Title: Turbulent Schmidt numbers for CFD simulations using the k-ε and k-ω models

Authors: Manuel Martínez; Jordi Pallarès; Anton Vernet

Addresses: Department of Mechanical Engineering, Universitat Rovira i Virgili, Av. Països Catalans 26, 43007, Tarragona, Spain ' Department of Mechanical Engineering, Universitat Rovira i Virgili, Av. Països Catalans 26, 43007, Tarragona, Spain ' Department of Mechanical Engineering, Universitat Rovira i Virgili, Av. Països Catalans 26, 43007, Tarragona, Spain

Abstract: Turbulent diffusion dominates mixing at high molecular Schmidt numbers. When solving the Reynolds averaged Navier-Stokes equations, one of the key parameters for the correct simulation of mixing is the turbulent Schmidt number (Sct). In the case of the k-ε turbulence model, many CFD packages suggest a value of 0.7 for Sct. However, it has been demonstrated that this value is not adequate for all cases. This paper reports simulations for three different cases of turbulent mixing and compares the results with experimental data. It has been found that, for jets in crossflow, Sct is a function of the Reynolds number of the jet, the ratio between the diameters of the jet and main flow and the turbulent intensity of the jet and the main flow. Numerical simulations using the k-ω model are also performed, showing that the required value of Sct is dependent on the turbulence model used.

Keywords: turbulent Schmidt numbers; computational fluid dynamics; CFD; numerical simulation; jets; crossflow; turbulent mixing; k-epsilon model; k-omega model; turbulent diffusion; turbulence modelling; Reynolds averaged Navier-Stokes; RANS equations.

DOI: 10.1504/PCFD.2016.080056

Progress in Computational Fluid Dynamics, An International Journal, 2016 Vol.16 No.6, pp.356 - 363

Received: 08 Nov 2014
Accepted: 01 Oct 2015

Published online: 28 Oct 2016 *

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