Amplitude phase coupling of multi-scale coherent excitations in wind-driven water wave turbulence
Wei-Shuo Lo1*, Ji-Lin Jou1, Lin I1
1Department of Physics, National Central University, Jhongli, Taiwan
* Presenter:Wei-Shuo Lo,
Under strong wind, wave turbulence over a wide range of spatiotemporal scales can be excited on the water surface, which makes the water surface wave turbulence an interesting platform to explore the interesting spatiotemporal dynamical behavior through direct visualization. In this work, the coupling of multi-scale coherent excitations in the wind-driven water wave turbulence is experimentally investigated. Using diffusive light photography, wave height evolution in the 2+1D space-time space is measured. It is found that under strong wind, the turbulence exhibits intermittent large and small amplitude extreme events. The turbulence has a continuous power spectrum with two major bumps. Through empirical mode decomposition, the wave height evolution is decomposed into modes with different scales. The cascaded amplitude modulations of the shorter wavelength modes by the phases of the longer wavelength modes are observed. It might be caused by the more effective energy input for exciting the shorter wavelength modes in the windward side than that of the leeward side of the longer wavelength mode. The synchronization of the crests of all modes leads to the emergence of giant peaks in the turbulence.

Keywords: wind wave, wave turbulence, mode-mode coupling