Abstract
An analytical soultion of diffusion equation is obtained under arbitrary initial condition on non-steady uniform flow field. It is caluculated that concentration in a cubic cell diffuses into surrounding N cells by the rates of influence coefficients. These coefficients are determined by the analytical solution and to satisfy the mass conservation law in surrounding N cells. The presented method is explicit and absolutely stable, and is able to make highly accurate calculations for the diffusion number greater than 0.5 and the Courant number even larger than 1.
