ARTICLE:

• Effects of Interfacial Velocity Boundary Condition on Turbulent Mass Transfer at High Schmidt Numbers  download article

Y. Hasegawa
Department of Mechanical Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

N. Kasagi
Department of Mechanical Engineering, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan

ABSTRACT

Numerical simulation of high Schmidt number turbulent mass transfer across free and solid surfaces is carried out. Near the free surface, the concentration field quickly responses to the normal velocity fluctuation and the eddy diffusivity is almost unchanged at a wide range of the Schmidt number. Whereas, near the solid wall, the concentration field becomes more insensitive to the normal velocity fluctuation and the eddy diffusivity is drastically decreased with increasing the Schmidt number. This fundamental difference between the concentration field close to the free and solid surfaces can be attributed to the difference of the spatial variation of the normal velocity fluctuation, namely, the normal velocity varies linearly with the distance from the free surface, while quadratically near the solid surface. The strong damping of the high-frequency concentration fluctuation near the solid surface agrees fairly well with the theoretical analysis by Shaw and Hanratty. These results indicate that the classical approach, which assumes the analogy between momentum and mass transfer near the solid wall, can not be used at the high Schmidt numbers.

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