APPROXIMATION OF SUBGRID-SCALE ENERGY-TRANSFER BASED ON THE DYNAMICS OF RESOLVED SCALES OF TURBULENCE

Previously established properties of subgrid-scale nonlinear interactions in turbulent hows at low Reynolds numbers are employed to approximate the subgrid-scale energy transfer in terms of the resolved scales for statistically stationary channel flow. The approximation is obtained by focusing on the dynamics of resolved scales in the vicinity of the cutoff wave number. Predicted plane-averaged transfer is in a good agreement with the exactly computed quantity. The modeled forward transfer and inverse transfer are comparable, similarly to the case of the exact transfer, but each is overestimated by the model. The exact and the modeled transfers exhibit only moderate pointwise correlation, which increases if conditional probabilities of forward and inverse transfers are considered. Probability distribution functions for modeled and exact transfers are in a good qualitative agreement. In all cases the results provided by the approximation are at least comparable to, and generally better than those provided by the classical Smagorinsky model. (C) 1995 American Institute of Physics.