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 = 2 up to Sc = 500, it was found that KL ∝ Sc²/³, which is in agreement with predictions based on solid-liquid transport models, see e.g. Davies (Turbulence Phenomena 1972). For similar RT , the transfer velocity was observed to reduce significantly compared to 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. (Int. J. Heat Mass Transfer, 1976), the normalised KL in the present no-slip case was also found to depend on RT ‾¹/² and RT ‾¹/⁴ for small and large turbulent Reynolds numbers, respectively.