LARGE EDDY SIMULATION OF MASS TRANSFER ACROSS AN AIR-WATER INTERFACE AT HIGH SCHMIDT NUMBERS

Existing subgrid-scale (SGS) models for large eddy simulation are assessed for a problem of mass transfer across an air-water interface. A special focus is laid upon a case where the Schmidt number in the liquid phase (Sc L ) is high. Dynamic Smagorinsky (DSM), dynamic mixed (DMM), and dynamic two-parameter (DTM) models are tested a priori at Sc L = 1 and 100 through comparisons with filtered direct numerical simulation (DNS) data. For both Sc L cases, the limiting behavior of Smagorinsky coefficient of the concentration field near the interface (see Fig. A1) is qualitatively well calculated by DSM. However, the serious underprediction causes poor estimation of the SGS stress and scalar flux. This is a serious issue in the high Sc L case. On the other hand, the scale-similarity type models, i.e., DMM and DTM, keep good correlation with DNS (see Fig. A2) even at the high Schmidt number. The average SGS terms and SGS dissipation rates predicted by DTM are in better agreement with DNS than DMM. However, even the SGS terms calculated by DTM are not quantitatively accurate in the high Sc L case. It is concluded that, among the three models tested, DTM predicts the SGS contribution most accurately at high Schmidt numbers, although its quantitative predictability should still be improved.