A. ANSARI

N. MANGIAVACCHI

R. AKHAVAN

S. KANG

The dynamics of subgrid-scale energy transfer in turbulence is investigated in a 
database of a planar turbulent jet at 
Reλ ≈ 110, obtained by direct numerical 
simulation. In agreement with analytical predictions (Kraichnan 1976), subgrid-scale 
energy transfer is found to arise from two effects: one involving non-local interactions 
between the resolved scales and disparate subgrid scales, the other involving local 
interactions between the resolved and subgrid scales near the cutoff. The former 
gives rise to a positive, wavenumber-independent eddy-viscosity distribution in the 
spectral space, and is manifested as low-intensity, forward transfers of energy in the 
physical space. The latter gives rise to positive and negative cusps in the spectral eddy-viscosity distribution near the cutoff, and appears as intense and coherent regions of 
forward and reverse transfer of energy in the physical space. Only a narrow band of 
subgrid wavenumbers, on the order of a fraction of an octave, make the dominant 
contributions to the latter. A dynamic two-component subgrid-scale model (DTM), 
incorporating these effects, is proposed. In this model, the non-local forward transfers 
of energy are parameterized using an eddy-viscosity term, while the local interactions 
are modelled using the dynamics of the resolved scales near the cutoff. The model 
naturally accounts for backscatter and correctly predicts the breakdown of the net 
transfer into forward and reverse contributions in a priori tests. The inclusion of 
the local-interactions term in DTM significantly reduces the variability of the model 
coefficient compared to that in pure eddy-viscosity models. This eliminates the need 
for averaging the model coefficient, making DTM well-suited to computations of 
complex-geometry flows. The proposed model is evaluated in LES of transitional 
and turbulent jet and channel flows. The results show DTM provides more accurate 
predictions of the statistics, structure, and spectra than dynamic eddy-viscosity models 
and remains robust at marginal LES resolutions.</jats:p

Subgrid-scale interactions in a numerically simulated planar turbulent jet and implications for modelling

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