Experimental analysis of wave deformation and bottom flow under wave-current interaction in the river mouth

A river mouth is a physically dynamic area. In this study, we analyze the hydrodynamic characteristics of this area by performing hydraulic experiments to investigate wave-current interaction by building a river mouth model in a 3-D wave basin. Using the results of these hydraulic experiments, we analyze the hydrodynamic characteristics of the region in which wave-current coexist in the river channel and the vicinity of the river mouth. We observe that, in a river channel, the turbulence flow field develops more rapidly when both waves and current are present as opposed to a situation where no current exists. This contributes to the wave energy loss, resulting in wave attenuation. This phenomenon is more obvious when the ratio between the current velocity and wave celerity, Vc/Ci increases. From the wave reflection measurements, we observe that the reflection coefficient increases as Vc/Ci increases. This causes wave attenuation in the wave-current interaction. We observe the changes in the wave heights, bottom flow, and horizontal velocity distributions in the areas where wave-current coexist in the river mouth. In particular, the measured horizontal velocity distribution shows the influence of the flow field on the combined effects of the wave and current velocity components. We observe that there is a close relationship between the wave-current interaction and sediment transport near the river mouth.