Time irreversibility in reversible shell models of turbulence

TL;DR

This paper investigates time irreversibility in turbulent shell models using a reversible viscous mechanism, revealing that turbulence exhibits spontaneous time-reversal symmetry breaking even without explicit dissipative terms.

Contribution

It introduces a reversible shell model to study turbulence, demonstrating that time irreversibility arises from the dynamics rather than explicit symmetry-breaking dissipation.

Findings

Time-reversal asymmetry in Lagrangian power persists in the reversible model.

Turbulent dynamics converge to a strange attractor with broken time-reversal symmetry.

Velocity structure functions show anomalous scaling, indicating inertial-range properties.

Abstract

Turbulent flows governed by the Navier-Stokes equations (NSE) generate an out-of-equilibrium time irreversible energy cascade from large to small scales. In the NSE, the energy transfer is due to the nonlinear terms that are formally symmetric under time reversal. As for the dissipative term: first it explicitly breaks time reversibility; second it produces a small-scale sink for the energy transfer that remains effective even in the limit of vanishing viscosity. As a result, it is not clear how to disentangle the time irreversibility originating from the non-equilibrium energy cascade from the explicit time-reversal symmetry breaking due to the viscous term. To this aim, in this paper we investigate the properties of the energy transfer in turbulent Shell models by using a reversible viscous mechanism, avoiding any explicit breaking of the $t \rightarrow -t$ symmetry. We probe time-irreversibility by studying the statistics of Lagrangian power, which is found to be asymmetric under time reversal also in the time-reversible model. This suggests that the turbulent dynamics converges to a strange attractor where time-reversibility is spontaneously broken and whose properties are robust for what concerns purely inertial degrees of freedoms, as verified by the anomalous scaling behavior of the velocity structure functions.