# Friction Coefficient with Laminar Flow

## Laminar flow and friction coefficient

The friction coefficient - or factor - of a fluid flow at laminar conditions can be calculated as

λ = 64 / Re

= 64 μ / (dh u ρ)

= 64 ν / (dh u)                          (1)

where

λ = friction coefficient (non-dimensional)

Re = Reynolds Number (non-dimensional)

μ = absolute (dynamic) viscosity  (Ns/m2, lbm/s ft)

dhhydraulic diameter (mm, ft)

u = mean velocity in flow (m/s, ft/s)

ρ = density of fluid (kg/m3, lbm/ft3  )

ν μ / ρkinematic viscosity (m2/s, ft2/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.

## Related Topics

• Fluid Mechanics - The study of fluids - liquids and gases. Involves velocity, pressure, density and temperature as functions of space and time

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