Velocity and pressure measurements in the turbulent boundary layer above mechanically generated water waves

The structure of the pressure and velocity fields in the air above mechanically generated water waves was investigated in order to evaluate their contribution in the transfer of momentum and energy from wind to water waves. The nonlinearities of the propagating water wave and the drift current seem to introduce pressure components at frequencies other than that of the main wave. Wave-wave resonant interactions and wave-turbulence nonlinear interactions are also responsible for the strong wave induced pressure harmonics. The momentum and energy transfer rates supported by the waves were found to be dominated by the wave induced pressure, but the transfer of the corresponding total quantities to both waves and currents may or may not. The contribution of the wave induced Reynolds stresses to the transfer processes is negligible. The momentum and energy partition between waves and currents is sensitive to the wind field. The water surface condition varies between the transition region and the fully rough regime. At high wind speeds the water surface becomes aerodynamically rough.