Scalar-energy spectra in simulations of Sc⪢1 mixing by turbulent jets using the nonlinear large-eddy simulation method

The nonlinear large-eddy simulation (nLES) method is applied to the first numerical study of passive-scalar mixing by a turbulent shear flow at a high Schmidt number (Sc⪢1). The work is intended to address inconsistencies between previous studies concerning the formation of power-law scaling in the scalar-energy spectra at viscous-convective scales. Results are reported for LES of a round turbulent jet at Sc=1024 and ReD=2000. The nLES method is first shown to recover the large-scale jet structure, including the self-similarity of far-field scalar moments. Scalar timeseries and spatial data produce the first power spectra from a LES shear-flow study that exhibits k−1 scaling at viscous-convective scales, consistent with the analysis of Batchelor [J. Fluid Mech. 5, 113 (1959)] and recent direct numerical studies of simpler Sc⪢1 flows.

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