A review of the turbulent mixing by wind wave breaking

Abstract

It is formidable task to provide a comprehensive investigation of wave breaking and its turbulence process. In this review paper, the observations of turbulence by wave breaking and its parameterizations since 1990 are presented. Among them, the following are the most important. (1)Wave breaking induced turbulent mixing process cannot be described by the wall-layer theory, that is, the rate of dissipation of turbulent kinetic energy is not proportional to the inverse of water depth. In fact, a significant turbulent mixing enhancement in near-surface layer for a depth of several meters is achived by wave breaking. The dissipation rate of turbulence kinet energy is one to three orders larger than the value predicted by the wall-layer scaling. (2)In the crest region above the mean waterline, the dissipation rate increases as disz-2.3, while in the region below the trough, the dissipation rate decreases as disexp(-z) or disz-2. (3)The turbulent mixing length is a critical physical quantity to study the wave breaking. Up to now, however, there has been a large difference between the values given by the previous studies. Extensive work on the mixing depth and turbulent mixing length by wave breaking is also needed in the future.