Calculate friction coefficients for laminar fluid flow.
The friction coefficient - or factor - of a fluid flow at laminar conditions can be calculated as
λ = 64 / Re
= 64 μ / (d hu ρ)
= 64 ν / (d hu) (1)
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):