Laminar Flow - Friction Coefficients
The friction coefficient - or factor - of a fluid flow at laminar conditions can be calculated as
λ = 64 / Re
= 64 μ / (d h u ρ)
= 64 ν / (d h u) (1)
where
λ = friction coefficient (non-dimensional)
Re = Reynolds Number (non-dimensional)
μ = absolute (dynamic) viscosity (Ns/m 2 , lb m /s ft)
d h = hydraulic diameter (mm, ft)
u = mean velocity in flow (m/s, ft/s)
ρ = density of fluid (kg/m 3 , lb m /ft 3 )
ν = μ / ρ = kinematic viscosity (m 2 /s, ft 2 /s)
Equation (1) is only valid at laminar conditions where Reynolds Number is less than 2300 . For turbulent conditions where Reynolds Number exceeds 4000 the Colebrook equation should be used to calculate the friction coefficient.
In practice laminar flow is only actual for viscous fluids - like crude oil, fuel oil and other oils.
The friction coefficient for laminar flow indicated in the Moody diagram (SI based):
Related Topics
• Fluid Mechanics
The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.
Related Documents
Colebrook Equation
Friction loss coefficients in pipes, tubes and ducts.
Darcy-Weisbach Equation - Major Pressure and Head Loss due to Friction
The Darcy-Weisbach equation can be used to calculate the major pressure and head loss due to friction in ducts, pipes or tubes.
Reynolds Number
Introduction and definition of the dimensionless Reynolds Number - online calculators.