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Aerodynamics

The science of air in motion and its interaction with solid bodies. Aerodynamics governs lift generation, drag reduction, and stability - the fundamental challenges of flight from subsonic propeller aircraft to hypersonic re-entry vehicles.

Airfoil Pressure Visualization

Angle of Attack: 5\u00B0

Lift Coefficient (C_L)

Flow State

Attached

Key Facts

Lift is generated primarily by pressure differences between upper and lower airfoil surfaces, explained by circulation theory
The four forces of flight: lift, weight, thrust, and drag
Boundary layer transition from laminar to turbulent flow significantly affects drag
Mach regimes: subsonic (M<0.8), transonic (0.8<M<1.2), supersonic (1.2<M<5), hypersonic (M>5)
Shock waves form at supersonic speeds, causing wave drag and temperature spikes
The lift coefficient depends on angle of attack, airfoil shape, and Reynolds number
Induced drag results from wingtip vortices and is inversely proportional to aspect ratio
Stall occurs when the angle of attack exceeds the critical value and flow separates from the upper surface

Fundamental Equations

Lift Equation

L = \frac{1}{2} \rho v^2 S C_L

Total lift force as a function of air density, velocity, wing area, and lift coefficient.

Drag Equation

D = \frac{1}{2} \rho v^2 S C_D

Total drag force, analogous to lift but using the drag coefficient.

Lift-to-Drag Ratio

\frac{L}{D} = \frac{C_L}{C_D}

A measure of aerodynamic efficiency; higher is better for range and endurance.

Thin Airfoil Theory

C_L = 2\pi \alpha

Lift coefficient for a thin symmetric airfoil at small angles of attack (in radians).

Mach Number

M = \frac{v}{a} = \frac{v}{\sqrt{\gamma R T}}

Ratio of flow velocity to local speed of sound, the key parameter for compressible flow.

Induced Drag

C_{D_i} = \frac{C_L^2}{\pi e AR}

Drag due to lift, dependent on span efficiency factor e and aspect ratio AR.