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TURBULENT SCALAR TRANSFER AND ITS DEPENDENCE ON THE SCHMIDT NUMBER

Paolo Orlandi
Department of Mechanics and Aeronautics, "Sapienza" University of Rome, Via Eudossiana 18, 00184 Rome, Italy

Robert Anthony Antonia
Discipline of Mechanical Engineering, University of Newcastle, Newcastle, 2308, NSW, AUSTRALIA

Resumo

Direct numerical simulations (DNSs) of decaying isotropic turbulence with a passive scalar at different Schmidt numbers show that the Kolmogorov and Batchelor scaling collapse the high wavenumber region of the spectra and transfer functions effectively. There is a k−1 range for the inertial-diffusive range at small Rλ for Sc ≥ 1. To gain some information at a higher Rλ, EDQNM simulations are used, after validation at small Rλ against the DNS. Although the different inertial ranges yield slopes that differ slightly from those predicted by theoretical arguments, the scaling and variation in slope between inertial and inertial-diffusive ranges are adequately reproduced by the EDQNM. The pdf of some of the terms in the transport equation for θ2 provides some insight into which term is responsible for the formation of large radius of curvature scalar gradient regions.