Experimental study on characteristics of turbulence and sediment transport produced by wind-induced water waves

Abstract

Many researchers and engineers have shown great interest in mass transfer processes produced by wind-induced waves. Such waves contribute significantly to the transfer of environmental materials, such as sediment and marine debris, and the turbulence occurring beneath the waves further complicates wave-induced mass transport. The phase cycle of wave motion is generally considered to be a key determinant of mean flow and turbulence. In aqueous environmental engineering, this relationship is a crucial one to investigate, since turbulence is closely related to mass transport. To address this question, we measured the time-series of instantaneous velocity vectors by means of particle image velocimetry in a laboratory flume to reveal the turbulence structure induced by wave motion. By using a wavelet analysis free of specific assumptions, we were able to decompose the instantaneous velocity data into mean current, wave motion, and turbulence components. This analysis allowed for the objective evaluation of the shear stresses related to wave energy and turbulence energy production. Furthermore, we found significant phase characteristics of energy transfer among mean velocity, wave, and turbulence components. In order to examine the diffusion and convection properties induced by wind waves, we also conducted tracking analysis of imaginary sediment markers. Our results support the conclusion that mass transfer induced by wind waves impacts the entire range of water depths, at least in relatively shallow aqueous environments.