Diffusion in spatially and temporarily inhomogeneous media: Effects of turbulent mixing

We consider diffusion of a passive substance C in a phase-separating nonmiscible binary alloy under turbulent mixing. The substance is assumed to have different diffusion coefficients in the pure phases A and B , leading to a spatially and temporarily dependent diffusion ‘‘coefficient’’ in the diffusion equation plus convective term. In this paper we consider especially the effects of a turbulent flow field coupled to both the Cahn-Hilliard type evolution equation of the medium and the diffusion equation ~both, therefore, supplemented by a convective term!. It is shown that the formerly observed prolonged anomalous diffusion @H. Lehr, F. Sagués, and J.M. Sancho, Phys. Rev. E 54, 5028 ~1996!# is no longer seen if a flow of sufficient intensity is supplied. @S1063-651X~97!00108-6#