Lift Coefficient

on . Posted in Dimensionless Numbers

Lift coefficient, abbreviated as \(C_l\), a dimensionless number, normally used in aerodynamics to quantify the lift generated by an airfoil, wing, or other aerodynamic body as it moves through a fluid, typically air.  It's an essential parameter in aircraft and aerodynamics analysis, providing insights into the lift producing characteristics of different shapes and configurations.  The lifting body can be a foil or a complete foil bearing body such as a fixed wing aircraft.

The lift coefficient is used to normalize the lift force by the dynamic pressure and the reference area.  This normalization allows for direct comparison of lift characteristics across different airfoil shapes, sizes, and flow conditions.  Aircraft designers and engineers use lift coefficients to optimize the performance of wings and airfoils for specific applications, such as minimizing drag, maximizing lift, and ensuring stable flight characteristics across a range of conditions.

Key Points about Lift Coefficient

  • It's a measure of how effectively an airfoil or wing generates lift.
  • Different airfoil shapes and angles of attack will result in different lift coefficients.
  • Lift coefficient depends on the angle of attack, airfoil design, and other factors.
  • Lift coefficient is often plotted against angle of attack to create lift curves or polar plots.
  • The lift coefficient can be used in conjunction with the drag coefficient to analyze the trade off between lift and drag in various flight conditions.


Lift Coefficient formula

\( C_l \;=\; 2 \; L \;/\; \rho \; v^2 \; A \)
Symbol English Metric
\( C_l \) = lift coefficient \( dimensionless \)
\( L \) = lift force \( lbf \) \(N\) 
\( \rho \)  (Greek symbol rho) = density of fluid \(lbm \;/\; ft^3\) \(kg \;/\; m^3\)
\( v \) = velocity \(ft \;/\; sec\) \(m \;/\; sec\)
\( A \) = area of surface \( ft^2 \) \( m^2 \)


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Tags: Pressure Coefficient Air