OBSERVATIONS ON ERROR IN THE APPLICATION OF THE FORWARD-DIFFERENCE METHOD TO THE BULK DIFFUSION EQUATION

The Forward-Difference Method was applied to the one-dimensional diffu sion equation for a problem with constant surface and initial solute c oncentrations and diffusivity independent of concentration. Two intere sting observations were made on the error between the exact analytic s olution and the numerical solution: (1) when x equals root 2Dt, the Fo rward-Difference Method becomes very accurate no matter what value of lambda (= D Delta t/Delta x(2)) was used; (2) the maximum error, which occurs at similar to 2.76 root Dt, increased linearly with lambda.