Influence of Waves on Air‐Water Gas Transfer

Abstract

Experiments on air‐water gas transfer were performed in a flume with a mechanical wave maker for the determination of the gas‐transfer coefficient with waves. Oxygen was used as the transferred gas. The experiments indicate that nonbreaking deep‐water gravity waves significantly influence air‐water gas transfer. The gas‐transfer coefficient was correlated with the wave characteristics. A renewal model was used for the analysis of the data, and the renewal rate was dependent on a wave Reynolds number. The gas‐transfer coefficient was linearly dependent upon the product of wave height and wave frequency. This is also equivalent to the gas‐transfer coefficient being directly proportional to the wave velocity at the water surface. Comparison with data reported in the literature indicates that a significant portion of the observed gas transfer in wind‐wave flume experiments can be attributed to nonbreaking waves. The presence of bubbles or bubble‐entraining breaking waves enhances the gas‐transfer coefficient considerably. Visual correlation between breaking intensity and the transfer coefficient was good, although the relation has not been quantified.