Courtin number

The Courtin rotational parameter is a dimensionless number used in rotational flow calculations. It expresses the relationship between the torque and angular velocity of a rotating flow. Its main application is in problems involving one cylinder rotating inside another separated by viscous incompressible fluids.

It is defined as:

: $C\; =\; frac\{\; au\}$omega^2}{D_i^5}{ ho

where

*$au$ is the torque;

*$omega$ is the rotational velocity;

*$ho$ is the liquid density;

*$D\_i$ is the diameter.