Non-local interactions in hydrodynamic turbulence at high Reynolds numbers: the slow emergence of scaling laws

TL;DR

This study analyzes high Reynolds number hydrodynamic turbulence through detailed simulations, revealing the emergence of scaling laws, energy transfer characteristics, and intermittency behaviors, with implications for understanding natural turbulent flows.

Contribution

It provides new insights into the spectral interactions, scaling laws, and intermittency in high Reynolds number turbulence using large-scale simulations.

Findings

Scaling laws for local and non-local interactions emerge at high Re

Energy accumulation in small scales occurs over a Reynolds-independent span

Intermittency exponents deviate from standard models at high Re

Abstract

We analyze the data stemming from a forced incompressible hydrodynamic simulation on a grid of 2048^3 regularly spaced points, with a Taylor Reynolds number of Re~1300. The forcing is given by the Taylor-Green flow, which shares similarities with the flow in several laboratory experiments, and the computation is run for ten turnover times in the turbulent steady state. At this Reynolds number the anisotropic large scale flow pattern, the inertial range, the bottleneck, and the dissipative range are clearly visible, thus providing a good test case for the study of turbulence as it appears in nature. Triadic interactions, the locality of energy fluxes, and structure functions of the velocity increments are computed. A comparison with runs at lower Reynolds numbers is performed, and shows the emergence of scaling laws for the relative amplitude of local and non-local interactions in spectral space. The scalings of the Kolmogorov constant, and of skewness and flatness of velocity increments, performed as well and are consistent with previous experimental results. Furthermore, the accumulation of energy in the small-scales associated with the bottleneck seems to occur on a span of wavenumbers that is independent of the Reynolds number, possibly ruling out an inertial range explanation for it. Finally, intermittency exponents seem to depart from standard models at high Re, leaving the interpretation of intermittency an open problem.