Active aero

[Tommy Cookers]

blowing the wings should work just fine for driving in another car's wake
it increases the DF coeff without any increase in AoA or wing etc geometry
by increasing the circulation around the (unchanged) wing etc it can boost lift/DF coeff by up to eg about 50%

the blowing could be actively DF controlled eg to maintain or boost wing DF coeff regardless of wake severity
maybe the blowing gas would be more efficiently used on the wings rather than eg on the diffuser

the blowing gas could come from the induction side or the exhaust side, and its use would tend to be self-rationing
guessing - a not unreasonable amount of gas would be needed in this rather limited use ?

[livinglikethathuh]

True, but engineers would consider that too so they could minimize or even take advantage of those modified airflows depending on the configuration, couldn´t they?

Anycase active aero is a very open term wich may include a lot of devices. Probably allowing all of them wouldn´t be a good idea, but allowing some specific device wich could solve some problems without messing the rest of aerodynamics too much

I meant the case where active aero is deployed akin to DRS, i.e. when only close to another car. If we use active aero throughout the entire race, it would actually improve the integration aspect but that's not the point I meant.

There's already an active aero system on the rear wing, DRS, and it does the job well enough.

If you only consider overtaking numbers, then yes, it works flawlessly. But some people like myself think it only make up the numbers, but ruins the real battles because it do not allow closer racing (diry air problem in corners remain the same) and provide an advantage in straights wich means drivers don´t need to be agressive to overtake, just wait to the straight and pass him easily.

[/quote]

I knew I should have explained that further. The purpose of DRS is to reduce drag, and it does that pretty well without many consequences. The impact of racing is another subject.

[bhall II]

blowing the wings should work just fine for driving in another car's wake

I considered that, too. But, it doesn't solve the issue of reduced force enhancement due to weakened end plate vortices. That's largely a function of air flow over the wing and cascades, and it's apparently easily disrupted. (It's also where the majority of front wing development seems to be taking place these days.)


This data is mostly irrelevant. I just wanted the picture.

Increasing rear downforce is far easier, but that doesn't help the biggest problem, which is understeer.

It will depend on how do you define equitable and artificial.

I hate DRS as much as anyone. It's frustrating to watch a driver put on a masterful display of defensive tactics - somehow nailing every apex while making his car wide as hell at the same time - only to have the trailing car blow right by him in the next DRS zone. To me, it's arbitrarily deciding who gets the advantages of air and who gets the disadvantages of air without regard to the simple fact that air is an intrinsic part of life on Earth. It never mattered before; why are we saying it matters now?

That much, though, is subjective in my view. Other parts aren't.

Despite DRS, rapidly-degrading tires, and a refueling ban - all measures taken to increase overtaking - the sport is in the midst of the sharpest decline in overtaking in the last 35 years.

Evidence suggests the decline is the result of a convergence of design philosophies that make it difficult to exact enough of a performance differential to regularly facilitate overtaking. This happens in (mostly) spec-series, too.

Much like F1, IndyCar features many laps of drivers holding station until pit stops shuffle the order. (Click each to show full lap chart.)


First race of the 2015 IndyCar season


Last race of the 2015 IndyCar season

It seems the issue isn't aerodynamic as much as it's a structural problem inherent to any discipline that begins a race with faster cars/drivers ahead of slower cars/drivers on circuits that can generally only sustain a single racing line.

Back to subjective: I'm not at all suggesting reversed grids or anything of the sort. I just question the legitimacy of making (expensive) changes that are only likely to have temporary effects until convergence reigns it all in again. I see it as a perpetuating a boom and bust cycle that doesn't serve any long-term goals.

The end result of every change previously made to increase overtaking is a series most people don't seem to enjoy, and, again, it's one in which overtaking is in serious decline.

I'm by no means an expert, but I was thinking about the floor regulations as we have now, but with retractable side skirts. In normal mode these are retracted and the floor dimensions are exactly the same as now, but when running withing 1s at the end of a straight, they would be deployed and close off the sides of the floor.

