Lift Force

Lift force arises primarily due to the pressure difference across the surface of an object as it moves through a fluid. Viscous effects, such as shear stress, are secondary in the creation of lift.

Lift force $F_L$ is defined as

$$F_L=C_L\frac{1}{2}\rho V^{2}A$$

where $C_L$ is the lift coefficient, $\rho$ is the density of the fluid, and $A$ is the reference area.

The lift coefficient $C_L$ is influenced by several factors:

$$C_L=C_L\left(\text{Re},\frac{ϵ}{L},\text{Ma},\text{Fr},\text{Shape}\right)$$

• Re – Reynolds number, representing the ratio of inertial forces to viscous forces
• $\frac{ϵ}{L}$ – Relative surface roughness to characteristic length
• Ma – Mach number ($V/c$), the ratio of velocity to the speed of sound.
• Fr – Froude number ($V/\sqrt{gL}$), representing inertial forces to gravitational forces
• Shape – The aerodynamic design of the airfoil or object