We propose a simple numerical method to describe the air-water gas transfer at high Schmidt number. A numerical simulation is carried out in terms of the advection-diffusion equation using interfacial velocities obtained from a direct numerical simulation of open-channel turbulent flow. The present numerical method can describe the high Schmidt number air-water gas transfer driven by turbulence dynamics of the open channel flow. The numerical results show that the surface divergence effectively promotes the interfacial gas flux. Characteristics of surface-renewal eddies, such as surface divergence and vorticities, are found on the basis of cross-correlation coefficients between the interfacial gas flux and turbulent quantities.
2016 Japan Society of Civil Engineers