Energy backscatter in large-eddy simulations of three-dimensional incompressible isotropic turbulence

ISSN： 1468-5248

Source： Journal of Turbulence, Vol.1, Iss.1, 2000-01, pp. : 10-10

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Abstract

The issue of energy backscatter in decaying three-dimensional incompressible isotropic turbulence is studied by means of large-eddy simulations (LES). For each set of initial parameters, multiple realizations are performed to improve the statistical convergence of the infrared modes. For an initial energy spectrum E(k, 0) k^s0 as k 0 with s₀ = 4, LES display a non-negligible k⁴ energy backscatter at subsequent times: E(k,t)t⁴k⁴. The value of ₄, superior to the 0.16 eddy-damped quasi-normal Markovian(EDQNM) value, depends upon the resolution of the simulation and the integration time. In the LES initialized with s₀ = 3.5, a weak energy growth is observed at small wavenumbers. However, the infrared energy spectrum does not develop the k⁴ component predicted by Eyink and Thomson (2000 Phys. Fluids12 477-9). With s₀ = 3, on the other hand, an almost perfect invariance of the infrared energy spectrum is observed. Attention is also paid to the energy decay laws. For s₀ = 4, energy decays as t^-1.4 in the 256³ LES, which is intermediate between the EDQNM t^-1.38 law and Kolmogorov's t^-10/7t^-1.43prediction. For s₀ = 3.5 and s₀ = 3, the LES energy decay law is also compared with the theoretical predictions based upon self-similarity.