An Etymological Dictionary of Astronomy and Astrophysics

A criterion for the instability of a basic swirling flow with an arbitrary dependence of angular velocity Ω(r) on the distance r from the axis of rotation. This states that in → inviscid fluids:

Ω(r) < 0 for instability, where Ω = (1/r³) (d/dr)(r⁴Ω⁴).

See also: → Rayleigh; → criterion.