Bulletin of the American Physical Society
68th Annual Meeting of the APS Division of Fluid Dynamics
Volume 60, Number 21
Sunday–Tuesday, November 22–24, 2015; Boston, Massachusetts
Session E20: Turbulence: Large Eddy Simulations |
Hide Abstracts |
Chair: Rayhaneh Akhavan, University of Michigan Room: 208 |
Sunday, November 22, 2015 4:50PM - 5:03PM |
E20.00001: Computations of turbulent channel flow using the nested-LES approach Rayhaneh Akhavan, Yifeng Tang Nested-LES is an approach to computing high Reynolds wall-bounded turbulent flows based on coarse-resolution LES in the full-domain, coupled with nested, well-resolved LES in a minimal flow unit. The two domains are coupled by renormalizing the instantaneous LES velocity fields, at each time-step during the course of the simulation, to match the profiles of kinetic energies of the components of the mean velocity and velocity fluctuations in both domains to those of the minimal flow unit in the near-wall region, and to those of the full-domain in the outer region. The method reduces the required number of grid points from $O(Re_\tau^2)$ of conventional LES to $O(\log Re_\tau)$ and $O(Re_\tau)$ in flows with two and one locally or globally homogeneous directions, respectively. In this talk, we review the results obtained with nested-LES in turbulent channel flow at $1000 \le Re_\tau \le 10000$. It is shown that nested-LES predicts not only the first-order statistics, but also all higher-order moments, spectra, and structural features of the flow in agreement with DNS and experimental results. The details of the optimal construction of the grid to achieve these results and the principles behind nested-LES will be discussed. [Preview Abstract] |
Sunday, November 22, 2015 5:03PM - 5:16PM |
E20.00002: A metric for assessing the dynamic content of large-eddy simulations Gabriel Nastac, Matthias Ihme Current metrics used to identify the quality of large-eddy simulations commonly rely on a statistical assessment of the solution. While these metrics are valuable, turbulence is inherently a dynamic phenomenon, so a dynamic measure is desirable to characterize the quality of a numerical prediction. A dynamic metric utilizing a form of Lyapunov exponents and error growth rates is proposed and applied to two test cases: homogenous isotropic turbulence and a turbulent jet diffusion flame. A grid refinement analysis is performed for each test case utilizing this dynamic metric and current results show monotonic trends versus LES filter width. Results for the homogenous isotropic turbulence show insights into the effect of LES-resolution on the initial rapid error growth rate. [Preview Abstract] |
Sunday, November 22, 2015 5:16PM - 5:29PM |
E20.00003: Discrete dynamical system approximation to the Boltzmann equation for eddy-viscosity-free LES modeling of transitional flow J. M. McDonough, Huidan (Whitney) Yu A discrete dynamical system (DDS) representation of the Boltzmann equation with the BGK approximation is derived. The density distribution function is constructed through a single-mode Fourier--Galerkin approximation with basis functions in coordinate space but Fourier coefficients depending on time and molecular velocity. The resulting DDS contains numerous bifurcation parameters related to various physical quantities, and effects of varying these parameters on temporal behavior of distribution function Fourier coefficients are studied through time series and power spectra by means of which types of dynamical behavior are identified. It is found that the DDS can produce all of steady, periodic, sub-harmonic, quasi-periodic, phase-locked and chaotic time series as bifurcation parameters are changed; in addition, the chaotic regimes exhibit various forms of intermittency. An approach to employing this DDS as part of a subgrid-scale model for eddy-viscosity-free, multi-scale large-eddy simulation employing the lattice Boltzmann equation is described. [Preview Abstract] |
Sunday, November 22, 2015 5:29PM - 5:42PM |
E20.00004: Autonomic Closure for Large Eddy Simulation Ryan King, Peter Hamlington, Werner J. A. Dahm A new autonomic subgrid-scale closure has been developed for large eddy simulation (LES). The approach poses a supervised learning problem that captures nonlinear, nonlocal, and nonequilibrium turbulence effects without specifying a predefined turbulence model. By solving a regularized optimization problem on test filter scale quantities, the autonomic approach identifies a nonparametric function that represents the best local relation between subgrid stresses and resolved state variables. The optimized function is then applied at the grid scale to determine unknown LES subgrid stresses by invoking scale similarity in the inertial range. \textit{A priori} tests of the autonomic approach on homogeneous isotropic turbulence show that the new approach is amenable to powerful optimization and machine learning methods and is successful for a wide range of filter scales in the inertial range. In these \textit{a priori} tests, the autonomic closure substantially improves upon the dynamic Smagorinsky model in capturing the instantaneous, statistical, and energy transfer properties of the subgrid stress field. [Preview Abstract] |
Sunday, November 22, 2015 5:42PM - 5:55PM |
E20.00005: Temporal characterization of turbulence and coherent structures in a recirculating flow Jesus Ramirez-Pastran, Carlos Duque-Daza, Duncan A. Lockerby Analysis of the temporal behavior of a recirculating flow is performed by numerical experiments on a lid-driven cavity setup. Simulations at two Reynolds numbers, based on the cavity depth (Re=3200 and Re=12000), were computed for an incompressible turbulent flow using LES. Good agreement was observed with results reported for velocity profiles along vertical and horizontal planes, but discrepancies against experimental data were found for the fluctuating velocity profiles. By using long-term simulations a complex quasi-periodic behaviour is observed and a set of dominant frequencies identified. Such behaviour is also identified by examining the temporal evolution of the TKE production and viscous dissipation terms. Coherent structures based on the Q-criterion are calculated and used to characterize the quasi-periodic behavior. Simple correlations are established between the structures and the TKE terms. Results seem to indicate that the apparently unstable behaviour is promoted by the existence of two internal flow streams, located at the side walls, and which collide at a region around the centre of the cavity. It is concluded that this interaction is responsible for the appearance of the rich set of frequencies observed at the different locations within the recirculating flow. [Preview Abstract] |
Sunday, November 22, 2015 5:55PM - 6:08PM |
E20.00006: Study of dealiasing schemes in pseudo-spectral methods for Large-Eddy Simulations of incompressible flows Fabien Margairaz, Marco Giometto, Marc Parlange, Marc Calaf The performance of dealiasing schemes and their computational cost on a pseudo-spectral code are analyzed. Dealiasing is required to limit the error that occurs when two discretized variables are multiplied, polluting the accuracy of the result. In this work three different dealiasing methods are explored: the 2/3 rule, the 3/2 rule, and a high order Fourier smoothing based method. We compare the cost of the traditionally accepted 3/2 rule (Canuto et al. 1988), where an expansion of the computational domain to a larger grid is required, to the cost of the other two techniques that do not require this expansion. This analysis is performed in the framework of Large-Eddy Simulations (LES) of incompressible flows using the constant Smagorinsky sub-grid model with a wall damping function and a wall model based on the log-law. A highly efficient LES code parallelized using a 2D pencil decomposition has been developed. The code employs the traditional pseudo-spectral approach to integrate the incompressible Navier-Stokes equations. Several simulations of a neutral atmospheric boundary layer using different degrees of numerical resolution are considered. Results show a net difference in computational cost between the different techniques without relevant changes in statistics. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700