Intermittent fluctuations determine the nature of chaos in turbulence

We adapt recent ideas for many-body chaos in nonlinear, Hamiltonian fluids [Murugan et al., Phys. Rev. Lett. 127, 124501 (2021)] to revisit the question of the Reynolds number Re dependence of the Lyapunov exponent λ∝ Re^α in fully developed turbulence. The use of such decorrelators allow us to investigate the interplay of the competing effects of viscous dissipation and nonlinearity. We obtain a precise value of α = 0.59 ± 0.04 and show that departure from the Kolmogorov mean field result λ ∝ √ Re is a consequence of the intermittent fluctuations in the velocity-gradient tensor. The robustness of our results are further confirmed in a local, dynamical systems model for turbulence.