Influence of Small Water Surface Perturbations on the Reaeration Process

This paper aims to develop a general reaeration model for water bodies subject to small surface perturbation, such as ripples that may be induced by wind, waves, and surface current. A test rig was specially designed and fabricated to study the influence of waves on the reaeration process. The wave frequency varied from 0.125Hz to 0.425Hz for various wave heights, H, ranging from 0.15cm to 1.5cm. Based on the findings of the experimental study, the authors developed a modified film model and introduced a diffusive film-layer thickness delta D as the characteristic length scale for the reaeration process. The thickness of the diffusive film layer may be determined readily in one of two ways: (1)as the ratio between the molecular diffusivity of dissolved oxygen and the measured oxygen transfer coefficient; and (2)estimated using its established functions with other concentration boundary layers proposed by various researchers. The modified film model was found to unify the present experimental data and published data.