Aviation & Aeronautics
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Reynolds Number

Ratio of inertial to viscous forces; characterises airflow over an airfoil.

Formula

Re=ρvLμRe = \dfrac{\rho v L}{\mu}

Variables

ReReynolds number
\rhoDensity
vVelocity
LChord length
\muDynamic viscosity

Example

Model aircraft fly at low Reynolds numbers, so their airflow behaves quite unlike a full-size jet’s.

Did You Know?

Insects, model planes, and airliners fly in vastly different Reynolds-number regimes, so their wings differ wildly.

reynoldsaerodynamicsboundary layer