| dc.description.abstract | With increasing driving, the percolating type transition from the ordered state to the turbulent state has been observed in non-equilibrium systems, as forest fires, epidemic hydrodynamic flows, and nonlinear waves. For example, recent studies on pipe flows demonstrated that the transition from the laminar flow to turbulence is associated with the uncertain emergence, spreading, and decaying of the localized disordered flow, called turbulent puff, in the form of clusters, followed by the emergence of a large cluster percolating through the space. Similar scenario was also demonstrated in recent study on turbulent transition from ordered plane waves in nonlinear dust acoustic waves. However, the above percolating transitions were only limited to the turbulent transition from the ordered state.
Wind-driven water surface wave widely exist in nature. The large numbers of degrees of freedom of water and wind, and their complicated mutual interaction makes the wind-driven water surface wave exhibit rich spatiotemporal behaviors. However, the transition scenario from weak to strong wave turbulence and the associated waveform dynamics, especially whether the transition scenario belongs to the general class of percolating transition found in previous studies on non-equilibrium systems remain elusive.
In this work, the above unexplored issues are experimentally investigated in a shallow water wave system driven by steady wind. The spatiotemporal wave height evolution can be directly monitored through diffusion light photography. Hot and cold turbulent sites (HTSs and CTSs, respectively) in the 1+1D spatiotemporal (yt) space are identified through wavelet transform. Here, y is normal to the wave propagation direction. It is found that, with increasing fetch (x, the distance from the wind entrance), the transition from the weakly turbulent state to the strong turbulent state is associated with the sporadic emergence of HTSs in the form of clusters following power-law cluster size distribution in the yt space, followed by the formation of a large HTSs cluster percolating through the yt space. The quiescent space and quiescent time between two neighboring clusters also exhibit stretched exponential distributions. The scaling exponents around the transition point are also similar to those found in the model and experimental studies of direct percolating transition in hydrodynamic flows. | en_US |