Laboratory Experiments on the Hydrodynamics of Waves on Adverse Currents

A series of laboratory experiments on waves on adverse currents were conducted. The transformation of regular and irregular waves on a sloping bed was studied with and without currents. Effects of the currents on the waves transformations are reported. Concerning regular waves, wave height and wave length changes were measured. The analysis of data shows an increase of the former and decrease of the latter. Wave steepness increment, related to the case without currents, shows a clear trend proportional to the ratio between the mean current velocity and the wave celerity. For what concerns irregular waves, spectral transformation was noticed. Results show drastic changes for higher frequencies compared to the lower ones. Due to adverse currents, the frequencies higher than the peak frequency increase energy before breaking. Such transfer of energy increases when the mean current velocity increases. For adverse flow that are strong enough, waves breaking occurs and energy dissipation is concentrated on higher frequencies. Zero moment wave height changes according to the spectral transformations.