Abstract
A spectral large-eddy simulation of the velocity and passive temperature fields in three-dimensional isotropic turbulence is developed at high Reynolds numbers and a Prandtl number of the order of 1. The temperature spectrum in the large scales is shown to develop a range of the form ET(k)≈0.1η[〈u2〉/ε]k−1, where ε and η are the kinetic energy and temperature variance dissipation rates, respectively. This range, which is a result of shearing by large scale velocity gradients, is followed by a k−5/3 inertial-convective range at higher wavenumbers. The temperature variance decays much faster in time than the kinetic energy. Finally, the spectral eddy conductivity rises logarithmically with k toward small wavenumbers, contrary to the eddy viscosity that displays a plateau.
Published Version
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