Gabor Mode Enrichment in Large Eddy Simulation of Turbulent Flows

Gabor Mode Enrichment in Large Eddy Simulation of Turbulent Flows
Author: Aditya Suresh Ghate
Publisher:
Total Pages:
Release: 2018
Genre:
ISBN:

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.

Large-Eddy Simulations of Turbulence

Large-Eddy Simulations of Turbulence
Author: M. Lesieur
Publisher: Cambridge University Press
Total Pages: 240
Release: 2005-08-22
Genre: Mathematics
ISBN: 9780521781244

Large-Eddy Simulations of Turbulence is a reference for LES, direct numerical simulation and Reynolds-averaged Navier-Stokes simulation.

Large Eddy Simulation for Incompressible Flows

Large Eddy Simulation for Incompressible Flows
Author: P. Sagaut
Publisher: Springer Science & Business Media
Total Pages: 600
Release: 2006
Genre: Computers
ISBN: 9783540263449

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."

Quality and Reliability of Large-Eddy Simulations

Quality and Reliability of Large-Eddy Simulations
Author: Johan Meyers
Publisher: Springer Science & Business Media
Total Pages: 390
Release: 2008-06-26
Genre: Science
ISBN: 1402085788

Computational resources have developed to the level that, for the first time, it is becoming possible to apply large-eddy simulation (LES) to turbulent flow problems of realistic complexity. Many examples can be found in technology and in a variety of natural flows. This puts issues related to assessing, assuring, and predicting the quality of LES into the spotlight. Several LES studies have been published in the past, demonstrating a high level of accuracy with which turbulent flow predictions can be attained, without having to resort to the excessive requirements on computational resources imposed by direct numerical simulations. However, the setup and use of turbulent flow simulations requires a profound knowledge of fluid mechanics, numerical techniques, and the application under consideration. The susceptibility of large-eddy simulations to errors in modelling, in numerics, and in the treatment of boundary conditions, can be quite large due to nonlinear accumulation of different contributions over time, leading to an intricate and unpredictable situation. A full understanding of the interacting error dynamics in large-eddy simulations is still lacking. To ensure the reliability of large-eddy simulations for a wide range of industrial users, the development of clear standards for the evaluation, prediction, and control of simulation errors in LES is summoned. The workshop on Quality and Reliability of Large-Eddy Simulations, held October 22-24, 2007 in Leuven, Belgium (QLES2007), provided one of the first platforms specifically addressing these aspects of LES.

Mathematics of Large Eddy Simulation of Turbulent Flows

Mathematics of Large Eddy Simulation of Turbulent Flows
Author: Luigi Carlo Berselli
Publisher: Springer Science & Business Media
Total Pages: 378
Release: 2006
Genre: Computers
ISBN: 9783540263166

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

Direct and Large Eddy Simulation of Turbulence

Direct and Large Eddy Simulation of Turbulence
Author: NA Schumann
Publisher: Springer Science & Business Media
Total Pages: 350
Release: 2013-04-17
Genre: Technology & Engineering
ISBN: 3663001970

This volume contains papers presented to a EUROMECH-Colloquium held in Munich, September 30 to October 2, 1985. The Colloquium is number 199 in a series of colloquia inaugurated by the European Mechanics Committee. The meeting was jointly organized by the 'Lehrstuhl fur Stromungsmechanik' at the 'Technische Universitat Munchen' and the 'Institut fur Physik der Atmosphare' of the 'Deutsche Forschungs- und Versuchsanstalt fur Luft- und Raumfahrt' (DFVLR) in Oberpfaffenhofen. 'Direct' and 'large eddy simulation' are terms which denote two closely con nected methods of turbulence research. In a 'direct simulation' (DS), turbu lent motion is simulated by numerically integrating the Navier-Stokes equations in three-dimensional space and as a function of time. Besides ini tial and boundary conditions no physical simplifications are involved. Com puter resources limit the resolution in time and space, though simulations with an order of one million discrete points in space are feasible. The simu lated flow fields can be considered as true realizations of turbulent flow fields and analysed to answer questions on the basic behaviour of turbulence. Direct simulations are valid as long as all the excited scales remain within the band of resolved scales. This means that viscosity must be strong enough to damp out the not resolved scales or the simulation is restricted to a lim ited integration-time interval only. In summary, DS provides a tool to investigate turbulent motions from first principles at least for a finite band of scales.

Large Eddy Simulation for Compressible Flows

Large Eddy Simulation for Compressible Flows
Author: Eric Garnier
Publisher: Springer Science & Business Media
Total Pages: 280
Release: 2009-08-11
Genre: Science
ISBN: 9048128196

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.

Large Eddy Simulation for Incompressible Flows

Large Eddy Simulation for Incompressible Flows
Author: Pierre Sagaut
Publisher: Springer Science & Business Media
Total Pages: 326
Release: 2013-03-09
Genre: Science
ISBN: 3662044161

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."

Large Eddy Simulation of Complex Engineering and Geophysical Flows

Large Eddy Simulation of Complex Engineering and Geophysical Flows
Author: Boris Galperin
Publisher: Cambridge University Press
Total Pages: 626
Release: 1993-11-26
Genre: Technology & Engineering
ISBN: 0521430097

Originally published in 1993, this book was the first to offer a comprehensive review of large eddy simulations (LES) - the history, state of the art, and promising directions for research. Among topics covered are fundamentals of LES; LES of incompressible, compressible, and reacting flows; LES of atmospheric, oceanic, and environmental flows; and LES and massivelt parallel computing. The book grew out of an international workshop that, for the first time, brought together leading researchers in engineering and geophysics to discuss developments and applications of LES models in their respective fields. It will be of value to anyone with an interest in turbulence modelling.

Direct and Large-Eddy Simulation

Direct and Large-Eddy Simulation
Author: Bernard J. Geurts
Publisher: Walter de Gruyter GmbH & Co KG
Total Pages: 343
Release: 2022-12-05
Genre: Mathematics
ISBN: 3110531828

This book presents a comprehensive overview of the mathematics and physics behind the simulation of turbulent flows and discusses in detail (i) the phenomenology of turbulence in fluid dynamics, (ii) the role of direct and large-eddy simulation in predicting these dynamics, (iii) the multiple considerations underpinning subgrid modelling, and, (iv) the issue of validation and reliability resulting from interacting modelling and numerical errors.