| dv | − 2wξ + 2uζ + | dH | = 0, |
| dt | dy |
(5)
| dw | − 2uη + 2wξ + | dH | = 0, |
| dt | dz |
(6)
where
H = ∫ dp/ρ + V + ½q2,
(7)
q2 = u2 + v2 + w2,
(8)
and the three terms in H may be called the pressure head, potential head, and head of velocity, when the gravitation unit is employed and ½q2 is replaced by ½q2/g.