Modeling Unsteady-state Diffusion with Concentration-dependent Diffusivity through a Anisotropic Medium

This paper discusses the modeling of unsteady-state mass diffusion under concentrationdependent diffusivity through an orthotropic medium. Historically, a simpler one-dimensional formulation with constant medium properties has been used, leading to approximate solutions. The present work uses a finite element formulation with finite difference discretization in time. The code includes an element-reference vector of diffusivities; the vector is updated after each time-step, using the average of all nodal concentration values within the element and a model for the concentration dependency. The paper discusses comparative results with experimental values for the case of moisture diffusion through Norway spruce (picea abies). The proposed model allows a better fit to experimental results.