N = 2 a − b·b − a′.
a − a′

(4)

Along a jet surface, q = Q, and

chΩ = cos θ = cos α − ½sin2 α(a − a′) / (u − b),

(5)

if θ = α at the source x of the jet xB, where u = ∞; and supposing θ = β, β′ at the end of the streams where u = j, j′,

u − b= ½sin2 α, u − j½sin2 α cosθ − cosβ,
a − a′ cos α − cos θa − a′ (cos α − cos β) (cos α − cos θ)
u − j′= ½sin2 α cos θ − cos β′;
a − a′ (cosα − cos β′) (cos α − cosθ)

(6)

and ψ being constant along a stream line