Bulletin of the American Physical Society
2005 58th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 20–22, 2005; Chicago, IL
Session GP: Turbulence Simulations: LES I |
Hide Abstracts |
Chair: Krishnan Mahesh, University of Minnesota Room: Hilton Chicago Stevens 1 |
Monday, November 21, 2005 10:34AM - 10:47AM |
GP.00001: An EDQNM-based analysis on the effect of numerical errors in LES Noma Park, Krishnan Mahesh LES is known to be influenced by errors due to numerical discretization. Conventional linear analysis using modified wavenumbers does not account for the nonlinearity of turbulent flows. Static error analysis based on the power spectral density of the error terms (Ghosal, J. Comput. Phys. \textbf {125}, 1996) neglects the dynamic evolution of the solution. This paper presents a dynamic error analysis procedure based on EDQNM theory, and applies it to the LES of isotropic turbulence. The effects of finite-differencing error, aliasing error and the dynamic Smagorinsky model are incorporated into the one- dimensional equation for turbulent kinetic energy. Both collocated and staggered discretizations are considered. The proposed model equation shows good agreement with actual three- dimensional LES results. It is shown that the impact of numerical error on LES solution is overestimated by the conventional analysis and that the existence of numerical error does not overshadow the role of SGS model. [Preview Abstract] |
Monday, November 21, 2005 10:47AM - 11:00AM |
GP.00002: Large-Eddy Simulation of Turbulent Flows with Thermal Radiation and Turbulence/Radiation Interaction Daniel Haworth, Varun Singh, Ankur Gupta, Michael Modest Standard subgrid-scale turbulence models and commercial CFD solvers (FLUENT and STAR-CD) have been employed to explore turbulence/radiation interaction (TRI) using large-eddy simulation (LES). The configuration is planar turbulent channel flow between two infinite, parallel, stationary, plates at different constant temperatures. First, the capabilities and limitations of the codes in predicting correct turbulent velocity and passive temperature field statistics were established through comparisons to DNS data from the literature. Next, a radiative transfer equation solution was added using either spherical harmonics (P1) or discrete- ordinates methods. Radiation properties correspond to a fictitious gray gas with a temperature-dependent Planck-mean absorption coefficient that mimics that of typical hydrocarbon- air combustion products. Simulations were performed for different optical thicknesses. In the absence of chemical reaction, temperature fluctuations and TRI are small, consistent with earlier findings. The addition of chemical reaction enhances the temperature fluctuations, and hence the importance of TRI. This study represents a first step towards using LES to explore and model thermal radiation and TRI in chemically reacting turbulent flows. [Preview Abstract] |
Monday, November 21, 2005 11:00AM - 11:13AM |
GP.00003: Hybrid RANS/LES of non-equilibrium boundary layer flows Anthony Keating, Giuseppe De Prisco, Ugo Piomelli At high Reynolds numbers, large-eddy simulations (LES) of turbulent flows are presently infeasible due to their high cost. As an alternative, hybrid simulations can be performed in which different regions of the flow are modeled using different turbulence modeling methodologies. For instance, the Reynolds-averaged Navier-Stokes (RANS) equations can be used in equilibrium boundary layers, in which they give reasonably accurate results, whereas in highly non-equilibrium regions (where RANS models fail) LES can be used. We have performed hybrid RANS/LES simulations of boundary layers in favorable and adverse pressure gradients, where RANS is used near equilibrium and LES is performed in the highly non-equilibrium regions. When synthetic turbulence by itself is used to couple the RANS and LES regions, the flow laminarizes in the LES region, and the results show poor agreement with a full LES. To improve results, an overlap region is used, where forcing is applied to the LES in order to match the RANS shear stress. When this is done, the hybrid simulations show excellent agreement with the full LES. This research was supported by the AFOSR. [Preview Abstract] |
Monday, November 21, 2005 11:13AM - 11:26AM |
