Non-stationary regimes of surface gravity wave turbulence

We present experimental results about rising and decaying gravity wave turbulence in a large laboratory flume. We consider the time evolution of the wave energy spectral components in $\omega$- and $k$-domains and demonstrate that emerging wave turbulence can be characterized by two time scales – a short dynamical scale due to nonlinear wave interactions and a longer kinetic time scale characterising formation of a stationary wave energy spectrum. In the decay regime we observed the maximum of the wave energy spectrum decreasing in time initially as the power law, $\propto t^{-1/2}$, as predicted by the weak turbulence theory, and then exponentially due to viscous friction.