There are two dimensionless groups named Taylor number. The first is used as a criterion for the stability of flow in an annulus surrounding a rotating cylinder.
where ω is angular velocity (s−1), Ra is the mean radius of the annulus, a is the width of the annulus, and ν is fluid kinematic viscosity. (Sometimes the square of this quantity is used to define Taylor number, see Taylor Instability.)
The second Taylor number represents the square of the ratio of Coriolis Force to viscous force, i.e.,
