As (5.13) is normally not diagonal-dominant it is eliminated in a pre-pass. It is important to note, that in this case the structure of the equation system changes. The constitutive relation for is now given by (5.13) whereas for by (5.14), or vice-versa. This is accomplished by the following transformation matrix

t_{x, y} |
||

1 | 1 |

The fluxes contained in
*f*_{} can also be used to calculate
the total interface flux *F*_{I} by setting up the following equation:

f_{} = f^{S}_{} + F_{I} = 0 |
(5.15) |

with *i* running over all interface points.

1999-05-31