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# Laminar Flow - Friction Coefficients

## 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 / (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.

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.

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## Citation

• The Engineering ToolBox (2008). Laminar Flow - Friction Coefficients. [online] Available at: https://www.engineeringtoolbox.com/laminar-friction-coefficient-d_1032.html [Accessed Day Month Year].

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9.29.12