Lotus E20 VD

[superdread]

I have been following the 2014 regs, and I have seen nothing to suggest the central 15cm rule doesn't exist anymore in 2014, and the 15cm rule is the thing that allows the monkey seats, it exists to allow wing supports (which was the intention I guess)

Also it allows the DRS pods (they sure would look stupid with 100mm radii), no way the FIA will ban that.
(Just remembered that, making my question before rather pointless, sorry.)

[Cam]

Technical boss James Allison has confirmed speculation Lotus intends to debut its so-called 'double DRS' system in Belgium next month.

On British broadcaster Sky's 'F1 Show', television pundit Ted Kravitz explained that - unlike Mercedes' pioneering device - the Lotus version is in fact not attached to the rear wing DRS.

He said Lotus actually calls it the "F-duct".

"(In a race) you can only use DRS at one point on the circuit, where they'll have this straightline speed boost at pretty much any point over 150mph," said Kravitz.

That will be a big advantage on the long straights and sweeping curves at fabled Spa-Francorchamps.

"And they (Lotus) say it's about 4 or 5 kilometres per hour (benefit) -- that's a huge advantage," said former Toyota driver and pundit Allan McNish.

Lotus has tested it on Kimi Raikkonen's black and gold E20 during Friday practice at the most recent Hockenheim and Hungary events.

And amid suggestions the entire concept will be banned by the FIA for 2013, technical boss James Allison believes it is still worth the investment and effort now.

"(Even) If it goes away next year it's still something we think is worthwhile putting our effort into," he said.

"We hope to have it ready to deploy at Spa," Allison added, insisting it will require a lot of effort to have both cars ready to race the system in Belgium.

"It's a reasonable amount of time on the calendar but in working terms not very long at all because of the shutdown," he said.

Sorry bhallg2k - they didn't like your name obviously.

edit: source (http://www.onestopstrategy.com/dailyf1n ... t+Spa.html)

[gato azul]

nice find Cam (and I mean this sincerely)
I think it shows that bhallg2k (and others) had it pretty well figured out, as far as the general principle of operation
and it's interaction (or non interaction) with DRS is concerned.
Given some "numbers" (gain in top speed) in the article, we should be able to "figure out" what kind of drag reduction
is needed to achieve this gain (not much I suppose).

Then we could carry on speculating (that all what it is - and nothing wrong with this), how the system could achieve this,
and wherever or not it will reduce downforce on the wing at the same time or not. (which would have an effect on braking capability / brake balance settings and performance (lateral) in fast corners).

Which drag, does the system reduce (aim to reduce)?
The answer to this question, maybe brings us closer to understanding how it works.
What are the components of overall drag? ( as we concern ourselfs with a aero related phenomena, we can exclude things
like rolling friction etc.)
So how does a wing (or any object) in a fluid stream creates drag?
What are the different components?

[hardingfv32]

"Television pundit", so this is where you find engineering expertise?

The Lotus duct attaches over a aero device called a 'extended fence'. It is well documented that this device is designed to create a vortex and improve flow attachment on wings at high AoA. Weakening this vortex would hurt attachment and I assume reduce drag.

So how does the flow from the strut slots weaken the vortex? Does it provide a flow that counters/upsets the normally circular flow of the vortex?

Brian

[PlatinumZealot]

THanks Harding +1.

My faith in f1 technicaL has dropped emensly. A TV pundit!

[hardingfv32]

Which drag, does the system reduce (aim to reduce)?....What are the components of overall drag?
So how does a wing (or any object) in a fluid stream creates drag?.... What are the different components?

I am up for learning something. Are we talking about induced or parasitic drag with these F-duct type systems?

I can understand how the F-duct kills lift, but could never make the connection with reduce drag.

Brian

[Timstr]

I have a few important questions for those who say they have figured out the system. I read through the explanations and these, in my opinion big questions, remain unanswered.

Is the Duct connected to the sidepods (in addition to the air channels alongside the airbox). In other words, does it draw air from the sidepods .

• -If the answer is YES, how do you reckon it inlfuences internal aerodynamics.

• -If the answers is NO, do you agree that cooling would then be compromised, as the Duct is basically obstructing the normal outlet for cooling flow through the sidepod.

The reason I'm asking these questions is because I do believe this system has an important link with the internal air flow through the sidepods, influencing internal aerodynamics, a big contributor to drag.

[Cam]

THanks Harding +1.

My faith in f1 technicaL has dropped emensly. A TV pundit!

Pity. My faith in F1 Technical is quite strong when I see fact based posts and posts that add value. My faith in individuals however is somewhat waivering. No-one asked you to take the information supplied as gospel. You should question it. Question everything. This is the exact place to do that - an open and vibrant F1 community. It was posted here as it was relevant to the topic, not necessarily as it was 100% accurate. Thats for us to discuss.

Target the information, not the forum where it was posted.

[amc]

I hope I can answer some questions:

In terms of drag, the Lotus system probably reduces form drag more than induced drag. Most of the induced drag comes from wingtips, which is why there are gills and fins in the endplates to try and reduce it as much as possible. Form drag is the 'normal' type of drag - 0.5*phi*Cd*A*v^2. An increase in top speed of around 4-5kph, means about 3% less overall drag, which means the wing itself is producing between 8 and 12% less drag.

