Water Level type BC

In the case of level BC at the East side of the computational domain (see figure 6.1), it is necessary to modify the previously calculated (4.17) coefficient D₁, as sketched in (4.19). A₁ is not used. Here j₁ is the index of the first cell in the row inside the domain, $\eta^{BC}_{i\;j_1}$ is the specified BC level data.

Similarly, when using level BC at West side, modification (4.20) is applied over the value D_2m+1 previously calculated in (4.17). C_2m+1 is not used and the tridiagonal structure is not affected. Here j₂ is the index of the last cell of the row inside the domain, $\eta^{BC}_{i\;j_2}$ is the imposed BC level data.

$$D_1=D_1 + \frac{g \Delta t}{2 \Delta x}\eta^{BC}_{i\;j_1}$$ (7.16)

$$D_{2m+1}=D_{2m+1} - \frac{g \Delta t}{2 \Delta x}\eta^{BC}_{i\;j_2}$$ (7.17)