The Mechanical Engineering Handbook



Poiseuille's Law

Poiseuille's Law Equation



$$ Q = \frac{\pi r^4 (\Delta P)}{8 \mu L} $$ where:

Q   =   Volumetric Flow Rate   (m³/s)

r   =   Radius of pipe   (m)

Δ P   =   Pressure differecne between two points   (Pa)

μ   =   Dynamic Viscosity   (Pa s)

L   =   Length of pipe   (m)


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Equation Assumptions



  • The fluid is incompressible and Newtonian.
  • The fluid is in a steady flow.
  • The flow is laminar.
  • Flow is in steady-state.
  • End effects are negligible.