[ODE] [off-topic] Modelling aerodynamics

[Thomas Harte]

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>thats a great idea
>
>> - assume that vehicle only generates downforce when travelling forwards. Assume
>> that the car will really only usually travel forwards, and simply apply a downward
>> force that is in some way a function of body velocity

I looked it up, apparently the correct formula to work out the aerodynamic drag on a 
vehicle is :

Fd = 0.5*rho*Cd*A*V^2

Where

Fd = drag force
rho = air density
Cd = drag coefficient
A = front area of the vehicle
V = velocity

Lift is then defined, using the same variables as :

Cl = 0.5*rho*Cl*A*V^2

Where : Cl = aerodynamic lift constant. Interestingly, in normal passenger cars, Cl is 
actually positive (between 0.3 and 0.5), causing such a car to loose rather than gain 
downward force at high speeds. I would dare imagine that very much the opposite is not 
true of racing cars, although the document I am using 
(http://www.gdconf.com/archives/2000/zuvich.doc) is not specific.

So, to sum up, downforce (or upforce as it may turn out to be) may be modelled in a 
simplified manner as proportional not to [the length of] 'forward velocity', but to the 
square of that velocity.

-Thomas

Free Email at http://www.lycos.co.uk


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