> > Okay, so lets talk about aerodynamic drag...o^)
> I know, I know, I know, I mean have some guesses :o))). When a car moves it
> leaves the air molecules that was behind it, so these molecules must be
> replaced, because vacuum is not acceptable within our atmosphere :o). This start
> of a vacuum behind the car will of course also pull on the car, thus drag. The
> principle is the same as in your vacuum cleaner, Bruce, it's as we had someone
> chasing us with a vacuum cleaner :o).
> With a wing it gets more complicated. Because the wing has forced the air
> upwards with speed it makes this air harder to suck in behind the car, hence the
> vacuum gets a little larger with a wing, and even larger with more wing :o).
> Now correct me :o).
Sure will! :))
This vacumn only occurs at high speeds and is more accurately termed "eddy" (or was
that Eddie?) or turbulance. Race cars and there wings are designed to be as
aerodynamically efficient as possible. They will enjoy perfect slipstreaming (shearing
effects close to the surface only) until the speed of air passing around them can no
longer act in a perfectly slipstreamed fashion and then eddies begin to form which is less
efficient.
From memory, this is what this all means mathematically.
Drag increases linearly whilst in perfect slipstreaming conditions. ie Drag =
Coefficient of drag (C) * Speed
the Coefficient of drag (C) in this example is related to the slipperiness of the
surface (special paints, etc) and for the entire car would be some type of average of the
sum of all the bits of the car ie tyres, wings, driver's helmet, body, etc, etc.
As different bits of the car enter into non slipstreamed behavior as speed increases,
then from this point the drag increases as the square of the speed.
ie delta Drag = C * (delta Speed) squared (Not completely sure)
So to use the front wing as an example, lets say it has perfect slipstreaming till
speed "Y" and that the speed of the car is Y + Z
Drag = [C * Y] + [C * (Z squared)] (Not completely sure)
I am rusty on this but you get the general idea.
What a sim developer quickly realizes here is that trying to do this to complete
accuracy is virtually impossible since it would involve modelling every single outer part
of the car and all their different C's and slipstream thresholds. So what could be done is
to just give the entire car an average "C" and slipstream threshold (my guess is this is
where most sims stand for now with only linear/overall adjustments for different wing
settings) or take it a step or 2 further and just model the most important bits. Perhaps
model front wheels and susp boxs as 1 piece, same for rear wheels/susp boxs, front and
rear wings, and, of course, the body/driver/helmet. I would think we should expect the
body/susp/tyres/driver/etc and wings to be modelled independantly in modern sims. ie
adjusting ride height at the front and rear would increase/decrease drag/downforce and
changing wing angles would adjust the drag/downforce for them and these 3 things should be
calculated independantly and their sum be the overall areodynamic model of the car. Maybe
Mike Lescault could enlighten us on any plans in this area for Cart Racing 2 and how it
was done in ICR2 :))
