Boundary conditions for direct simulations of compressible viscous flows

This book is a tutorial written by researchers and developers behind the FEniCS Project and explores an advanced, expressive approach to the development of mathematical software. The presentation spans mathematical background, software design and the use of FEniCS in applications. Theoretical aspects are complemented with computer code which is available as free/open source software. The book begins with a special introductory tutorial for beginners. Followingare chapters in Part I addressing fundamental aspects of the approach to automating the creation of finite element solvers. Chapters in Part II address the design and implementation of the FEnicS software. Chapters in Part III present the application of FEniCS to a wide range of applications, including fluid flow, solid mechanics, electromagnetics and geophysics.

Automated Solution of Differential Equations by the Finite Element Method: The FEniCS Book

A critical review of the intrinsic nature of vortex-induced vibrations

Strategies for turbulence modelling and simulations

This is a personal statement on the present state of understanding of coherent structures, in particular their spatial details and dynamical significance. The characteristic measures of coherent structures are discussed, emphasizing coherent vorticity as the crucial property. We present here a general scheme for educing structures in any transitional or fully turbulent flow. From smoothed vorticity maps in convenient flow planes, this scheme recognizes patterns of the same mode and parameter size, and then phase-aligns and ensemble-averages them to obtain coherent structure measures. The departure of individual realizations from the ensemble average denotes incoherent turbulence. This robust scheme has been used to educe structures from velocity data using a rake of hot wires as well as direct numerical simulations and can educe structures using newer measurement techniques such as digital image processing. Our recent studies of coherent structures in several free shear flows are briefly reviewed. Detailed data in circular and elliptic jets, mixing layers, and a plane wake reveal that incoherent turbulence is produced at the ‘saddles’ and then advected to the ‘centres’ of the structures. The mechanism of production of turbulence in shear layers is the stretching of longitudinal vortices or ‘ribs’ which connect the predominantly spanwise ‘rolls’; the ribs induce spanwise contortions of rolls and cause mixing and dissipation, mostly at points where they connect with rolls. We also briefly discuss the role of coherent structures in aerodynamic noise generation and argue that the structure breakdown process, rather than vortex pairing, is the dominant mechanism of noise generation. The ‘cut-and-connect’ interaction of coherent structures is proposed as a specific mechanism of aerodynamic noise generation, and a simple analytical model of it shows that it can provide acceptable predictions of jet noise. The coherent-structures approach to turbulence, apart from explaining flow physics, has also enabled turbulence management via control of structure evolution and interactions. We also discuss some new ideas under investigation: in particular, helicity as a characteristic property of coherent structures.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0022112086001192

Coherent structures and turbulence.

https://iopscience.iop.org/article/10.1016/0169-5983(92)90023-P/pdf

New Insights into Large Eddy Simulation

Fluid dynamic turbulence is one of the most challenging computational physics problems because of the extremely wide range of time and space scales involved, the strong nonlinearity of the governing equations, and the many practical and important applications. While most linear fluid instabilities are well understood, the nonlinear interactions among them makes even the relatively simple limit of homogeneous isotropic turbulence difficult to treat physically, mathematically, and computationally. Turbulence is modeled computationally by a two-stage bootstrap process. The first stage, direct numerical simulation, attempts to resolve the relevant physical time and space scales but its application is limited to diffusive flows with a relatively small Reynolds number (Re). Using direct numerical simulation to provide a database, in turn, allows calibration of phenomenological turbulence models for engineering applications. Large eddy simulation incorporates a form of turbulence modeling applicable when the large-scale flows of interest are intrinsically time dependent, thus throwing common statistical models into question. A promising approach to large eddy simulation involves the use of high-resolution monotone computational fluid dynamics algorithms such as flux-corrected transport or the piecewise parabolic method which have intrinsic subgrid turbulence models coupled naturally to the resolved scales in the computed flow. The physical considerations underlying and evidence supporting this monotone integrated large eddy simulation approach are discussed.

