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ANALYSIS OF SCALAR VARIANCE MODELING FOR LARGE EDDY SIMULATION OF COMBUSTION USING EXPLICIT FILTERING

Colin R. Heye
Department of Aerospace Engineering and Engineering Mechanics The University of Texas at Austin WRW Labs. 305A, 210 East 24th Street Austin, TX 78712 USA

Colleen M. Kaul
Department of Aerospace Engineering and Engineering Mechanics, The University of Texas at Austin Austin TX, USA, 78712

Venkatramanan Raman
University of Texas at Austin, W. R. Woolrich Laboratories, 210 East 24th Street, Austin, Texas 78712-0235, USA

Abstract

Large eddy simulation (LES) of turbulent combustion requires detailed modeling subfilter scalar dissipation rate and scalar variance. Models for these quantities involve computation of gradient-based terms, which are severely contaminated by finite-difference numerical errors at scales near the filter width. To overcome this numerical issue, an explicitly filtered LES formulation for the transport of scalar moments is developed. Using scalar mixing simulations of homogeneous isotropic turbulence and turbulent jet flow configurations, the convergence of scalar statistics with increasing filter to grid ratio is investigated. In particular, the evolution of scalar variance is studied. Results in the simpler periodic flow domain show grid converged solution with filter to grid ratio of 4. Inhomogeneous flow results indicate that this ratio may be inadequate for scalar variance at certain locations, but exhibits overall convergence of filtered scalar values.