Reynolds number

Summary

The Reynolds number $\mathrm{Re} = U L / \nu$ is the dimensionless number that compares inertial forces with viscous forces in a flow. At small Reynolds number viscosity dominates and flows are smooth and orderly. At large Reynolds number inertia dominates and flows tend to become unstable and turbulent. It is the main parameter of the incompressible Navier–Stokes equations after they are made dimensionless.