h ( $\tau =0.25\text{e}-4$ )

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

$Rat{e}_s$

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

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

$Rat{e}_t$

1/20

7.6346e−07

—

1/75

1.2441e−05

—

1/25

3.1362e−07

3.9870

1/80

1.1296e−05

1.4955

1/30

1.5162e−07

3.9865

1/95

8.7392e−06

1.4936

1/35

8.2067e−08

3.9820

1/250

2.0529e−06

1.4971