further enabled the use of LES in applications involving very high Reynolds number wall bounded flows. Motivated by this growing success and push for use of WMLES in both engineering and geophysics communities, we address a new emerging challenge in this field: Given a robust characterization of the large scales, can we come up with a reasonably consistent synthesis of the unresolved/subfilter scales at low computational cost? This is a particularly pertinent question in wall bounded flows since several applications that involve unsteady loads, surface vibrations, acoustic radiation, etc. require near wall representation of turbulent scales with a spatio-temporal bandwidth substantially larger than that implied by WMLES. This problem naturally arises in wind energy applications where the Planetary Boundary Layer (PBL) turbulence at extreme Reynolds numbers can only be resolved up to scales much larger than the chord lengths of wind turbine blades. Other multiphysics applications such as particle laden turbulence also require spectral resolution of the explicitly resolved fluid turbulence to be larger than what is typically available in LES. The method developed in this thesis is based on combining a scale-resolving turbulence simulation (such as WMLES) with limited bandwidth, with an efficient, physics-based scale-enrichment model. The enrichment scheme generates a physically consistent realization of the finer-scale eddies locally which dynamically respond to the resolved larger scales and enable statistical predictions of physical quantities with a substantially larger bandwidth. This physics based model is carefully constructed to obtain small scales with accurate second-order space-time correlations. By representing the small scales using \emph{Gabor modes/wavepackets}, there is a substantial compression in degrees of freedom. Furthermore, the use of WKB-variant of Rapid Distortion Theory (RDT) along with a spectral viscosity closure allows for temporal evolution of the Gabor modes via a set of ODEs described in an x-k frame. Use of spatially and spectrally localized Gabor modes ensures correct inter-scale energy transfer and allows for treatment of spatial inhomogeneities. The transform of physical field variables from their Gabor modes representation to the physical space is accomplished using modern non-uniform FFT algorithms thereby achieving an overall nlog(n) computational cost. Robustness of this new method is assessed on various wall-bounded flow configurations (including a problem with Coriolis acceleration and stratification) using a representation of large scales obtained using both ideal WMLES (filtered DNS) and realistic/true WMLES simulations at high Reynolds numbers. While the enrichment of large scales obtained via idealized LES is excellent, the results for realistic LES are also very promising. Finally, we discuss a highly idealized problem to study the interaction of free-stream (isotropic) turbulence with a turbulent wake generated by an actuator disk. Beyond characterizing the flow physics in detail, we present evidence suggesting that the recovery and entrainment in the wake is much more sensitive to the integral length scale of the ambient turbulence, than its intensity. Furthermore, the incident flow seen by a downstream object present in the wake, has no low-rank behavior in terms of space-time coherence. We subsequently demonstrate that a truncated reconstruction of the flow field using space-time POD modes can be enriched with fine scales using Gabor modes to recover the full bandwidth of the high resolution simulation.

Download or read book Spectral Analysis of the Turbulent Energy Cascade and the Development of a Novel Nonlinear Subgrid scale Model for Large Eddy Simulation written by João Rodrigo Andrade and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of the present work is to analyze and to provide an enhancement of the knowledge about the subgrid-scale behavior and to propose novel nonlinear subgrid-scale models for large eddy simulations of turbulent fluid flows. In this way, the present thesis is subdivided into three main parts. The first topic is an analysis of the statistical uncertainties associated with direct numerical simulation data for turbulent channel flow, showing a novel physicallybased quantification of these errors. In this analysis, the mean velocity error is estimated by considering the Reynolds stress tensor, and using the balance of mean force equation. This analysis is performed in order to verify the quality of the statistical data coming from the direct numerical simulation applied in the present work. Secondly, seeking to understand the contained physics in the whole wavenumber spectrum of turbulent flows, an analysis of the spectral turbulent kinetic energy budget in fully developed turbulent plane channel flow is performed. The analysis is focused on the influence of the Reynolds number on the spectral cascade of energy and the corresponding energy cascade in physical space in the presence of inhomogeneity and anisotropy. Finally, a novel nonlinear subgrid-scale model for large eddy simulation based on a set of objective tensors is presented. In the proposed closure model, the modeled subgrid-scale stress tensor is a function of the resolved rate-of-strain tensor and the resolved non-persistence-of-straining tensor, where both are local and objective kinematic entities. The non-persistence-of-straining tensor represents the local ability of the fluid to avoid being persistently stretched. To check the consistency of the proposed model, a priori and a posteriori tests are performed by simulating different wall-bounded turbulent flows. Comparisons with the exact subgrid-scale stress tensor and experimental data revealed that the inclusion of nonlinear terms on the subgrid-scale model can significantly increase the accuracy of the results, showing the great potential of the proposed tensorial base.

Download or read book Large Eddy Simulation for Compressible Flows written by Eric Garnier and published by Springer. This book was released on 2009-08-19 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book addresses both the fundamentals and the practical industrial applications of Large Eddy Simulation (LES) in order to bridge the gap between LES research and the growing need to use it in engineering modeling.

Download or read book Statistical Closure to Derive a Subgrid scale Modeling for Large Eddy Simulations of Three dimensional Turbulence written by Jean-Pierre Chollet and published by . This book was released on 1983 with total page 50 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Direct and Large eddy Simulation XI written by Maria Vittoria Salvetti and published by . This book was released on 2019 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers the proceedings of the 11th workshop on Direct and Large Eddy Simulation (DLES), which was held in Pisa, Italy in May 2017. The event focused on modern techniques for simulating turbulent flows based on the partial or full resolution of the instantaneous turbulent flow structures, as Direct Numerical Simulation (DNS), Large-Eddy Simulation (LES) or hybrid models based on a combination of LES and RANS approaches. In light of the growing capacities of modern computers, these approaches have been gaining more and more interest over the years and will undoubtedly be developed and applied further. The workshop offered a unique opportunity to establish a state-of-the-art of DNS, LES and related techniques for the computation and modeling of turbulent and transitional flows and to discuss about recent advances and applications. This volume contains most of the contributed papers, which were submitted and further reviewed for publication. They cover advances in computational techniques, SGS modeling, boundary conditions, post-processing and data analysis, and applications in several fields, namely multiphase and reactive flows, convection and heat transfer, compressible flows, aerodynamics of airfoils and wings, bluff-body and separated flows, internal flows and wall turbulence and other complex flows.