An Etymological Dictionary of Astronomy and Astrophysics
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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).

→ Rayleigh; → criterion.