Contribution to the development of implicit large eddy simulations methods for compressible turbulent flows

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2012
Karaca, Mehmet
This work is intended to compare Large Eddy Simulation and Implicit Large Eddy Simulation (LES and ILES) for a turbulent, non-reacting or reacting high speed H2 jet in co-flowing air, typical of scramjet engines. Numerical simulations are performed at resolutions ranging from 32×32×128 to 256×256×1024, using a 5th order WENO scheme. Physical LES are carried out with the Smagorinsky and the Selective Structure Function models associated to molecular diffusion. Implicit LES are performed with and without molecular diffusion, by solving either the Navier-Stokes or the Euler equations. In the nonreacting case, the Smagorinsky model is too dissipative. The Selective Structure Function leads to better results, but does not show any superiority compared to ILES, whatever the grid resolution. In the reacting case, a molecular viscous cut-off in the simulation is mandatory to set a physical width for the reaction zone in the ILES approach, hence to achieve grid-convergence. It is also found that ILES/LES are less sensitive to the inlet conditions than the RANS approach. The first chapter is an introduction to the context of this study. In the second chapter, the governing equations for multispecies reacting flows are presented, with emphasis on the thermodynamic and transport models. In the third chapter, physical LES equations and explicit sub-grid modeling strategies iv are detailed. Some properties of the numerical scheme are also investigated. In chapter four, the numerical scheme and some aspects of the solver are explained. Finally, non-reacting and reacting numerical experiments are presented and the results are discussed.

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Citation Formats
M. Karaca, “Contribution to the development of implicit large eddy simulations methods for compressible turbulent flows,” Ph.D. - Doctoral Program, Middle East Technical University, 2012.