Sealing the floor is generally only helpful with a highly cambered surface, like a venturi tunnel, that leads to a large exit downstream.

Due to heavily restricted diffusers, which limit underbody performance, current philosophy seems to treat the leading edge of the floor and barge boards almost like a wing (think of the sidepod turning vanes as end plates) that torques the floor and dispenses with a great deal of air flow before it ever gets to the diffuser. If that's in fact the case, side skirts would reduce downforce and increase drag, because it would send more air flow to the diffuser than it can handle, creating a bottleneck that restricts everything in front of it.

[Andres125sx]

Bottleneck at the difusser? How´s that posible when a diffuser is exactly the opposite?

And rake increases this effect?


Probably I´m missing something in your explanation, but if movable skirts would be allowed, I´m sure they would improve downforce, not reduce it.

I think you sometimes think too much about how current rules would make imposible to apply some changes, instead of thinking about what changes would be needed to make that possible.

If we´re looking for options wich would improve racing, we can´t focus too much on current rules, they´d need several changes obviously

Edit: almost forgot it, thanks for that link about the floor, it´s great and really helpful =D> . Specially for a non native english speaker like myself, now I know the name in english of all those parts.... even when I don´t know the name in spanish of many of them

[mrluke]

Theres only so much air that the diffuser can process especially as its size is heavily restricted.

Once you exceed this then it will become a bottleneck.

[bhall II]

EDIT: mrluke beat me to it. (You wouldn't happen to be a Bond villain's main henchman, would you?)

I guess I should have said that adding skirts would make the existing bottleneck worse.

Yes, there's a bottleneck.

Along any flat floor, viscous losses cause air flow to slow down (blue crescents below) as it moves away from the energizing influence of the floor's leading edge (red areas adjacent to the plank) until it reaches the re-energizing effects of the diffuser.


Velocity gradient

This occurs because the diffuser has a limited capacity, and it's currently too small to move air flow at the same rate it's introduced under the floor (and it has been for decades, notwithstanding double-diffusers). To be efficient, it would need to be roughly as wide as the floor's leading edge.

To combat this, teams use barge boards to redirect air flow diagonally across the leading edge (you can see this in action in the last image on my previous post). This has two effects: it reduces the bottleneck by reducing air flow to the diffuser, which increases overall efficiency, and it also moves the center of pressure forward (seen below), because it basically turns the front of the floor into a wing.


Pressure gradient

You can see the vents, or whatever they're called, that are used to aid the effect. The leading one even has a gurney flap...



If you were to drop side skirts, you'd just be collecting air flow the diffuser can't handle, and that would increase pressure. In other words: it would be an air brake.

Beyond that, increasing diffuser efficiency isn't exactly the first place to look when it comes to solutions for "dirty air." It can certainly help in some ways, but it needs to be allied with something at the front of the car. Otherwise, it would just move the car's center of pressure rearward, which would induce understeer.

(Adding rake somewhat helps on one front, because it pushes the t-tray closer to the ground, and that further reduces air flow under the floor. But, the main goal of adding rake is to lower the front wing in order to enhance ground effect. The trade-off is reduced diffuser efficiency due to increased ride height.)

I think you sometimes think too much about how current rules would make imposible to apply some changes, instead of thinking about what changes would be needed to make that possible.

There's some validity to that. But, I think it's less about me looking at the current rules and more about me trying to see the big picture. Some things just are, and there's not a whole lot we can do about it.

If the goal is to eliminate the effects of "dirty air," the solution is very, very simple: get rid of the wings, and the problem's solved. You're gonna lose A LOT of speed, though.

As much as it's derided, aero really is where the speed lives. Engineers know it, and they're never gonna forget it, because their job is to make the cars fast, and nothing else. That means there will always be increasing amounts of "dirty air" as they steadily reclaim losses inflicted by any moves to decrease "dirty air."

