Subgrid scale models

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. 

Subgrid-scale modeling for turbulent reacting flows. Combustion and Flame 112, 593-606. 

Meneveau, C., T. S. Lund, and W. Cabot (1996). A Lagrangian dynamic subgrid-scale model of turbulence. Journal of Fluid Mechanics 319, 353-385. 

Wall, C., B. J. Boersma, and R Moin (2000). An evaluation of the assumed beta probability density function subgrid-scale model for large eddy simulation of nonpremixed, turbulent combustion with heat release. Physics of Fluids 12, 2522-2529. 

Moin, P., K. Squires, W. Cabot, and S. Lee. 1991. A dynamic subgrid-scale model for compressible turbulence and scalar transport. J. Physics Fluids 3(ll) 2746-57. 

Fureby, C. 1996. On subgrid scale modeling in large eddy simulations of compressible fluid flow. J. Physics Fluids 8 1301-11. 

In the context of LES, a new modeling issue appears for two-phase flow simulations, either in the EL or EE formulation, and is linked to the subgrid scale model for the turbulent droplet dispersion. This problem has already been addressed in [278 279[ but is still an open question. However in the case of reacting flows, turbulent droplet dispersion occurs in a very limited zone between the atomizer and the flame and it is greatly influenced by the flame dynamics, therefore limiting the impact of the subgrid scale model. 

Herring JR (1979) Subgrid Scale Modeling - An Introduction and Overview. Turb Shear Flows 1 347-352... 

Schumann U (1975) Subgrid Scale Model for Einite Difference Simulations of Turbulent Flows in Plane Channels and Annuli. J Comput Phys 18 376-404... 

Speziale, C.G. (1985). Galilean invariance of subgrid scale models in the large-eddy simulation of turbulence. Journal of Fluid Mechanics 156 55-62. 

Givi, R Filtered Density Function for Subgrid Scale Modeling of Turbulent Combustion. AIAA J. 44(1), 16-23 (2006)... 

Martin, M.R, PiomeUi, U., Candler, G.V. Subgrid-Scale Models for Compressible Large-Eddy Simulations. Theor. Comp. Fluid Dyn. 13(5), 361-376 (2000)... 

As a consequence of the 3d and time-dependent nature of buoyant flows and of the current status of development of the standard turbulence models, there is currently no way to achieve reliable results by standard models on the temperature fields in the reactor sump. The only way which is nowadays often considered to give a better solution for 3d time-dependent flows is to apply Large Eddy Simulation methods (LES). Indeed, there exist already several applications of LES to reactor typical flows for an overview see Grotzbach Worner (1999), These show the tremendous potential of the LES method and that its possibilities are going far beyond those of standard Reynolds averaged turbulence models. The main problems which need to be solved for LES methods in this context are e.g. the development of more universal subgrid scale models, of boundary conditions for buoyant flows, and of numerical methods in commercial codes that fulfill LES requirements. 

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