Modeling Streamflow-Driven Gas-Liquid Transfer Rate

Abstract

A streamflow-driven gas-liquid transfer rate model was developed. This model was developed in terms of total surface renewal rate and gas diffusion coefficient. The total surface renewal rate was considered to be the sum of the surface renewal rates caused by the turbulence from the air-water interface and that from the water-bed interface. A general mixing length formula and a vertical fluctuation velocity formula was developed to formulate the surface renewal rate. Predictions of this model show good agreements with the measurements in previous studies and the predictions of Churchill's, O'Connor-Dobbins', and Owens-Gibbs' formulae. It was indicated in some previous studies that the existing streamflow-driven gas-liquid transfer rate formulae have limited application ranges. The model developed in this study can be applied for all the normal ranges of flow velocity and water depth in natural rivers, which generalizes and simplifies the applications.