Reynolds Number

A convenient number, called the Reynolds number, can be used for estimating the transition between laminar and turbulent flow. The Reynolds number, a ratio of flow rate to viscosity, can be computed by the relation:

R = Q (/) d (x) u (/) SG

Where:

R = Reynolds Number

Q = Flow in GPM

d = Pipe Diameter in inches

u = Viscosity in poises

SG = Specific Gravity

Laminar Flow exists if R is less than 63

Turbulent Flow exists if R is greater than 63

Whether flow is under Laminar or Turbulent conditions becomes extremely important when computing frictional losses in valves and fittings.