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HIGH-SPEED TURBULENT MIXING AND COMBUSTION: MILES VS PHYSICAL LES

Mehmet Karaca
ICARE-CNRS 1c, ave. de la Recherche Scientifique F-45071 Orleans cedex 2, France

Ivan Fedioun
ICARE-CNRS 1C avenue de la Recherche Scientifique, F-45071 Orleans cedex 2, France

Nicolas Lardjane
L.C.S.R./E.P.E.E. - C.N.R.S. 1c, avenue de la Recherche Scientifique 45071 Orleans cedex 2, France; CEA-DAM-DIF F-91297 Arpajon, France

Аннотация

This work reports a numerical experiment designed to address the 4th and 9th questions posed by S.B. Pope (New Journal of Physics, 2004) concerning the respective merits of physical and numerical (or implicit) Large Eddy Simulation (LES and MILES), in the simulation of high speed non-reacting and reacting air/H2 jets 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 subgrid models associated to molecular diffusion. Implicit LES are performed with and without molecular diffusion. In the non-reacting case, the Smagorinsky model is too dissipative, even with a low value of the constant, Cs = 0.1. The Selective Structure Function leads to better results, but does not show any superiority compared to MILES, 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 MILES-Euler, hence to achieve grid-convergence.