Lotus E20 VD

[N12ck]

That's fair enough. However, I maintain that this system is completely independent of DRS, and in that quality alone lies the true value of the system. There are no governing regulations for the VD as it's implemented here. It can be, and is, used throughout every session on every inch of the track no matter how near or far the E20 is from any rivals.

(It's possible that DRS mildly enhances the VD due to a localized area of relatively low pressure immediately surrounding Exit 2 when DRS is deployed. But, I'm not at all sure about that and such an enhancement would only boost performance by < 5% if at all.)

I simply stated it could have DRS involved to help trigger it on the DRS switch aswell as pressure driven if you extract air from when the DRS is open and duct it into the main outlet to create higher pressure within the outlet to divert more air up to the slots, although I did explain how such a passive system would work, which is what you have described like I did,

[N12ck]

Lets start this one off, my theory is either a passive system, or a passive system which can interract with DRS,

how a passive system would work:

The high pressure air is ducted down the tubes, the air can exit freely out of the rear exit above the beam wing no problem,
at a high enough speed, the pressure at the outlet is too much for the volume of air which needs to pass through it, so the air bleeds into the vertical duct and blows out of the slots.

How a passive system with DRS would work,
as above it would work the same as a passive system, however the DRS could uncover a hole like the mercedes system, which would then route air from the Endplate uncovered hole to within the ducting to blow out of the rear exit above the beamwing, increasing pressure further and causing more air to be bled and blow out of those slots in the vertical duct.

Do I believe it has DRS involved? well possibly, we will see with images of DRS open whether that theory is correct, however it would work the same way as a passive system and would still work as a passive system

Bhallg2k has some nice diagrams of this same 1st paragraph which we agree on,

[Jackles-UK]

Just so I can get something understood in my head!

Very simply, is it fair to assume that as the airflow under the wing accelerates (with track speed) that rushing air 'sucks', for lack of a better expression, the intake air up into the duct - rather than going down below the beam wing? Like a straw in a cup of water?

If that is the case and it is a passive f-duct type device I can't see them making it allowable for next year. I thought the main reason for banning the 2010 shark-fin style engine covers was a way to stop the use of f-ducts once and for all but, even though Lotus have engineered an ingenious and elegant way of circumnavigating the rules, the effect is still there. Plus, like some have mentioned previously, if it is kept for next year teams will inevitably push the envelope to see what else can be stalled in this way (I can just see the rumours of a McLaren Octo-VD now!!) leading to gigantic R&D costs.

Shame, mind.

[hardingfv32]

What would restrict the flow only to the lower branch during the time period before it stagnates? Why would flow not go into the upper branch?

Brian

[bhall]

Nothing restricts the flow, and such flow does happen. It's just not useful until it reaches a certain pressure, which only happens after the rest of the duct reaches a certain pressure.

[N12ck]

Nothing restricts the flow, and such flow does happen. It's just not useful until it reaches a certain pressure, which only happens after the rest of the duct reaches a certain pressure.

Which is tuned by the size of the outlet above the beam wing

[hardingfv32]

Is there some thing, fluid switch, etc., controlling the flow? How would you describe its design for me to research?

If there is no control, then why wouldn't the upper and smaller channel stall first or at least at the same time?

Brian

[bhall]

[...] How would you describe its design for me to research?

If there is no control, then why wouldn't the upper and smaller channel stall first or at least at the same time?

You're kidding with that first bit, right?

It's the series of progressively smaller exits that controls the flow.

[hardingfv32]

Sincere question: Why isn't flow to the different size outlets just proportional? A simplistic view would have the smaller outlet stalling/backing up before the larger outlet.

I understand what would be useful as a system, but I just do not see the correct parts being discussed.

Brian

[bhall]

The flow through the vents is proportional; it's proportional to the size of the vent. Keep in mind that this entire system must be pressurized higher than ambient to work.

[hardingfv32]

If the flow is proportional then, then why do a number of you think that the lower channel will stagnate before the upper (smaller) channel?

On a more basic theme, why was this not done years ago? Hasn't Lotus implied that this system is DRS related?

Brian

[bhall]

I guess this was split off because the E20 is such a hotbed of innovation that the normal thread couldn't possibly contain anything more.

And, by the way, the system being discussed is not DDRS. The novelty of the system is precisely because it has nothing to do with DRS. In fact, I'd like to see someone explain how it could even work with DRS. The more I think about it, the more I realize that DRS is likely an impediment to the VD's operation.

If the flow is proportional then, then why do a number of you think that the lower channel will stagnate before the upper (smaller) channel?

On a more basic theme, why was this not done years ago? Hasn't Lotus implied that this system is DRS related?

Brian

For the system to work, it must always draw in more air than it vents; it needs positive pressure. For all intents and purposes, the entire system becomes pressurized at about the same time. My explanation just breaks down the path of pressure release.

