Difuusselt

Difuusselt is a term used in some areas of materials science and geoscience to describe a diffusion-dominated transport process in which the boundary between different components or phases is diffuse rather than sharp. In this usage, the evolution of a transported quantity such as a solute concentration or thermal energy is governed primarily by Fickian diffusion or its generalizations, with only minor convective effects.

Mathematically, difuusselt is modeled by partial differential equations of diffusion type, possibly with nonlinear diffusivity and reaction terms. When a diffuse interface is important, phase-field or Cahn–Hilliard formulations are often used to describe the transition region.

Applications include diffusion across membranes and in porous media, transport in battery electrodes, polymer blends, and geochemical diffusion in soils and rocks.

Observationally, difuusselt profiles exhibit gradual concentration or temperature transitions across a finite thickness, with a characteristic diffusion length L ~ sqrt(D t).

Usage of the term is not standardized; it appears in a limited set of texts and may be used as a synonym for diffusion in porous media or as a descriptor for diffuse-interface diffusion, depending on the author.

See also: diffusion, diffusion equation, phase-field, Cahn–Hilliard, porous media.