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Dimensionless quantity characterising the ratio of inertial forces to viscous forces and corresponding fluid flow regime:

{\rm Re} = \frac{{\rm Inertial} \ {\rm forces}}{{\rm Viscous}  \ {\rm forces}} = \frac{u \, L}{\nu} = \frac{\rho \, u \, L}{\mu}

where

average cross-sectional flow velocity

characteristic linear dimension of the fluid conduit

fluid density

dynamic viscosity

kinematic viscosity 



See also


Physics / Fluid Dynamics / Fluid flow regimes