@Ogami
Yeah, the 1200kg overall figure was the second thing that got me thinking. I also considered it to be around 2,5t by last year. BTW I took a look at my Georigio Piola Book from 2000 where he stated, that the cars of that year had a total downforce of around 1600kg on average.
So if you say that 15% was the target, what was the ratio in 2008? 50%? 40%?
Much to one of my mistresses' disappointment, I amused myself last night with taking Om's figures for a spin and found something rather interesting.
If we begin with a 24000 N (2400 kg) total downforce at top-speed, 305 km/h (85 m/s). With a squared relation between speed and force, this results in half of that downforce, 12000 N, at 215 km/h (60m/s).
And for the sake of argument, with a contribution from diffuser and floor of 20% it means 2400 N at the same speed, 60 m/s, which with an estimated area of 2 sq. meters in turn would suggest an air-speed under the car of 75 m/s.
Now, imagine that Brawn with their "innovative" diffuser, manages to increase air-speed with 4%, from 75 to 78 m/s, downforce from diffuser and floor would jump from 2400 to 3000 N or 25%.
Overall downforce at 215 km/h, would as a consequence increase from 12000 to 12600 N or 5%.
On a curved section, everything else equal, a 5% increase in grip should in theory result in a 2.5% higher speed, when lateral force is m*v^2/R. With 40 seconds, or half the lap, spent in curves, it gives a 1.0 sec advantage over the whole lap.
Try that one for size, Ciro?
Last edited by xpensive on 01 Apr 2009, 09:10, edited 1 time in total.
"I spent most of my money on wine and women...I wasted the rest"
As a sidenote:
I always believed, that when anyone stated that those diffusers would be xx% better, he meant the increase in downforce for a given drag, not the air speed. Would you agree on that?
BorisTheBlade wrote:As a sidenote:
I always believed, that when anyone stated that those diffusers would be xx% better, he meant the increase in downforce for a given drag, not the air speed. Would you agree on that?
For a diffuser, the drag is relatively independant of downforce created.
Therefore the car drag levels will be more dependant on car speed.
Hm,
I know that it's only a small portion compared to overall drag. But in terms of efficiency there's always a denominator.
My whole point is:
If they talk about havin improved the diffusor by like 20%, do the talk about 20% more [downforce]/[drag] or do they talk about 20% more [air speed under the car]/[over the car]? Cause seeing these calculations it'd make a huge difference.
When knowing a few journaists Boris, it is sometimes difficult to know precisely what they mean, or even if they have a technical clue what they are talking about.
With the shining exception of scarbs of course.
My guess is that if anyone talks about "improving the diffuser with 20%", what they really mean is that the downforce generated by the entire floor has increased by 20%. kilcoo?
"I spent most of my money on wine and women...I wasted the rest"
xpensive wrote:
My guess is that if anyone talks about "improving the diffuser with 20%", what they really mean is that the downforce generated by the entire floor has increased by 20%.
Callum wrote:ah right, the ram effect is what i was getting at.
Oh, another thing, which may be a reallly simple/stupid question..
How is the car travelling through static air the same as moving air through a static car...?
Thanks Conceptual.
Confused?
Quick question after reading Simons book as well...
Why would vortex sealing of the skirt area be better than a saw-tooth edge that would generate vorticies as air was sucked under?
There is a picture in his book that shows a single vortex on either side being sucked under the car, and leading to some VERY low pressure areas, and an increase of mass flow.
THAT is what doesn't make a lot of sense to me, so if anyone can explain, I would be greatly appreciative!
Not only a downforce increase but remember a well-designed diffuser will reduce pressure-drag (or form-drag, whatever you want to call it)...
Conceptual: I have a sneaking suspicion that your concept wouldn't improve mass-flow under the floor because you are creating vortices all along the length (each 1/n in size) instead of a single, full-length vortex of n length. Remember vortices propagate along a length so trying to stimulate them by using a serrated edge may result in dissipating of the vortex reducing it's effect. However, this is all just my sneaking suspicion - you'd need to test it really.
Conceptual wrote:There is a picture in his book that shows a single vortex on either side being sucked under the car, and leading to some VERY low pressure areas, and an increase of mass flow.
THAT is what doesn't make a lot of sense to me, so if anyone can explain, I would be greatly appreciative!
That is trying to get the same effects as a LERX.
I would have thought the restricted area between the ground plane and car floor (and associated friction) would limit the application of this. But I cannot be 100% on that.
xpensive wrote:My guess is that if anyone talks about "improving the diffuser with 20%", what they really mean is that the downforce generated by the entire floor has increased by 20%. kilcoo?
My take on it too - effectively an improvement of 20% on -CL.
Any body remember how the diffuser works.. I would like to see some on that. The whole transitioning effects and all. I want somebody to remember it for me hehehe.
Last thing i remember from school was some length vs pressure thing.
kilcoo; If my sketchy calculations from Wed Apr 01, 2009 6:33 am is anything to go by, my reflection is that this is an extremely sensitive component, why either a standard-floor or a flat-bottom rule all the way might be the way to go for the FIA, if they are serious abut draconian cost-cuttings?
"I spent most of my money on wine and women...I wasted the rest"
xpensive wrote:kilcoo; If my sketchy calculations from Wed Apr 01, 2009 6:33 am is anything to go by, my reflection is that this is an extremely sensitive component, why either a standard-floor or a flat-bottom rule all the way might be the way to go for the FIA, if they are serious abut draconian cost-cuttings?
Well... getting that past the teams would be an ordeal.
In principle, I agree with standardising it - it is an unseen element. But in getting rid of it, would that remove F1 from being the quickest cars around a race circuit in the world?
Perhaps a standard floor from a certain distance behind the cockpit is the best solution... and use the current OWG envisaged diffuser.
