Reynolds Number

(Re, N _Re ) \^▐re-n^әldz-\ n [Osborne Reynolds † 1912 English physicist] (1910) The Reynolds number Re is the ratio of kinetic energy to viscous energy; the equation is,

$${\mathop{\rm Re}\nolimits} = 2rds/vd = 2rs/vk$$

where

s = speed of the fluid, cm/s,

r = radius of tube, cm

d = fluid density

vd = dynamic viscosity, Poise (dyne-s/cm²)

vk = kinetic viscosity in Stokes (vd d)

Re = Reynolds number; small Re means that the fluid’s viscosity is dominant, large Re (10,000) means viscosity is negligible and the kinetic or inertia effects rule; when Re is high, turbulent, cavitations and chaos describe the flow, when Re is low, laminar flow dominates.

(2) A dimensionless ratio that relates to frictional pressure drop in fluid flow in pips, defined by DċVċρ/μ for gasses and Newtonian liquids, where D is the inside pipe diameter, V is the average velocity of the fluid (= flow rate/cross-section), ρ is the fluid density, and μ is the mass-based viscosity [Pa = kg/(mċs) in SI units]. When N_Re=...