Lift coefficient#
$$C_L \stackrel{\text{def}}{=} \frac{F}{\rho U^{2} A} \sim \frac{\text{lift force}}{\text{dynamic pressure force}}$$
Description#
Measures lift force normalized by dynamic pressure and reference area. It compares lifting performance across geometries, speeds, and fluid densities.
Quantities#
| Name | Symbol | SI units | Dimension |
|---|---|---|---|
| force | \(F\) | \(\mathrm{N}\) | \(\text L\,\text M\,\text T^{-2}\) |
| mass density | \(\rho\) | \(\mathrm{kg}\,\mathrm{m}^{-3}\) | \(\text L^{-3}\,\text M\) |
| velocity | \(U\) | \(\mathrm{m}\,\mathrm{s}^{-1}\) | \(\text L\,\text T^{-1}\) |
| reference area | \(A\) | \(\mathrm{m}^{2}\) | \(\text L^{2}\) |
Regimes#
Lifting surfaces
| Range | Regime | Description |
|---|---|---|
| 0 – 0.1 | weak lift | Lift is small relative to the dynamic pressure force on the reference area. |
| 0.1 – 1 | moderate lift | Lift is appreciable and sensitive to angle of attack, shape, and Reynolds number. |
| 1 – ∞ | strong lift | Lift is large relative to the reference dynamic pressure force; stall, circulation, or strong pressure differences may dominate behavior. |