Wind Tunnel Testing

What do wind tunnels do?

  • How air flows around (or through) an object
  • Calculate drag and lift
  • Record velocity, temperature and pressure on object

How do wind tunnels work?

  • Move air past the object rather than the other way around
  • Consistent air flow
  • Make measurements

Open loop wind tunnels

Closed loop wind tunnels


  • Benjamin Robbins (1746): Horizontal arm on vertical pole (Drag)
  • Frank Wenham (1871): 3.7m by 46cm (64 kph)
  • Wright Brothers (1901): 40.6 cm width
  • Ames test facility (1921): 430m long, 24m by 37m wide.

Benjamin Robbins: Whirling arm

Wright Brothers:

Ames Wind Tunnel:

Size matters!

  • Viscosity (stickiness)
  • Compressibility (bounciness)


Wind tunnel measurements:

  • Flow visualisation: Smoke, string, laser anemometers
  • Pressure: Pitot tubes
  • Temperature: Thermometers



Laser Anemometer

Pitot Tubes

Lift vs Drag:

Best Lift Maximisation

Best Drag Minimisation

Laminar vs turbulent flow:

Laminar flow:

  • Streamline flow
  • No disruption between layers
  • Well understood


  • Turbulent flow contains eddies (vortices) and small packets
  • Lateral mixing
  • Chaotic (Butterfly effect, not random)

Computer Modelling:

Computational Fluid Dynamics: