Relations involving span-wise velocity

Differentiations

\[\sumzf \sumyc \sumxc \vel{3} \dif{q}{\gcs{1}} = - \sumzf \sumyc \sumxf \dif{\vel{3}}{\gcs{1}} q,\]

where \(\vat{\vel{3}}{\frac{1}{2},\ccindex{j},\cpindex{k}} = \vat{\vel{3}}{\ngp{1} + \frac{1}{2},\ccindex{j},\cpindex{k}} = 0\) is assumed (i.e., the walls do not move in the \(z\) direction).

\[\sumzf \sumyc \sumxc \vel{3} \dif{q}{\gcs{2}} = - \sumzf \sumyf \sumxc \dif{\vel{3}}{\gcs{2}} q.\]
\[\sumzf \sumyc \sumxc \vel{3} \dif{q}{\gcs{3}} = - \sumzc \sumyc \sumxc \dif{\vel{3}}{\gcs{3}} q.\]

Averages

\[\sumzf \sumyc \sumxc \vel{3} \ave{q}{\gcs{1}} = \sumzf \sumyc \left( \vat{\vel{3}}{1} \frac{\vat{q}{\frac{1}{2}}}{2} + \sum_{i = \frac{3}{2}}^{\ngp{1} - \frac{1}{2}} \ave{\vel{3}}{\gcs{1}} q + \vat{\vel{3}}{\ngp{1}} \frac{\vat{q}{\ngp{1} + \frac{1}{2}}}{2} \right).\]
\[\sumzf \sumyc \sumxc \vel{3} \ave{q}{\gcs{2}} = \sumzf \sumyf \sumxc \ave{\vel{3}}{\gcs{2}} q.\]
\[\sumzf \sumyc \sumxc \vel{3} \ave{q}{\gcs{3}} = \sumzc \sumyc \sumxc \ave{\vel{3}}{\gcs{3}} q.\]