On turbulent mass transfer near a liquid—fluid interface

Abstract

The main contributions of the paper are: 1. 1. A renewal model is proposed in which one considers that the elements of liquid in contact with the interface have a micro hydrodynamic structure and are not ‘solid’ as in Danckwerts' theory. Instead of Higbie's penetration theory, the generalised penetration theory proposed by the author is used for obtaining information concerning the rate of mass transfer in each element of liquid. 2. 2. Arguments are adduced in support of a roll cell model superposed on the average motion. By using a time dependent velocity distribution compatible with such a description and solving the time dependent convective—diffusion equation, one obtains for the mass transfer coefficient an expression similar to that obtained by means of the renewal model. The renewal assumption is no longer made, but is a result of the assumed velocity distribution. 3. 3. A deterministic approach of turbulent mass transfer, by using for the time dependent velocity distribution almost periodical functions, is proposed. The approach is suggested by the fact that such types of functions have the disordered feature of turbulent fluctuations. The similarity between such a treatment and the statistical one (based on the distribution of times of contact with the interface) is stressed.