Evolution of unidirectional random waves in shallow water (the Korteweg - de Vries model)

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Numerical simulations of the unidirectional random waves are performed within the Korteweg -de Vries equation to investigate the statistical properties of surface gravity waves in shallow water. Nonlinear evolution shows the relaxation of the initial state to the quasi-stationary state differs from the Gaussian distribution. Significant nonlinear effects lead to the asymmetry in the wave field with bigger crests amplitudes and increasing of large wave contribution to the total distribution, what gives the rise of the amplitude probability, exceeded the Rayleigh distribution. The spectrum shifts in low frequencies with the almost uniform distribution. The obtained results of the nonlinear evolution of shallow-water waves are compared with known properties of deep-water waves in the framework of the nonlinear Schrodinger equation.