In tills article, we develop a two-dimensional finite-difference scheme for
solving the convection-diffusion equation. The numerical method involves u
sing transformation on the prototype scalar transport equation and transfer
ring it to a Helmholtz equation. We apply the alternating-direction implici
t scheme of Polezhaev to solve for the Helmholtz equation. As the key to su
ccess ill simulating the convection-diffusion equation, we exploit the solu
tion pertaining to the Helmholtz Equation in the coal se of scheme developm
ent, thereby providing high-level accuracy to the prediction. Since this is
a new method developed for solving the model equation, it is illuminating
to conduct modified equation analysis on the discrete equation in order to
make a fall assessment of the proposed method. The results provide us with
useful insights into the nature of the scheme, It is standard practice to v
alidate the cone by investigating test problems which ale amenable to exact
solutions to tbe working equation. Results show exact agreement for the on
e-dimensional test problem and good agreement with the analytic solutions f
or two-dimensional problems.