New insights into large eddy simulation

Introduction Fernando Grinstein, Len Margolin and William Rider Part I. Motivation: 1. Historical introduction Jay Boris 2. ILES for turbulent flows: a rationale Fernando Grinstein, Len Margolin and William Rider Part II. Capturing Physics with Numerics: 3. Subgrid scale modeling: issues and approaches Pierre Sagaut 4. Numerics for ILES 4a. Limiting algorithms Dimitris Drikakis, Marco Hahn, Fernando Grinstein, Carl DeVore, Christer Fureby, Mattias Liefvendahl and David Youngs 4b. Piecewise parabolic method Paul Woodward 4c. Lagrangean remap method David Youngs 4d. MPDATA Piotr Smolarkiewicz and Len Margolin 4e. Vorticity confinement John Steinhoff, Nicholas Lynn and Lesong Wang 5. Numerical regularization Len Margolin and William Rider 6. Approximate deconvolution Nikolaus Adams and J. A. Domaradzki Part III. Verification and Validation: 7. Homogeneous turbulence David Porter and Paul Woodward 8. Vortex dynamics and transition in free shear flows Fernando Grinstein 9. Symmetry bifurcation and instabilities Dimitris Drikakis 10. Incompressible wall bounded flows Christer Fureby, Mattias Liefvendahl, Urban Svennberg, Leif Persson and Tobias Persson 11. Compressible turbulent shear flows Christer Fureby and Doyle Knight 12. Studies based on vorticity confinement John Steinhoff, Nicholas Lynn, Wenren Yonghu, Meng Fan, Lesong Wang and Bill Dietz 13. Rayleigh-Taylor and Richtmyer-Meshkov mixing David Youngs Part IV. Frontier Flows: 14. Studies of geophysics Piotr Smolarkiewicz and Len Margolin 15. Studies of astrophysics David Porter and Paul Woodward 16. Complex engineering turbulent flows Niklas Alin, Magnus Berglund, Christer Fureby, Eric Lillberg and Urban Svennberg 17. Large scale urban simulations Gopal Patnaik, Fernando Grinstein, Jay Boris, Ted Young and Oskar Parmhed 18. Outlook and open research issues Fernando Grinstein, Len Margolin and William Rider.

Implicit large eddy simulation : computing turbulent fluid dynamics

Noncircular jets have been the topic of extensive research in the last fifteen years. These jets were identified as an efficient technique of passive flow control that allows significant improvements of performance in various practical systems at a relatively low cost because noncircular jets rely solely on changes in the geometry of the nozzle. The applications of noncircular jets discussed in this review include improved large- and small-scale mixing in low- and high-speed flows, and enhanced combustor performance, by improving combustion efficiency, reducing combustion instabilities and undesired emissions. Additional applications include noise suppression, heat transfer, and thrust vector control (TVC). The flow patterns associated with noncircular jets involve mechanisms of vortex evolution and interaction, flow instabilities, and fine-scale turbulence augmentation. Stability theory identified the effects of initial momentum thickness distribution, aspect ratio, and radius of curvature on the initial flow evolution. Experiments revealed complex vortex evolution and interaction related to selfinduction and interaction between azimuthal and axial vortices, which lead to axis switching in the mean flow field. Numerical simulations described the details and clarified mechanisms of vorticity dynamics and effects of heat release and reaction on noncircular jet behavior.

Flow control with noncircular jets

With a view to ensure that proper interaction between resolvable or grid scale and subgrid scale (SGS) motions are mimicked, it is vital to determine the necessary physics that must be built into the SGS models. In ordinary large eddy simulation (LES) approaches, models are introduced for closure in the low-pass filtered Navier-Stokes equations (NSEs), which are the ones solved numerically. A promising LES approach is monotonically integrated LES (MILES), which involves solving the unfiltered NSE using high-resolution monotone algorithms; in this approach, implicit SGS models, provided by intrinsic nonlinear high-frequency filters built into the convection discretization, are coupled naturally to the resolvable scales of the flow. Formal properties of the effectual SGS modeling using MILES are documented using databases of simulated homogeneous turbulence and transitional freejets; mathematical and physical aspects of (implicit) SGS modeling through the use of nonlinear flux limiters are addressed in this context

Fernando F. Grinstein

Papers

New Insights into Large Eddy Simulation

New insights into large eddy simulation

Implicit large eddy simulation : computing turbulent fluid dynamics

Flow control with noncircular jets

Monotonically integrated large eddy simulation of free shear flows