To counteract that is somewhat akin to this...


Good luck

[Andres125sx]

Great explanation, upvoted, thanks

So the problem is with current diffusers that simply are too small, with true venturi tunnels all along the floor it would be different I guess

(Adding rake somewhat helps on one front, because it pushes the t-tray closer to the ground, and that further reduces air flow under the floor. But, the main goal of adding rake is to lower the front wing in order to enhance ground effect. The trade-off is reduced diffuser efficiency due to increased ride height.)

That´s exactly the reason I proposed some posts back variable ride height in the front (with active suspensions obviously) to move the front wing closer to the ground when in dirty air, and improve ground effects

It would be some sort of DAS as we´ve been discussing earlier in the thread, but instead of increasing AoA, reducing wing height. Could that help compensating part of the DF lost when in dirty air?

If the goal is to eliminate the effects of "dirty air," the solution is very, very simple: get rid of the wings, and the problem's solved.

Too easy, where is the challenge in that?

[bhall II]

Given the topic of conversation, it's perhaps somewhat ironic that the main reason why diffuser efficiency has been made to be so pitiful, especially recently, is to reduce "dirty air."

And the problem with relying on reduced front wing ride height to counteract "dirty air" is that it doesn't address the loss of air flow over the wing.

Teams are increasingly using cascades and complex wing tips to increase the strength of the end plate vortex, because it provides a significant increase in downforce.



The various cascades and turning vanes direct air flow over the end plates, which is then pulled under the wing by the end plate vortex. That rotation then creates an enhanced upwash along the suction surface of the wing, generating additional downforce. I'm not sure reduced ride height alone can replace that.

There's stuff like this all over the car that gets disrupted while traveling in another car's wake.

[trinidefender]

Bhall II the problem with your theory is that a few years ago there was a team that added skirts in the windtunnel to see how what the effect would be if they totally sealed the floor. They discovered the he downforce was increased significantly. The original purpose of this research was to see how much downforce they can recover by improving floor sealing in whatever fashion. I.e. Trying to discover where the largest gains are for future development in their car.

If your theory was correct then they would lose downforce. I'm not even sure where I read this, I'll attempt to find the article but make no promises.

I'll also dispute how the vortex around the endplate of the front wing increases downforce. It may aid in some way to help control airflow around the front wheel which increases downforce however I will get that it doesn't directly increase downforce as a result of increased upwash.

Simply look at a plane wing. All the modern designs are moving toward the use of raked wingtips, increasing the aspect ratio, increasing washout at the tip, vertical tips etc all in an effort to decrease wingtip vortices.

[Just_a_fan]

Simply look at a plane wing. All the modern designs are moving toward the use of raked wingtips, increasing the aspect ratio, increasing washout at the tip, vertical tips etc all in an effort to decrease wingtip vortices.

Aircraft wings are all about cruising efficiency, improving mpg effectively, because they are free to alter the wing to improve lift at critical times e.g. take off. Whilst efficiency is important in F1, it's only important in terms of L/D. On some circuits such as Monaco, efficiency is irrelevant.

[trinidefender]

Simply look at a plane wing. All the modern designs are moving toward the use of raked wingtips, increasing the aspect ratio, increasing washout at the tip, vertical tips etc all in an effort to decrease wingtip vortices.

Aircraft wings are all about cruising efficiency, improving mpg effectively, because they are free to alter the wing to improve lift at critical times e.g. take off. Whilst efficiency is important in F1, it's only important in terms of L/D. On some circuits such as Monaco, efficiency is irrelevant.

