Dimensionless quantity characterising the ratio of inertial forces to viscous forces and corresponding fluid flow regime:
| (1) | {\rm Re} = \frac{{\rm Inertial} \ {\rm forces}}{{\rm Viscous} \ {\rm forces}} = \frac{u \, L}{\nu} = \frac{\rho \, u \, L}{\mu} |
where
u | average cross-sectional flow velocity |
L | characteristic linear dimension of the fluid conduit |
\rho | fluid density |
\mu | dynamic viscosity |
\nu | kinematic viscosity |