Aerodynamic Drag

AERODYNAMIC DRAG is the resistance (measured as a force) produced by the movement of a fluid (usually air) across the surface of a body. It is dependent upon the shape of the body, the relative (speed)2 between the fluid and the body, and the projected frontal area of the body. Hence, for a vehicle having a frontal area A (m2), a relative speed of V (m/s) and a coefficient Co, as the drag coefficient, for the shape of the vehicle body.

The Aerodynamic Drag = CoAV2 (NEWTONS)

Note:

1. For most vehicles, the aerodynamic drag becomes significant at relative speed, above 80km/h.
2. A head wind of 50km/h with a vehicle road speed of 50km/h is equivalent to a 100km/h wind on a stationary.
3. A tailwind of 50km/h with a vehicle road speed of 50km/h is equivalent to dead calm air on a stationary vehicle and hence zero aerodynamic drag.
4. The power to overcome such drag conditions is obtained by multiplying the drag force by the vehicle speed.

I.e. Aerodynamic Tower = Drag Force x Road Speed = CoAV3 (RW)

It is the cubic power, of road speed, that dictates the need for very high-powered engines, in racing cars.