A surface wave instability on liquid helium and water Free

Nonlinear systems tend to display increasingly more complicated behavior as they are driven harder and harder. In such an experiment presented here, surface waves are parametrically generated when a trough, partially filled with liquid $He4$ or water, oscillates vertically. These waves become modulated at independent frequencies that appear one by one, and that may or may not phase lock on each other, as the drive amplitude is further increased. The modulations are the result of energy flowing into the lowest modes of the trough, despite the modes' response being unsynchronized to the drive. [Work supported by ONR.]