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

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

$Rat{e}_s$

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

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

$Rat{e}_t$

1/20

7.6912e−07

—

1/75

1.4774e−06

—

1/25

3.1578e−07

3.9894

1/80

1.3161e−06

1.7913

1/30

1.5251e−07

3.9919

1/90

1.0642e−06

1.8042

1/35

8.2416e−08

3.9925

1/200

2.5343e−07

1.7969