GP.00004: Coherent Structure Dynamics of the Horse Vortex System Induced by a Circular Cylindrical Pier Mounted on a Flat Plate at Re=39,000 Cristian Escauriaza, Joongcheol Paik, Fotis Sotiropoulos A critical prerequisite for developing predictive computational models of sediment transport and scour in real-life bridge foundations is the numerical simulation of the foundation induced large-scale, coherent vortices at full-scale Reynolds numbers. We simulate the turbulent flow past a single cylindrical pier mounted on a smooth flat bed using an overset grid approach in conjunction with a coherent structure resolving statistical turbulence model; Spalart’s Detached Eddy Simulation (DES) approach (Spalart et al. in Advance in DNS/LES, 1997). The computed results are compared with Dargahi’s (Experiments in Fluids, Vol. 8, p. 1, 1989) flow visualizations and mean flow measurements in the geometrical configuration, and analyzed to elucidate the rich physics of the flow in the upstream region of the cylinder, which is dominated by the low frequency unsteadiness of the horseshoe vortex system. The interaction of the HV system with the cylinder wake is also examined in detail. [Preview Abstract] |
Monday, November 21, 2005 11:26AM - 11:39AM |
GP.00005: DES of Turbulent Flow Past a Wall-Mounted Wing Joongcheol Paik, Fotis Sotiropoulos In a pioneering experimental study, Devenport and Simpson (J. Fluid Mech. Vol. 210, p. 23, 1990) showed experimentally that the horseshoe vortex system in the leading edge region of a symmetric wing mounted on a flat plate is dominated by low-frequency, coherent unsteadiness. These slowly evolving coherent vortices were shown to account for a considerable portion of the total production of turbulence kinetic energy and to give rise to bi-modal velocity pdfs. We carry out Detached Eddy Simulation (Spalart et al. in Advance in DNS/LES, 1997) of the flow past the Devenport and Simpson’s wing using an overset grid approach that locally embeds fine mesh resolution in the vicinity of the horseshoe vortex system. The computed results confirm the experimental findings concerning the low frequency, rich dynamics of the horseshoe vortex system. Detailed quantitative comparisons with the measurements and analysis of the 3D structure of the coherent structures in the flow will be presented at the conference. [Preview Abstract] |
Monday, November 21, 2005 11:39AM - 11:52AM |
GP.00006: Modeling turbulent flow over fractal trees with Renormalized Numerical Simulation (RNS) Stuart Chester, Charles Meneveau, Marc B. Parlange Ideas from dynamic LES and renormalization group theory are applied to the problem of modeling SGS branch drag for turbulent flow over trees. The drag on SGS branches is modeled using a drag coefficient, which is not known a priori due to the complexity of the flow. The drag coefficient is determined by making measurements within the simulation at resolved scales and using dimensional analysis to downscale this information for application at sub-grid scales. This Renormalized Numerical Simulation (RNS) strategy is tested by comparing coarse RNS to high-resolution, branch-resolving simulations. Two idealized fractal geometries are used: one with all branches aligned across the mean flow, and one with additional branches that point upstream and downstream. The overall drag on the tree is well-predicted by the RNS, and non-trivial differences in drag coefficients for branches with different orientations are observed. Results from two formulations, one using direct calculation and the other using an analogue of the Germano identity (Germano et. al., 1991), are also compared. [Preview Abstract] |
Monday, November 21, 2005 11:52AM - 12:05PM |
GP.00007: The Lagrangian nature of turbulent energy cascade Minping Wan, Shiyi Chen, Charles Meneveau, Zuoli Xiao, Gregory Eyink We study the spatial and temporal evolution of energy flux at different scales using direct numerical simulations of isotropic turbulence. We compute the correlation coefficient at different times, between energy dissipation and local energy fluxes across inertial-range scales, in both Eulerian and Lagrangian frames. For the latter, we use a backward particle-tracking method. The Eulerian correlation coefficients decay monotonically, backward in time. However, the Lagrangian correlation coefficients between flux at adjacent scales peak after a certain time delay, which scales as the local turnover time. This result provides strong evidence of the Lagrangian nature of turbulent energy cascade. We present results on similar correlations in the two-dimensional inverse energy cascade range, and discuss the differences with three- dimensional forward energy cascade. [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