And your comment is completely nonsensical. The part you seem to be missing is that the larger a vortex you have rolling around the wing tip the less useful surface area of wing that you have. The airflow moves from the high pressure side of a wing to the low pressure side. This means that the pressure differential between the low and high pressure sides of the wing is less. Ergo less lift (or downforce in our case)

To add further evidence to my previous post. For a while up until the front wing bending rules were tightened up extraordinarily, Red Bull were the masters of designing a front wing that has the outer sections bend so far down that in some cases they touched the ground. By his logic this would decrease downforce yet it doesn't. This was a feature built into the wing to increase downforce by helping to seal off the bottom of the front wing at the sides.

The end result is that the yes with the addition of outer cascade elements there will be a stronger vortex rolling around the endplate. However with the wing flexing it helps to stop this airflow getting underneath the front wing. The stronger vortex is then used to help control front wheel tyre wake. On the bottom of the wing there is a vortex tunnel, this (in an ideal world and perfect wing) creates its own separate vortex that then joins the endplate vortex to control tyre wake. By controlling front tyre wake you help to create downforce on the floor of the car increasing downforce at both the middle and rear end of the car and if don't right, may decrease drag.

People love to talk about vortices etc and how they do this and that however there are a few main places they are used. Controlling front tyre wake being one of them. I believe a lot of people don't understand the importance of it. If you don't believe me then check how many new front wings that teams introduce during a season. Then check how many of the the new versions have incremental changes to the outer portion of the front wing. I.e. The portion that controls airflow around the outside of the front tyres.

[bhall II]

Bhall II the problem with your theory...

I'm interested to see any material you have about sliding skirts on flat floors. But my theory about front wing vortices isn't my theory; it's experimentally confirmed at least here and here.

From the former:

EDIT: Oops.

[trinidefender]

Bhall II the problem with your theory...

I'm interested to see any material you have about sliding skirts on flat floors. But my theory about front wing vortices isn't my theory; it's experimentally confirmed at least here and here.

From the former:

http://i.imgur.com/b9bvJtt.jpg

Check the addition to my post above.

Edit: I shall go more in depth hopefully tomorrow but one of the last sentences says that it reduces the incidence angle and increases upwash. This means that it effectively reduces the angle of attack on that portion of wing as the airflow is moving in a more vertical vector (horrible description). When you reduce the AoA of a wing you reduce the pressure differential reducing downforce. I believe you have misunderstood that. I'm also interpreting those paragraphs to mean something different to yourself.

Edit No. 2: Note, I never said their was no vortex underneath the front wing. Quite the opposite actually. I said that in an ideal world there is also a vortex on the top and around the endplate and underneath front in the vortex tunnel (which you see teams using more and more these days especially since the maximum width of the front wing was reduced). Sometimes the top vortex feeds into the lower vortex, something one of your graphics seems to illustrate.

[bhall II]

Read all the information I've provided before you draw any conclusions based upon it. You might be surprised.

(EDIT: I just realized I totally screwed up that cut 'n paste job above. So, that much is my fault. The relevant sections here, in addition to the mess I posted, are 4.4 through 4.7.)

If I correctly understand your Red Bull flexible wing postulation, you're saying the team designed a front wing that goes above and beyond to create peak downforce, thus peak drag, along straights, where downforce is unnecessary and drag is a hindrance? After all, that's where wing flex was at its maximum.



Or does it make more sense to take what we've learned from the Zhang study that details how vortex breakdown below a certain ride height leads to force reduction, thus shedding induced drag, to assume that maybe Red Bull used variable ride height wing tips to run more downforce than would otherwise be competitively feasible without an ability reduce drag along straights?





Vortices don't reduce the "useful surface area of wing that you have" for two reasons: there's an end plate, which is actually somewhat unnecessary for that effect...



...and because the upwash created by the vortices along the suction surface keeps air flow attached that what would otherwise become detached without it. The effect is almost like that of a slot; it's just coming from somewhere else.

You have to reorient your thinking to the relevant boundary conditions.

[turbof1]

Ehm, Bhall: the indy car you showed actually had an endplate at the beginning of the season. It was actually forbidden when too many endplates with cascades broke off. I would not inmediately call it unnecessary.