SINOPSIS

A series of numerical simulation is carried out of high Schmidt number turbulent mass transfer across interfaces of different dynamical conditions, i.e., a clean or contaminated free surface and also a solid surface. With increasing the Marangoni number representing the surface tension effect, low-frequency fluctuations of surface divergence, which play a critical role in the interfacial mass transfer, are drastically decreased. Various statistics of the turbulent concentration fluctuation reveal that the transport mechanism at a contaminated interface becomes dynamically equivalent to that at a solid surface beyond a critical Marangoni number. Consequently, the interfacial gas transfer rate falls down to that on a solid surface, so that the Schmidt number exponent switches from −0.5 to −0.7. Based on a one-dimensional advection-diffusion equation, a criterion for the transition of the turbulent mass transfer mode is discussed.