Turbulence and Mixing in Deep and Coastal Oceans

摘要

The work completed under this project dealt with two aspects of turbulence andmixing in oceans. The first part of the study was devoted to experimentally investigate the nature of shear-free turbulence near a density interface sandwiched between a turbulent layer and a non-turbulent layer. The experimental results were compared with the predictions of available analytical and numerical models. The entrainment mechanisms and the fate of entrained fluid particles until they homogenize at molecular scales were also studied. These studies were extended to include turbulence on either side of the interface, including the case where there is a turbulent intensity gradient across the interface. Theoretical arguments were developed to predict the mixing rate for the latter case, with which the experimental results were compared. Finally, mean velocity shear was introduced across the interface and the resulting shear instabilities were studied systematically. In the second part of the investigation, an experiment was designed and constructed to study the nature of oscillatory boundary layers, with applications to the oceanic bottom wave boundary layer. Experiments with laminar boundary layers were completed, and studies on the turbulent case were initiated.