[ODE] Stabilizing Cars and Aerodynamics

[Jon Watte]

A gentleman named Umberto told be that air lift/load is 
indeed proportional to velocity squared (so I'll go update 
my model!) In fact, the lift formula is pretty much the 
same as the drag formula.

He also suggested the link:
http://www.nas.nasa.gov/About/Education/Racecar/

and re-iterated the air drag formula, addint the almost 
identical air lift formula:

D = 0.5 * cD * ro * A * v^2
L = 0.5 * cL * ro * A * v^2

D = drag force
L = lift force
cD = coefficient of drag. it depends basically on the shape of the car. 
Production cars have a cD of 0.3 - 0.4. For Formula cars it varies 
depending on the tracks: it goes about from 0.7 to 1.3
cL = coefficient of lift. It can be positive (lift) or negative (load). 
It's a value around 0.1. In Formula cars it varies from about -2 to -4. If 
cL is negative L is called downforce.
ro = air density
A = frontal area of the car (from 1.3 to 1.8 square meters)
v = speed

For an airplane, you want cL to be positive and L to point upwards. 
For a race car, you want cL to be negative and L to point downwards :-)

Cheers,

			/ h+


--
  "Consider a spherical cow of uniform density..." -- Feynman