Amount and distribution of downforce in a 2003 F1 car

[timbo]

The coefficient of lift wont be calculated for an F1 car, it will be found in the wind-tunnel or CFD because it runs directly from chord length and plan area etc - something that isn't directly applicable.

Oh and I've been an eejit, it's F = 1/2*rho*A*U^2*Cl - woops

The area is the plan area - the surface area that the air is subject to. 2.75 (or whatever it is after you redo it without my idiocy included) on a car that is 4.5x1.8 metres does seem a bit low but when you consider the size of the floor and the wings, it might not be too far off.

I had 1/2 already included from that NASA link)))
Well, Maybe 2.75 isn't too far off... The floor width is 1.4 meter I believe? With all the cut outs and length about 2 meters it should be close.

[xpensive]

Assumed a 2.75 m^2 top-view area of the entire car and given that 2.617 is the CL of the same, total aerodynamical downforce would be 19200 N at 240 km/h and 1.2 density.
Is that reasonable?

[timbo]

Assumed a 2.75 m^2 top-view area of the entire car and given that 2.617 is the CL of the same, total aerodynamical downforce would be 19200 N at 240 km/h and 1.2 density.
Is that reasonable?

It is not different from your previous estimation))))

I think someone brave should take the task of calculating area of F1-2000

[xpensive]

Correct, but that was just based on Scot's 30 kN-number at 300 km/h.

I figure 2.75 should not be that far off, but counting wheels and all, I don't know really.

[timbo]

Correct, but that was just based on Scot's 30 kN-number at 300 km/h.

I figure 2.75 should not be that far off, but counting wheels and all, I don't know really.

If you look at the numbers, wheels are providing lift, so that is effectively deducted from the total area.

[GGSF1]

First of all thanks to all for your answers.

After reading this I think that the values that timbo posted are lift and drag coefficients.

Scotracer said that a 2004 F1 car has got around 3000 kg of downforce at 300 km/h. I think that value is way too high, considering that in the link I have posted it's said that a car has got 1694 kg of downforce at 292 km/h, and I don't think cars evolved too much from 2000 to 2003. I don't know much aerodynamics so I could be wrong though.

Also, I thought that to calculate both downforce and drag values you need the frontal aera, but some people in this forum is talking about top area, so what is the correct value to use?

Using the front area this is what I get: 0.5*1.2 (air density)*2.617 (lift coefficient)*1.6 (front area, it is for sure less than 1.8 so I'll use 1.6)*83.3^2 (speed in m/s) = 17432.71 N = 1778.85 kg at 300 km/h

I think it's a reasonable value, but I am using front area since I found that front area was used in aerodynamic calculations. What I don't know is if it only needs to be used in drag or it must be used in both drag and downforce.

[Scotracer]

1778kg is far too low. Mike Gascoyne did a feature in 2007 or 2008 where he talked about Force India's aerodynamics and mentioned they were producing 2800kg of downforce at the end of the main straight at Barcelona (which is just over 300km/h). I'm trying to find a link. But what it does show is that 2004 will be even higher when the lower front wing, bigger diffuser and more effective rear wing.

[GGSF1]

So that information I found is right:

An F1 car has got the same downforce:weight ratio of 1:1 at 125 km/h (78 mph) to 130 km/h (81 mph), and at 190 km/h (118 mph) the ratio is roughly 2:1.

Taken from here

[timbo]

So that information I found is right:

An F1 car has got the same downforce:weight ratio of 1:1 at 125 km/h (78 mph) to 130 km/h (81 mph), and at 190 km/h (118 mph) the ratio is roughly 2:1.

Taken from here

It's 120kN at 190kph, not 240. And that figure gives you 29.9kN at 300 just as Scotracer said.

[Scotracer]

*smug*

[GGSF1]

So that information I found is right:

An F1 car has got the same downforce:weight ratio of 1:1 at 125 km/h (78 mph) to 130 km/h (81 mph), and at 190 km/h (118 mph) the ratio is roughly 2:1.

Taken from here

It's 120kN at 190kph, not 240. And that figure gives you 29.9kN at 300 just as Scotracer said.

I know, I just was saying that that information matched the one that Scotracer said. I will try to implement the values in the game to know how if the car behaves by a realistic way.

Another question I have, what is roughly the difference of downforce between a slow car and a fast car? I guess it's a small value, since differences between cars are only a few tenths of a second.

And finally, when you use the formula 0.5*rho*area*coefficient*speed^2, the area is measured from the front or is it measured from the top? I'm not sure of that.

PS: Sorry for asking too much, but I have no idea when it comes to aerodynamics

[Scotracer]

Taken from here

It's 120kN at 190kph, not 240. And that figure gives you 29.9kN at 300 just as Scotracer said.

I know, I just was saying that that information matched the one that Scotracer said. I will try to implement the values in the game to know how if the car behaves by a realistic way.

Another question I have, what is roughly the difference of downforce between a slow car and a fast car? I guess it's a small value, since differences between cars are only a few tenths of a second.

And finally, when you use the formula 0.5*rho*area*coefficient*speed^2, the area is measured from the front or is it measured from the top? I'm not sure of that.

PS: Sorry for asking too much, but I have no idea when it comes to aerodynamics

I think you're just going to have to test it - change values until you get the rough laptime difference between the fastest and slowest cars. A lot of mods have assumed the same physics and changed the base weight accordingly. I don't like this method, but it works.

Oh and it's the plan area.

[xpensive]

Settling for 12 kN total downforce at 190 km/h and 40% of that comes from the floor, we have 3.6 kN over what, 2 m^2?

Bernoulli tells us that this comes from the difference in static pressure as a result of difference in air-velocity, where 3600 N over 2 m^2 means 1800 Pa.

ps1 - ps2 = pd2 - pd1 = 1800, pd = Rho * v^2/2, v1 = 52.8 m/s, v2 = ?

Conclusively, the air-speed under the floor must be 76 m/s in order to produce 3.6 kN.

[timbo]

The real treat would be estimating somehow CL changes with respect to car attitude at least at braking and accelerating.

[tahadar]

The real treat would be estimating somehow CL changes with respect to car attitude at least at braking and accelerating.

you would have to go into a windtunnel for that, because car Cl is very sensitive to ride height changes (which occur under braking and acceleration).