Lotus E20 VD

[bhall]

Something like this is what I had in mind.

[Huntresa]

Yeah that could work, but how would the air act in the middle of those 2 pylons ? I mean since there will be air coming from 2 sides compared to 1 side on the outer edges of the pylons.

[bhall]

It seems to me that you'd just need to make the inboard slits smaller than the outboard ones, small enough so that the vented flow doesn't overlap.

[superdread]

It seems to me that you'd just need to make the inboard slits smaller than the outboard ones, small enough so that the vented flow doesn't overlap.

They could make a slit in the wing between the pylons (would be more effective and predictable than slits in the pylon).

[bhall]

I'm not so sure about that, actually. It's the flow over the trailing edge of the main plane that must be stalled in order to achieve the desired effect, and don't think a single 15cm vent between the pylons could do the trick. It might help maybe perhaps kinda.

(This should be view upside down. Unless you live south of the equator. Then you're good.)
[youtube]http://www.youtube.com/watch?v=Ti5zUD08w5s[/youtube]

[superdread]

I'm not so sure about that, actually. It's the flow over the trailing edge of the main plane that must be stalled in order to achieve the desired effect, and don't think a single 15cm vent between the pylons could do the trick. It might help maybe perhaps kinda.

If these slits blow vertical to the wing surface you can detach the flow from it. At least that's what all the F-Ducts of the olden days did and it worked for them.

[bhall]

Old F-ducts worked with slits because they were placed just under the trailing edge of the main plane and extended pretty much from end plate to end plate, and that's simply not allowed anymore. A 15cm slit under the wing, between the pylons would have no stalling effect on the trailing edge of the main plane, because its output would be laminar by the time it reached the target.

Maybe a sit on the back of the wing could help, but I don't know that it's necessary because the duct slits already directly apply turbulent air flow to the desired area.

I could be wrong, though, and it wouldn't be the first time.

[superdread]

Old F-ducts worked with slits because they were placed just under the trailing edge of the main plane and extended pretty much from end plate to end plate, and that's simply not allowed anymore. A 15cm slit under the wing, between the pylons would have no stalling effect on the trailing edge of the main plane, because its output would be laminar by the time it reached the target.

Maybe a sit on the back of the wing could help, but I don't know that it's necessary because the duct slits already directly apply turbulent air flow to the desired area.

I could be wrong, though, and it wouldn't be the first time.

It is not strictly turbulent air you have to introduce you have to create a high pressure to overcome the Coanda effect and use a flow direction perpendicular to the main flow so that the two flows don't mix (granted, the boundary layer is turbulent).
Take the lowest point, make a slit straight down, that should detach the flow. The difference to blowing it from the side is that you need much less energy in the flow to reach detachment (a broad slow flow is easier has less energy than a thin fast one).

At least as far as I understand aerodynamics.

[Chuckjr]

Ok bhallg2k, that video was one of the most helpful wing aero explinations I've seen in my life. Thank you. Pictures are worth 10,000 words, video 10M.

Is there any way that same video type example could be used to explain your Occam's razor embracing viewpoint of the Lotus solution to overcoming wing drag? I think you really may be onto something with your idea.

There may be a major outbreak of VD up and down the pit lane soon (humor I know you will appreciate) and I'd sure fire like to understand it completely as the iterations of this come fourth.

[flyboy2160]

i don't think this VD system is going to work as you guys descibe it in the sense that it "somehow" acts passively proportionally with speed. what exactly acts passively proportionally? do you have either airflow reasoning or cfd to back this up?

remember that the engine cover "intake" air has the same free stream properties as the air approaching the wing. just as one gets higher in velocity, so does the other. so i don't see how it acts proportionally.

switching open a hole with the drs flap is another matter.

[bhall]

The v-shaped flow duct - VD - works passively in the same way wings works passively: its effectiveness is not at all dependent upon any special intervention by the driver in order to function. There are no buttons to push, levers to pull or steps to be taken. Such is how the FIA defines passive. However, if there's a better way to phrase it, be my guest.

It's proportional in the sense that it has X effect given X airspeed; the two are intrinsically linked just like any other wing, and that's the textbook definition of proportional. Again, if there's a better way to phrase it, by all means, please do so.

There's nothing especially novel about the concept behind the VD. It's the way in which Lotus has implemented it that's clever. Otherwise, we've seen similar wing-blowing solutions on the BMW Sauber F1.09 and the Mercedes W01. So, there's no mystery as to how this system works.

(And there are also no holes to be switched open.)

@ Chuckjr: I don't know how else to illustrate the VD aside from pointing to both the video I posted and the images that clearly show what this thing does, such as...



You can see where flow has been deflected, and we know that deflecting flow from the trailing edge of a wing stalls the wing.

EDIT:

(I'll come back and explain this later.)

[bucker]

http://somersf1.blogspot.com/2012/07/lo ... nheim.html

[bhall]

Ben's Guide to VD: Lotus Finally Gets a Shot



The VD consists of the following components: two intakes (white, one on each side of the air box), a duct (blue), two duct vents (red), and a diffuser (green). The purpose of the system is to shed drag/downforce without any reliance on DRS whatsoever. This system operates at all times without any direct influence from the driver, which is why it's passive by FIA standards.

Obviously, the forward motion of the car causes the intakes to draw in air. This causes static pressure to build within the duct. When the duct simply cannot accept any more pressure, excess pressure is bled through the lower vent (2) to move toward equilibrium. This action is assisted by a small diffuser that creates a low-pressure area behind the vent into which excess pressure readily migrates. The specific pressure threshold required to facilitate this action is adjustable according to the demands of the circuit.

Eventually the car reaches an airspeed in which the lower vent can no longer relieve static pressure within the duct, because that pressure is simply accumulating too quickly. When this happens, pressure is bled through the top vent (1) to move toward equilibrium. The specific pressure threshold required to facilitate this action is also adjustable according to the demands of the circuit.

Both of the aforementioned actions happen in quick succession.

It should be noted that two vents are required else the duct would very quickly become completely pressurized, and the VD would not work. The air box scoops would then be nothing more than air dam(n)s. Instead, when pressure is relieved by vent 2, the intended effect of the VD begins.

The air vented from vent 2 expands rapidly as it escapes the pressurized duct into the lower-pressure atmosphere behind the wing. The expanded air then deflects the laminar flow on the underside of the wing, which essentially is where downforce/drag is born. The specific flow targeted for deflection is that which passes over the trailing edge of the main plane. When this area of the wing is stalled it results in a substantial loss of downforce/drag, and that gives the car a higher top speed without any loss in useful downforce, because downforce effectively comes and goes as needed. As I've said before, this is a self-adjusting, stealth wing.

EDIT: It's also why I expect Lotus to have a blast at Spa and Monza. Maybe.

[Nando]

Why is there a horizontal line across the rear wing, you can see flow-wiz just under it and just over it but not next to the top portion of the main plane of the rear wing.

Could it be blowing through the mainplane wing and evenly across the top of it? hence the lack of flow-wiz in that area?

[Ral]

That VD explanation makes a bit more sense probably than anything else I've read on the topic so far. Thank you Ben

So with air venting through the main opening only, would that opening create any downforce?