F1technical.net

Pieoter wrote:They probably already have enough downforce from the undercar tunnels and the rest of the package.

Possible only have a rear wing due to regulations, looks like an aero neutral profile.

Pretty much, just there mostly to tune the aero-balance of the car.

WilliamsF1 wrote:

Champcar were ground effect cars, however Indy........................ not sure....

Helio's car looks like a diffuser rather than a venturi tunnel (I may be wrong)

The closest answer that I have is that F1 diffusers can't start before the centreline of the rear axle and cannot have any curvature to the bottom. The tunnel on the Indycar starts well before the rear wheel and has a curved bottom profile.

hpras wrote:

Pieoter wrote:They probably already have enough downforce from the undercar tunnels and the rest of the package.

Possible only have a rear wing due to regulations, looks like an aero neutral profile.

Pretty much, just there mostly to tune the aero-balance of the car.

If it's effective enough to have a positive impact, it's effective enough to have a negative impact, yanno?

ESPN wrote:"On a higher downforce configuration, the endplates add more aerodynamic power and value, and we didn't need them," he continued. "The main plane looks very small because we can make a very efficient wing for oval events. It actually has just as much [aerodynamic] strength as the old wing and most of the time it's just providing a small amount of trim. It also has the nice side effect of lighter weight, which is a big factor for these cars."

The question is whether Chevrolet went too far in its quest for efficient downforce. Is the lack of rear-wing endplates contributing to the way the cars are suddenly snapping loose without warning, and to the seeming propensity for them to fly?

[...]

In an effort to maintain secrecy about their designs, Chevrolet and Honda did little on-track testing, by traditional standards, trusting their designs to wind-tunnel studies and computational fluid dynamics.

foxsports.com wrote:“It’s the first time we’ve run the speedway bodywork and it’s pretty hard to simulate that in a wind tunnel,” Penske told ESPN.

I don't think it's "pretty hard" to simulate representative conditions in a wind tunnel; I think it's impossible. As far as I'm aware, there's no wind tunnel in the world capable of accurately modeling the effects of yaw on a car that's traveling at 225+ MPH. So, they're flying blind here.


Literally flying blind

Without end plates, as much as a third of the wing, if not more, will effectively vanish as the high-pressure stream over the wing is pulled around the tips by the low-pressure stream underneath. The wing will "shrink" from the outside in at a rate generally proportional to speed: the faster you go, the more you lose.



And while conventional wing mounts inflict a smaller drag penalty than so-called swan neck mounts, they also reduce downforce from the inside out, and they introduce a greater sensitivity to yaw, because the surface area under the wing that's blocked by them will shrink and grow and shift from side to side.


Conventional (via Mulsanne's Corner)


Swan neck (via Mulsanne's Corner)

The net result is a wing that's very easy to stall. Even if it's only minor, any sudden reduction is bad news, because it doesn't require a major loss to cause a car with ~750bhp that's being driven at the limit to break traction and spin at high speeds. A driver would need supernatural reflexes to catch that sort of snap oversteer.

(By the way, I have no --- clue why I just wrote all of this. It's overkill like using a sledgehammer to swat a fly. )

If all the conventional wisdom in the world says end plates dramatically improve the performance and efficiency of a wing, why have they removed them? I can't imagine the 1-2 kg they save is at all worth it.

And while conventional wing mounts inflict a smaller drag penalty than so-called swan neck mounts, they also reduce downforce from the inside out, and they introduce a greater sensitivity to yaw, because the surface area under the wing that's blocked by them will shrink and grow and shift from side to side.

Pretty much answered itself. It's all drag reduction. Wing mounts, end plates etc. etc. all add surface and thus, would add drag.

Exactly. End plates increase friction drag, and that can be significant at a track like IMS where the cars more or less run flat-out for the entire lap.

The problem is that it's impossible to validate the CFD results that justified the design without real-world testing, which was apparently limited, because I'm pretty sure there's currently no such thing as a rolling-road wind tunnel that generates air speeds anywhere near 225+ MPH. Windshear is reputed to be the best automotive wind tunnel in the world, and it tops out at 180 MPH.

Even CFD analysis itself can be problematic, especially when it concerns cornering flow. Remember Virgin's all-CFD design?

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First contact turn 1 Takuma Sato (-2L) and Sage Karam (OUT)... Conor Daly (OUT) oil fire in the pace lap.

11 first laps under yellow...

Wow karam was a bit blunt there in his interview...lol. i know its not classy but for some reason it makes the race battles that much more fun.

Very good race. There's no F-1 GP, not even Monaco, that can match the Indy 500 or the 24 hours of Le Mans.

It's great to see him win again. Great driver, surely deserved this after his lack of success in other series.

Going to be a good day back at work tomorrow...!

Well-earned win from JPM for sure.

I've never followed Indy but that set of highlights and the JPM win certainly looked more impressive than the Monaco GP that I (mostly) slept through yesterday!

Someone give this man a 2016 LM ride please would like to see him win the triple crown.

joseff wrote:Someone give this man a 2016 LM ride please would like to see him win the triple crown.

^ This!

hpras wrote:

WilliamsF1 wrote:

Champcar were ground effect cars, however Indy........................ not sure....

Helio's car looks like a diffuser rather than a venturi tunnel (I may be wrong)

The closest answer that I have is that F1 diffusers can't start before the centreline of the rear axle and cannot have any curvature to the bottom. The tunnel on the Indycar starts well before the rear wheel and has a curved bottom profile.

Ground effect cars- Simply as that. These venturi tunnels creates huge amount of downforce with minimum drag.. That's that's why they run very little wing on ovals. F1 should consider to reintroduce this....