Exact and numerical solutions to a Stefan problem with two moving boundaries

The swelling of grease, grain and polymers can be modelled by a nonlinear diffusion equation with two moving boundaries, commonly called a Stefan problem. We present here numerical and exact analytical solutions for both linear and nonlinear diffusivities for a variety of parameter ranges. We examine the limitations of the usual pseudo-steady-state assumption and illustrate the interesting dynamics of this problem. (C) 2006 Elsevier Inc. All rights reserved.