Formation of Large-Amplitude Low-Frequency Waves in Capillary Turbulence   on Superfluid He-II
  The results of experimental and theoretical studies of the parametric decay instability of capillary waves on the surface of superfluid helium He-II are reported. It is demonstrated that in a system of turbulent capillary waves low-frequency waves are generated along with the direct Kolmogorov-Zakharov cascade of capillary turbulence. The effects of low-frequency damping and the discreteness of the wave spectrum are discussed. 
Leonid V. Abdurakhimov, German V. Kolmakov, Aleksander A. Levchenko,   Yuri V. Lvov, and Igor A. Remizov
physics.flu-dyn cond-mat.stat-mech nlin.CD