VISCOUS EFFECTS ON EVOLUTION OF STOKES WAVES.

The effects of laminar viscosity on the evolution of a steady Stokes wave train are investigated by employing a boundary-layer method. It is assumed that the nonlinearity of the second order in the wave slope, 0(ka)**2, is in the same order of magnitude as the viscous effect; i. e. , 0(ka)**2 equals 0(k delta ), where delta equals ROOT nu /2 omega equals the Stokes boundary layer thickness. A nonlinear Schroedinger equation with a dissipation term is derived as the governing equation for the wave envelope. It is shown that the viscosity not only reduces the wave amplitude but also causes a phase shift in the same order of magnitude.