As a result of the downforce produced by a wing, air is moved upwards, and this can clearly be seen in the flow-vis streamlines on the endplates. Looking at the pictures, it is probably moving air upwards at about 50-55 degrees to the reference plane, reducing the horizontal velocity component. The horizontal velocity will also be reduced due to skin friction, all of which contributes to a lower dynamic (and higher static) pressure behind the wing than in front of it, as in front of the wing the flow is freestream. This pressure delta, acting over the wing surface, causes a drag force.

As for lift, it works in the same way but rotated 90 degrees. High flow speed underneath a wing, and low speed on top of it, causes a pressure differential over the wing area in vertical projection, which is a lift force. Because of the angle of attack of wings, the underside also appears to be the rear side, and the front the top. Pressure conditions top-to-bottom and front-to-back are therefore proportional, and for a certain amount of lift, you will get a certain amount of drag. Sometimes (Monza) it is beneficial to reduce drag, others (Monaco) you want as much downforce as possible, hence differing wing profiles, from very shallow for low drag (less frontal area) to very deep for high downforce (high pressure differential).

If you reduce your speed, you get less downforce (lift), and less drag, but this is just one way of linking drag and speed. The Lotus 'VD' works another way:

By introducing more air underneath the wing at a certain speed, the static pressure behind the wing can be reduced (through a greater volume of air), which reduces the pressure delta front to back and therefore the drag, but also the differential top to bottom and therefore the downforce. Other phenomena - flow separation, vortices etc. can be altered or utilised to have the same effect (reducing the pressure delta).

Blown (multi-element) wings have a similar effect but that's a whole new kettle of fish that I don't want to go into now.

I don't think the duct is connected to cooling - as I think the cooling outlet is now underneath the lower duct exit at the end of the gold stripe between 'Renault' and 'Rexona' on the sidepods. So it doesn't really affect cooling that much.

[gato azul]

so by your theory, you can't reduce drag and maintain or increase downforce?
what about trying to reduce wake size (height)?

[hardingfv32]

what about trying to reduce wake size (height)?

With the F-duct type systems are we reducing or increasing the wake size?

Brian

[gato azul]

I am up for learning something.
Are we talking about induced or parasitic drag with these F-duct type systems?

I can understand how the F-duct kills lift, but could never make the connection with reduce drag.
Brian

o.k. here my attempt to make a meaningful contribution for today



think about it for a bit.

as for the other question, IMHO the attempt would be to reduce wake size
(I use the term wake, in the context of the "disturbed" flow field behind the whole car/vehicle, the volume
where velocity is not equal to free stream velocity))

....
Most of the induced drag comes from wingtip
.....

yes, but not all of it

[superdread]

what about trying to reduce wake size (height)?

With the F-duct type systems are we reducing or increasing the wake size?

Brian

They blow sideways across the wing to increase the wake of the pylon, detaching the flow.

The notion of the slots blowing in line with the main flow is rather nonsensical as the slits would have nearly no cross section (when seen from behind) and as they would have a very high energy flow would rather detach the wing than create more downforce.
Also as seen from past pictures a simple pylon has a wake not nearly as big as the one seen on the Louts (it's 1/3 of the wing after all).

[hardingfv32]

Also as seen from past pictures a simple pylon has a wake not nearly as big as the one seen on the Louts (it's 1/3 of the wing after all).

We also have pictures that show the same wake made by a wing fence, no pylon (McLaren RW). If you assume the fence was there to provide a benefit, then one could assume that such a flow pattern is not a negative. Surely no one would add a feature that produced a permanent negative performance flow pattern.

The meaning of the V-pattern on the Lotus system is not clear at this point by any means. We simply do not have any evidence to indicate wether the pattern is good or bad.

Brian

[bhall]

o.k. here my attempt to make a meaningful contribution for today

[Image]

think about it for a bit.

as for the other question, IMHO the attempt would be to reduce wake size
(I use the term wake, in the context of the "disturbed" flow field behind the whole car/vehicle, the volume
where velocity is not equal to free stream velocity))

....
Most of the induced drag comes from wingtip
.....

yes, but not all of it

I think I understand you here, and if so, I had the exact same thought while looking at Twinkies in the grocery store just now. (Don't ask me why.)

It seems to me that one of the bigger problems of the overall internal aerodynamics of the car is the fact that air is drawn in from different areas of the car at different rates relative to the car's speed. That is, the side pods draw in air at A amount per X MPH, air box ancillaries draw in air at B amount per X MPH and so on. That's to say nothing of the flow rerouting that occurs inside the car to cool electronics, oil, etc. So, it stands to reason that if the air is drawn in at different rates, it would also tend to vent at different rates. If so, that doesn't sound very efficient.

The faster a car goes, the more air it draws in, the greater the need to vent, and this is (EDIT: or would seem to be) true for all inducted air, regardless of the individual, varying rates. So, why not do it at once? What if a car had a centralized location to accept all inducted air, save for that which goes to the engine, so that it all could be vented at the same rate, one determined by a single variable rather than by many?

It seems to me that Lotus has perhaps done just that with the plenum that vents through a diffuser. That's clearly drag-reduction, just not in a way that we're accustomed to seeing.

Moreover, any slot-blowing, black-magic aerodynamic trickery would then have a source of predictable pressurized air.

Any of this make sense?