Table 2 Numerical results for Example  1 with \(\pmb{h=2^{-8}}\) and \(\pmb{\beta =\frac{2}{3}}\)

\(\Vert u-u_{h} \Vert \)

3.21e−03

1.25e−03

5.72e−04

2.83e−04

1.00

\(\vert\!\vert\!\vert p-p_{h}\vert\!\vert\!\vert \)

1.23e−03

6.36e−04

3.21e−04

1.60e−04

1.00

\(\vert\!\vert\!\vert q-q_{h}\vert\!\vert\!\vert \)

4.12e−03

2.01e−03

1.01e−03

5.11e−04

0.98