Spatiotemporal intermittency and chaotic saddles in the regularized long-wave equation

Transition to intermittent spatiotemporal chaos is studied in the regularized long-wave equation, a nonlinear model of shallow water waves. A mechanism for the onset of on-off spatiotemporal intermittency is explored. In this mechanism, the coupling of two chaotic saddles triggers random switching between phases of laminar and bursty behaviors. The average time between bursts as a function of the control parameter follows a power law typical of crisis transitions in chaotic systems. The degree of spatiotemporal disorder in the observed fluid patterns is quantified by means of the time-averaged spectral entropy for both chaotic attractors and chaotic saddles. The implications of these results to other fluid systems are discussed.