Corner Radius for Corners of the Gilles Villeneuve Circuit

[al_garnett]

Hey,

I'm completing a CFD project at uni regarding front wing and the angle of attack.

For my hand calculations i am using the centripetal force equation to calculate the force which will subsequently be used in the tyre friction force equation to calculate downforce.

For this i need to know the radius of each corner, Could anyone tell me how to calculate this or direct me somewhere that they are published?

Furthermore does anyone have an idea of the value i should use for the coefficient of friction for the 2010 Bridgestone tyres?

Any help would be greatly appreciated.

Thanks
Alex

[MadMatt]

For the radius of the corners, why don't estimate them from Google Earth? That's gonna be your only option I'm afraid.

Coefficient of friction wise, again you'll have issues finding this value, but it is way over 1

[Tim.Wright]

I'm not completely understanding why you require the trajectory radius. If you look on the F1 site, you can see the speed and lateral acceleration at many of the corners and from that information you should be able to calculate the downforce.

If you really want to know the corner radius, then its equal to V^2 / LatAcc.

[al_garnett]

I'm not completely understanding why you require the trajectory radius. If you look on the F1 site, you can see the speed and lateral acceleration at many of the corners and from that information you should be able to calculate the downforce.

If you really want to know the corner radius, then its equal to V^2 / LatAcc.

I used your advice and calculated the radius using lateral acceleration. I subsequently used the centripetal force, Fc=m*V^2/R and then Fc=tyre friction * (weight of car + Downforce) to calculate the downforce.

However in corners with low lateral acceleration i am getting results of a negative value for downforce and i can't get my head around it.

Any ideas?

[Tim.Wright]

Post your calcs, it will be easier for us to analyse.

[Lycoming]

I'm confused, are you trying to calculate corner radius or downforce?

[Reca]

Here a plausible racing line computer generated, using speed data of Rosberg’s 2014 pole (from analysis of engine noise) and track’s boundaries (from satellite image), with the aim of minimizing an opportune fitness function of the resulting lateral acceleration and other parameters:


And here the corresponding radiuses (numbers are only to give you an easy visual correspondence between the graphs, not corner’s “names”):


Obviously it’s not the exact representation of the racing line Rosberg followed, just a reasonable trajectory to get an hopefully close estimate of lateral acceleration (it’s very simplified, mass point), but should be good enough for your needs.

BTW, I’d be interested in knowing the reasons that made you pick Canada, of all tracks, for the project you describe, not sure it’d be my first choice.

However in corners with low lateral acceleration i am getting results of a negative value for downforce and i can't get my head around it.

You get negative downforce in some places because you are imposing a too high friction coefficient for these corners, which results in an underestimated vertical force, even lower than car’s own weight.
These low lat acc corners are easily flat out, power limited, lateral force required is far from the max the car is capable of, so the friction coefficient effectively used is lot lower than max.
For your needs, these corners should just be ignored, effectively straights.

[MadMatt]

Fair play Reca, nice post! Did you do the sound analysis directly in your matlab script as well in an (semi)automatic fashion?

As for the track boundaries, what was your methodology? Manually picking point on the satellite picture? I recon it would be great to just give matlab 1 point on a satellite view which is on the track, and let matlab find the boundaries, knowing that the track is of a gray-ish colour (escape roads and tarmac run-off areas might be a problem tho).

[Tim.Wright]

If the goal is to calculate the tyre friction coefficient and the downforce, there is a much simpler way:

1. For a given circuit (or better still a number of circuits with similar aero setups) make note of the velocity and lateral acceleration through each corner. You can take this from an onboard lap or from one of the track diagrams that the various teams put out.

2. Put all of these datapoints on a scatter plot with speed as the horizontal axes and lateral acceleration as the vertical axes.

3. Fit a squared polynomial to the data in the form: LatAcc = a.Speed^2 + b

4. Then you have:
Tyre friction coefficient: mu = b/9.81
Downforce: SCz = (2 x mass x a)/(mu x AirDensity)

[Ciro Pabón]

Reca!

I'm so happy reading your post.

Best post of the year, no doubt.

[al_garnett]

If the goal is to calculate the tyre friction coefficient and the downforce, there is a much simpler way:


3. Fit a squared polynomial to the data in the form: LatAcc = a.Speed^2 + b

4. Then you have:
Tyre friction coefficient: mu = b/9.81
Downforce: SCz = (2 x mass x a)/(mu x AirDensity)

Thanks for your help everyone.

Tim I was wondering if you expand on point 3 and 4 for me please?

[al_garnett]

My actual aim is once i have calculated the required downforce levels for each corner is to complete CFD/FEA simulations on my front wing model to select the optimum angle of attack for this circuit.

I chose the Gilles Villeneuve circuit due to the medium downforce requirements, preventing the requirement to make changes to my front wing model

[hollus]

Does it matter at all if you get the values exactly right? If they are a bit off, then you will be optimizing you wing for your own version of the Gilles Villeneuve circuit, which doesn't change the engineering task at all.
I think google maps derived radiuses are more than enough, and you would have the values by now.

[al_garnett]

I have calculated the radii for each corner as i know the g force and velocity at each corner and were found using the following equations.

Radius=Velocity^2/Lateral Acceleration

where Lateral Acceleration= g force * 9.81


Using these Radii i can calculate the centripetal force for each corner using Fc=mass * Velocity^2/Radius.

This is where the problem arises whilst using the following tyre friction force equation...

Fc= Tyre Friction Coefficient * Fnormal


Fnormal consists of two parts. The weight of the car, Mass*gravity, and the downforce. Therefore rearranging this equation to find downforce results in the following.

Downforce=(Fc/tyre friction coefficient)-(mass of car*gravity)

As the tyre friction coefficient varies from corner to corner this is providing me with negative values on several corners. This is where my problem lies

[SuperDrummer]

Here a plausible racing line computer generated, using speed data of Rosberg’s 2014 pole (from analysis of engine noise) and track’s boundaries (from satellite image), with the aim of minimizing an opportune fitness function of the resulting lateral acceleration and other parameters:
http://i.imgur.com/lMfZv1U.jpg

What looks really strange for me on this speed plot is the changing slope in braking area, especially for the last 2 corners, the hairpin and the final chicane. If I would have seen such a graph not knowing that is was Rosberg, I would assume that we are dealing with a very inexperienced driver.
What might be the reason for this? Just expected inaccuracy of Mercedes engine noise analysis?