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# 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 hu ρ)

= 64 ν / (d hu)                          (1)

where

λ = friction coefficient (non-dimensional)

Re = Reynolds Number (non-dimensional)

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

d h= hydraulic diameter (mm, ft)

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

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

ν = μ / ρ = kinematic 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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