Isotropic-turbulence-induced mass transfer across a severely contaminated water surface

Abstract

Direct numerical simulations were performed to investigate the effect of severe contamination on interfacial gas transfer in the presence of isotropic turbulence diffusing from below. A no-slip boundary condition was employed at the interface to model the severe contamination effect. The influence of both Schmidt number (Sc) and turbulent Reynolds number (RT ) on the transfer velocity (KL) was studied. In the range from Sc D 2 up to Sc D 500 it was found that KL∝ Sc-2/3, which is in agreement with predictions based on solid-liquid transport models, see e.g. Davies (1972, Turbulence Phenomena, Academic). For similar RT, the transfer velocity was observed to reduce significantly compared with the free-slip conditions. The reduction becomes more pronounced with increasing Schmidt number. Similar to the observation for free-slip conditions made by Theofanous et al. (Intl J. Heat Mass Transfer, vol. 19 (6), 1976, pp. 613-624), the normalized KL in the present no-slip case was also found to depend on RT-1/2 T and RT-1/4 T for small and large turbulent Reynolds numbers, respectively.