Unsteady-state diffusion Numerical methods

Unsteady-state diffusion often occurs in inorganic, organic, and biological solid materials. If the boundary conditions are constant with time, if they are the same on all sides or surfaces of the solid, and if the initial concentration profile is uniform throughout the solid, the methods described in Section 7.1 can be used. However, these conditions are not always fulfilled. Hence, numerical methods must be used. 

Figure 7.7-2. Concentrations for numerical method for unsteady-state diffusion. Example 7.7-1.

Numerical Method for Unsteady-State Diffusion. A solid slab 0.01 m thick has an initial uniform concentration of solute A of 1.00 kg mol/m. The diffusivity of A in the solid is = 1.0 x 10 m /s. All surfaces-of the slab are insulated except the top surface. The surface concentration is suddenly... 

Sec. 7.7 Numerical Methods for Unsteady-State Molecular Diffusion... 

---