Passive particles Lévy walk through turbulence mirroring the diving patterns of marine predators

Lagrangian stochastic models for the simulation particle trajectories in turbulent flows can be made to be consistent with Kolmogorov's similarity theory and with prescribed Eulerian velocity statistics. Intermittency (i.e., large temporal fluctuations in the rate of dissipation of turbulent kinetic energy) can also be accounted for but is usually neglected because its impact on turbulent dispersion is typically negligible. Here I show both heuristically and with the aid of numerical simulations that intermittency results in Lévy (Cauchy) walk movement patterns. The novel predictions finds strong support in an analysis of movement pattern data for inert (dead) copepods in turbulent flows. This is the first experimental account of single particle movements in turbulence having Lévy walk characteristics. The mechanism stands apart from the much-studied chaotic and multiplicative pathways to Lévy walking. Lévy walk have been observed in sharks, bony fishes and in other aquatic marine predators and these have been attributed to the execution of an evolved, advantageous searching strategy. The new finding suggests that going with the flow is sufficient to explain the occurrence of these Lévy walks. (paper)