Eliminating H between (5) and (6)
| Dξ | − ξ | du | − η | dw | − ζ | dv | + ξ ( | du | + | dv | + | dw | ) = 0, |
| dt | dx | dx | dx | dx | dy | dz |
(9)
and combining this with the equation of continuity
| 1 | Dρ | + | du | + | dv | + | dw | = 0, | |
| ρ | dt | dx | dy | dz |
(10)
we have
| D | ( | ξ | ) − | ξ | du | − | η | dv | − | ζ | dw | = 0, | |||
| dt | ρ | ρ | dx | ρ | dx | ρ | dx |
(11)
with two similar equations.