h ( $\tau =0.015\text{e}-4$ )

${\Vert u^N-u_h^N\Vert }_{0,h}$

$Rat{e}_s$

$\tau$ ( $h=0.5\text{e}-4$ )

${\Vert u^N-u_h^N\Vert }_{0,h}$

$Rat{e}_t$

1/20

1.1895e−05

—

1/75

7.6119e−05

—

1/25

2.3858e−06

3.9624

1/80

7.0473e−05

1.1941

1/30

7.6174e−07

3.9685

1/95

5.7340e−05

1.2001

1/35

3.1550e−07

3.9502

1/250

1.7946e−05

1.2005