| $ \xi_1$ | $ \Delta x_1 (1-2y^{n}-\Delta y \frac{\Delta x_1}{\Delta x}) $ | $ (0.5-x^n)(0.5-y^n) $ | $ (0.5-x^n)(0.5-y^n) $ |
| $ \xi_2$ | $ \Delta x_1 \Delta y {\Delta x_1}/ (\Delta x)$ | $ (0.5-x^n)(0.5-y^n) $ | $ (0.5-x^n)(0.5-y^n) $ |
| $ \xi_3$ | $ [\Delta y (2-\Delta x_1)\frac{\Delta x_1}{\Delta x} + (2-\Delta x \frac{\Delta y_2}{\Delta y})(0.5-y^{n}-\Delta y \frac{\Delta x_1}{\Delta x})] $ | $ (2+x^n-x^{n+1})(0.5-y^n)$ | $ (1.5+x^n)(0.5-y^n)$ |
| $ \xi_4$ | $ \Delta x_1 (1+2y^{n}+\Delta y \frac{\Delta x_1}{\Delta x}) $ | $ (0.5-x^{n})(2+y^{n}-y^{n+1}) $ | $ (0.5-x^n)(1.5+y^n) $ |
| $ \xi_5$ | $ \Delta x_2 (0.5-y^{n}-\Delta y \frac{\Delta x_1}{\Delta x}) $ | $ (x^{n+1}-0.5)(0.5-y^{n}) $ | $ 0 $ |
| $ \xi_6$ | $ \Delta x \frac{\Delta y_2}{\Delta y}(0.5-y^{n}-\Delta y \frac{\Delta x_1}{\Delta x}) $ | $ (x^{n+1}-0.5)(0.5-y^{n}) $ | $ 0 $ |
| $ \xi_7$ | $ [\Delta x_2 (1.5+y^{n}+\Delta y \frac{\Delta x_1}{\Delta x}) + (x^{n+1}-0.5-\Delta x \frac{\Delta y_2}{\Delta y})(2.5-y^{n+1})] $ | $ (x^{n+1}-0.5)(2+y^{n}-y^{n+1}) $ | $ (x^{n+1}-0.5)(2.5-y^{n+1}) $ |
| $ \xi_8$ | $ (y^{n+1}-0.5) (2.5-\Delta x \frac{\Delta y_2}{\Delta y}-x^{n+1}) $ | $ (2+x^{n}-x^{n+1})(y^{n+1}-0.5) $ | $ (2.5-x^{n+1})(y^{n+1}-0.5)$ |
| $ \xi_9$ | $ (y^{n+1}-0.5) (-0.5+\Delta x \frac{\Delta y_2}{\Delta y}+x^{n+1}) $ | $ (x^{n+1}-0.5)(y^{n+1}-0.5) $ | $ (x^{n+1}-0.5)(y^{n+1}-0.5) $ |
| $ \xi_{10}$ | $ (y^{n+1}-0.5) (-0.5-\Delta x \frac{\Delta y_2}{\Delta y}+x^{n+1}) $ | $ (x^{n+1}-0.5)(y^{n+1}-0.5) $ | $ (x^{n+1}-0.5)(y^{n+1}-0.5) $ |
| $ \xi_{11}$ | $ 0 $ | $ (0.5-x^{n})(y^{n+1}-0.5) $ | $ 0 $ |
| $ \xi_{12}$ | $ 0 $ | $ (0.5-x^{n})(y^{n+1}-0.5) $ | $ 0 $ |
| 其中: $\Delta x = x^{n+1}-x^{n}$, $\Delta y = y^{n+1}-y^{n}$, $\Delta x_1 = 0.5-x^{n}$, $\Delta y_1 = \Delta y {\Delta x_1}/{\Delta x}, $ |
| $x_{M_1} = 0.5$, $y_{M_1} = y^{n}+\Delta y_1$, $\Delta y_2 = 0.5-y_{M_1}$, $\Delta x_2 = \Delta x {\Delta y_2}/{\Delta y}.$ |