An experimental procedure for studying soliton gases in shallow water is devised. Nonlinear waves propagate at constant depth in a 34,m-long wave flume. At one end of the flume, the waves are generated by a piston-type wave-maker. The opposite end is
a vertical wall. Wave interactions are recorded with a video system using seven side-looking cameras with a pixel resolution of 1,mm, covering 14,m of the flume. The accuracy in the detection of the water surface elevation is shown to be better than 0.1 mm. A continuous monochromatic forcing can lead to a random state such as a soliton gas. The measured wave field is separated into right- and left-propagating waves in the Radon space and solitary pulses are identified as solitons of KdV or Rayleigh types. Both weak and strong interactions of solitons are detected. These interactions induce phase shifts that constitute the seminal mechanism for disorganization and soliton gas formation.
We report on an experimental realization of a bi-directional soliton gas in a 34~m-long wave flume in shallow water regime. We take advantage of the fission of a sinusoidal wave to inject continuously solitons that propagate along the tank, back and
forth. Despite the unavoidable damping, solitons retain adiabatically their profile, while decaying. The outcome is the formation of a stationary state characterized by a dense soliton gas whose statistical properties are well described by a pure integrable dynamics. The basic ingredient in the gas, i.e. the two-soliton interaction, is studied in details and compared favourably with the analytical solutions of the Kaup-Boussinesq integrable equation. High resolution space-time measurements of the surface elevation in the wave flume provide a unique tool for studying experimentally the whole spectrum of excitations.
