2021 年 77 巻 2 号 p. I_967-I_972
The wind stress acting on the water surface and the thermal stratification are typical factors changing turbulent flows and material transfers in natural water-environments. In this study, we analyze numerically how these two factors affect turbulence properties and the heat transport flux at the water surface in a turbulent open-channel flow by means of the direct numerical simulation (DNS). Under the stable, neutral and unstable stratification conditions, the open-channel flow with the surface shear stress is simulated, and the surface divergence and the heat transport flux are obtained from the numerical data. The numerical results demonstrate that the surface divergence can be universally described with the Taylor micro scale even in the presence of the combined effects of the two factors. The standard surface divergence model is confirmed to be approximately applied for the turbulent open-channel flow driven by the surface shear stress and the thermal stratification, but the proportional coefficient of the divergence model varies complicatedly with the surface shear stress, depending on the Richardson number.
