|Definition:|| quantity of dimension 1 characterizing the flow of a fluid in a given configuration characterized by a specified length l, defined by , where the fluid is described by its mass density ρ, speed v, dynamic viscosity η, and kinematic viscosity ν|
NOTE 1 The Reynolds number characterizes the relative importance of inertia and viscosity in a fluid flow.
NOTE 2 When the Reynolds number is less than a critical value Recrit, laminar flow is stable. For higher values of Re, laminar flow becomes unstable. The critical value depends on the configuration.
NOTE 3 In case of a fluid flowing through a circular tube with diameter d, the specified length is l = d, and the critical value of the Reynolds number is Recrit ≈ 2 300.