Abstract
Direct numerical simulations for thermally-stratified open-channel flows are carried out to investigate the effects of stratification on free-surface turbulence and heat/mass transfer at the water surface. The numerical results show that the surface velocity divergence and the heat flux vary clearly depending on stable and unstable stratified conditions. The dependence of characteristic quantities such as the surface divergence and the surface mean velocity on the Richardson number is revealed from the present numerical results. Also, the numerical results suggest that the behavior of scalar transfer velocity from an empirical relation proposed by Sanjou and Nezu (2013) doesn’t depend on the Richardson number, so that their relation may be effective even in thermally-stratified open-channel flows under stable and unstable stratified conditions.
