Transition to turbulence behind a traveling plate

Abstract

The Lyapunov field measures the sensitivity to small perturbations of the fluctuating flow behind an accelerated plate. Using a robot, we repeat this experiment 42 times and measure the difference between the flows as they turn turbulent. The Lyapunov field of a single experiment (left) mirrors the (logarithmic) difference between its 42 repetitions (right). It is an expression of ergodicity, and a vivid illustration of the butterfly effect.