View Single Post
  #53   Report Post  
Posted to uk.d-i-y
The Real Doctor The Real Doctor is offline
external usenet poster
 
Posts: 140
Default Graph of car fuel consumption versus speed

On 8 Oct, 13:26, Martin Bonner wrote:

I *think* that the force exerted by drag goes as the /square/ of the
speed. *


Only for a constant drag coefficient. Cd itself, however, depends on
the flow pattern around the car and that in turn depends on the speed
- it's often expressed in term of the Reynolds number. As speed
increases the flow becomes more turbulent and drag increases
enormously. Conversely, when the speed is low the flow is (largely)
laminar and drag is low.

Ian