MacCormack method


In computational fluid dynamics, the MacCormack method is a widely used discretization scheme for the numerical solution of hyperbolic partial differential equations. This second-order finite difference method was introduced by Robert W. MacCormack in 1969. The MacCormack method is elegant and easy to understand and program.

The algorithm

The MacCormack method is a variation of the two-step Lax–Wendroff scheme but is much simpler in application. To illustrate the algorithm, consider the following first order hyperbolic equation
The application of MacCormack method to the above equation proceeds in two steps; a predictor step which is followed by a corrector step.
Predictor step: In the predictor step, a "provisional" value of at time level is estimated as follows
The above equation is obtained by replacing the spatial and temporal derivatives in the previous first order hyperbolic equation using forward differences.
Corrector step: In the corrector step, the predicted value is corrected according to the equation
Note that the corrector step uses backward finite difference approximations for spatial derivative. The time-step used in the corrector step is in contrast to the used in the predictor step.
Replacing the term by the temporal average
to obtain the corrector step as

Some remarks

The MacCormack method is well suited for nonlinear equations The order of differencing can be reversed for the time step. For nonlinear equations, this procedure provides the best results. For linear equations, the MacCormack scheme is equivalent to the Lax–Wendroff method.
Unlike first-order upwind scheme, the MacCormack does not introduce diffusive errors in the solution. However, it is known to introduce dispersive errors in the region where the gradient is high.