Large-Eddy Simulations

Shaw and Schumann [576] were the first to apply LES to the canopy environment in attempts to reproduce characteristics of the flow through and above a deciduous forest. The code numerically solves the basic conservation equations for momentum and heat with options for additional scalars. For flow through a horizontally homogeneous canopy on uniform terrain, the momentum equation appears in the following manner  

Large-eddy simulation output is a three-dimensional, time-dependent flow and scalar field. The results are unique in reproducing most aspects of the turbulent flow field and its interaction with a layer of vegetation. Due to the considerable demand on computational resources, it is not yet reasonable to utilize a grid network that can sufficiently resolve a vegetation canopy and, at the same time, extend both horizontally and vertically to simulate a full atmospheric boundary layer. Nevertheless, even simulations with quite limited vertical extent, as few as three canopy heights, have been successful in accurately reproducing the features described earlier. 

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Another detailed method of determining pressures is computational fluid dynamics (CFD), which uses a numerical solution of simplified equations of motion over a dense grid of points around the building. Murakami et al. and Zhoy and Stathopoulos found less agreement with computational fluid dynamics methods using the k-e turbulence model typically used in current commercial codes. More advanced turbulence models such as large eddy simulation were more successful but much more costly. ... 

David.son, L, Large eddy simulation A dynamic one-equation subgrid model for three-dimensional recirculating flow. In llth Int. Symp. on Turbulent Shear Flow, vol. 3, pp. 26.1-26.6, Grenoble, 1997. 

Davidson, L., Nielsen, P. Large eddy simulation.s of the flow in a three-dimensional ventilated room. In Murakami, S., ed. Roomvent 96 5th Int. Conf. on Air Distributions in Rooms, vol. 2, pp. 161-168, Yokohama, Japan, 1996. 

L. Duchamp de Lageneste and H. Pitsch 2001, Progress in the large eddy simulation of premixed and partially premixed turbulent combustion, in Center for Turbulence Research (CTR, Stanford) Annual Research Brief. 

The ability to resolve the dissipation structures allows a more detailed understanding of the interactions between turbulent flows and flame chemistry. This information on spectra, length scales, and the structure of small-scale turbulence in flames is also relevant to computational combustion models. For example, information on the locally measured values of the Batchelor scale and the dissipation-layer thickness can be used to design grids for large-eddy simulation (LES) or evaluate the relative resolution of LES resulfs. There is also the potential to use high-resolution dissipation measurements to evaluate subgrid-scale models for LES. 

Raman, V. and Pitsch, H., Large-eddy simulation of a bluff-body-stabilized non-premixed flame using a recursive filter-refinement procedure. Combust. Flame, 142, 329, 2005. 

Pitsch, H. and Steiner, H., Scalar mixing and dissipation rate in large-eddy simulations of non-premixed turbulent combustion, Proc. Combust. Inst., 28, 41, 2000. 

Okong o, N. and J. Bellan, Consistent large-eddy simulation of a temporal mixing layer laden with evaporating drops. Rart 1. Direct numerical simulation, formulation and a priori analysis. J. Fluid Mech., 2004. 499 1-47. 

Colin, O., et al., A thickened flame model for large-eddy simulations of turbulent premixed combustion. Phi/s. Fluids, 2000.12(7) 1843-1863. 

Moreau, M., B. Bedat, and O. Simonin, From Euler-Lagrange to Euler-Euler large eddy simulation approaches for gas-particle turbulent flows, in ASME Fluids Engineering Summer Conference, Houston. 2005, ASME FED. 

Riber, E., et al.. Towards large eddy simulation of non-homogeneous particle laden turbulent gas flows using Euler-Euler approach, in Eleventh Workshop on Two-Phase Flow Predictions. 2005, Merseburg, Germany. 

Celik, L, 1. Yavuz, and A. Smirnov, Large eddy simulations of in-cylinder turbulence for internal combustion engines A review. Int. J. Eng Res., 2001.2(2) 119-148. 

Richard, S., Colin, O., Vermorel, O., Benkenida, A., Angelberger, C., and Veynante, D., Towards large eddy simulation of combustion in spark ignition engines. Proc. Comb. Inst., 2007. 31,3059-3066. 

An approximation of the flow field by a large eddy simulation (LES) formulation of the measured large eddies gives a reasonable estimation of the dissipation rate [7]. 

Mathpati, C.S. and Joshi, J.B. (2007) Insight into theories of heat and mass transfer at the solid/fluid interface using direct numerical simulation and large eddy simulation. Joint 6th International Symposium on Catalysis in Multiphase Reactors/5th International Symposium on Multifunctional Reactors (CAMURE-6/ISMR-5-), 2007, Pune. 

The emphasis in this chapter is on the fruitful application of Large Eddy Simulations for reproducing the local and transient flow conditions in which these processes are carried out and on which their performance depends. In addition, examples are given of using Direct Numerical Simulations of flow and transport phenomena in small periodic boxes with the view to find out about relevant details of the local processes. Finally, substantial attention is paid throughout this chapter to the attractiveness and success of exploiting lattice-Boltzmann techniques for the more advanced CFD approaches. 

First of all, the increased computer power makes it possible to switch to transient simulations and to increase spatial resolution. One no longer has to be content with steady flow simulations on relatively coarse grids comprising 104-105 nodes. Full-scale Large Eddy Simulations (LES) on fine grids of 106—107 nodes currently belong to the possibilities and deliver realistic reproductions of transient flow and transport phenomena. Comparisons with quantitative experimental data have increased the confidence in LES. The present review stresses that this does not only apply to the hydrodynamics but relates to the physical operations and chemical processes carried out in stirred vessels as well. Examples of LES-based simulations of such operations and processes are due to Flollander et al. (2001a,b, 2003), Venneker et al. (2002), Van Vliet et al. (2005, 2006), and Flartmann et al. (2006). 

Large eddy simulations explicitly resolves the inherently unsteady character of the turbulent flow in a stirred tank into account, including the periodic phenomena associated with the motion of the impeller and their interaction with... 

Bakker, A., Oshinowo, L. M., and Marshall, E. M., The Use of Large Eddy Simulation to Study Stirred Vessel Hydrodynamics . Proceedings of the 10th European Conference on Mixing, Delft, Netherlands, 247-254 (2000). 

Derksen, J. J., and Van den Akker, H. E. A., Large eddy simulation of stirred tank flow by means of a lattice-Boltzmann scheme , In C. R. Kleijn, S. Kawano (Eds.), ASME Proceedings Volume PVP-377-2, ASME, 11-16 (1998). 

Gao, Z., Min, J., Smith J. M., and Thorpe, R. B., Large Eddy Simulation of Mixing Time in a Stirred Tank with Duals Rushton Turbines . 12th European Conference on Mixing, Bologna, Italy, pp. 431-438 (2006). 

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