The size and type of vents it employs are what enables the system to maintain positive pressure while providing useful pressure release at Exit 2 to stall the trailing edge of the main plane. Everything is based around that.

I imagine this wasn't done before now because getting this right will be a pain in the ass, and the benefit relative to the amount of work involved may not be that big. But, the rules are so tight these days that teams are forced to go a thousand miles to gain a few tenths.

[gato azul]

For the system to work, it must always draw in more air than it vents; it needs positive pressure. For all intents and purposes, the entire system becomes pressurized at about the same time. My explanation just breaks down the path of pressure release.

The size and type of vents it employs are what enables the system to maintain positive pressure while providing useful pressure release at Exit 2 to stall the trailing edge of the main plane. Everything is based around that.

While I agree with you general line of thought bhallg2k, I'm not quite sure, you need what you call "vent 1".
This vent, as on the RB car and some others, has been there before, independent of the VG system.
Yes, it did look a bit different and did not sport this profile (diffuser?) around, but this opening has been there since the
beginning of the season.

So why not just link the openings (ears) around the the engine/airbox intake direct with your vent/exit 2 (VD exit) in the center pillar and be done with it?
You could tune the size of the intake to get the pressure (differential) you want need - no?

what do you think is "mission critical" for the system to work ?
the exit velocity of the air when blown out of the slits in the center pillar? (this is how I understood you, but just wanted to double check), the flow rate or both?
Because if you create positive pressure in the duct, you will spill air around the intakes as well - IMO, and I'm not sure, that is what you want to see.

[bhall]

Exit 1 is different than the so-called "cannon" vents found on Red Bull and other cars, including the one previously seen on the E20. Those vents release air that's been inducted from the side pods for cooling. Exit 1 allows the VD to maintain positive pressure, relative to ambient, without the duct becoming completely pressurized and unable to accept more air flow. The ability to accept flow at all times is crucial, otherwise the inlets choke and become veritable air dams.

That said, the VD only has positive pressure relative to ambient pressure. Relative to the pressure at the VD's inlets, the VD has less pressure.

This is the part where I'd really like someone with an in-depth understanding of the equations and nuance of static and dynamic pressure to step in and explain all of this in terms the engineering crowd will understand. Despite the clarity with which I see the picture in my head, I evidently cannot convey it properly.

[gato azul]

Exit 1 is different than the so-called "cannon" vents found on Red Bull and other cars, including the one previously seen on the E20.
Those vents release air that's been inducted from the side pods for cooling.

How do you know? - Sorry mate, I don't want to come across as argumentative, but I think it is fair to assume, that there is still a need to went the air from the side pod intakes somewhere, otherwise we would need to see other outlets, if you would like to use Vent 1 exclusively for your VD concept.

Exit 1 allows the VD to maintain positive pressure, relative to ambient, without the duct becoming completely pressurized and unable to accept more air flow.
The ability to accept flow at all times is crucial, otherwise the inlets choke and become veritable air dams.

Yes, I do 100% agree with your second sentence, therefore I do not think, that you would like to have positive pressure in the whole system, back to the intakes otherwise, you would just create massive drag, and would not be able to have enough airflow for cooling (the air from the sidepods/radiators which IMHO still needs to exit via Vent 1/Cannon style)
In this context, I feel that this image of yours (the 2nd one), is perhaps a bit misleading:



How about this:
The intakes (ears) around the airbox feed directly the VD slots (Vent 2), if the snorkel/center pillar part becomes saturated, all excess air is vented into the cannon style center exit (Vent 1), to ensue, that you have maximum airflow through the inlets at all times.
The excess air joins the air which comes from the sidepods/coolers anyway in is released into the low pressure zone behind the car, helping to reduce drag a bit along the way.
The element/diffuser around the exit (vent 1) helps to extract the extra portion of air, which comes from the "ears" in addition to the normal air which comes via the sidepod/radiators.

I do agree with you about the primary function of the VD (vent 2) and how it will affect the airflow around the wing, but I think that the sequence is the other way round, and that you never exceed the capacity of vent 1 to make vent 2 (VD) work.
Vent 1 will just "vent" any excess air which vent 2 (VD) can't handle, to ensure that you don't choke the intakes (ears).

That said, the VD only has positive pressure relative to ambient pressure.
Relative to the pressure at the VD's inlets, the VD has less pressure.

not quite sure what you mean by this.
Sure you need a pressure differential, otherwise you won't have any air flow, but I'm not quite sure about your definition of "ambient pressure".

I can be wrong of course, wouldn't be he first time, nor will it be the last.
On a side note:
I think Hollus argument/mentioning in regard to a negative effect on braking capability still stands, independent of the fact if this system is switched on/off or "self adjusting".
At top speed you will have less drag, which would have help braking, and due to the lesser rear downforce you can't use the same rear brake force/torque/pressure as with higher downforce, so brake balance most likely would need to be adjusted to account for this.
I don't think, that it is a big deal, just a matter of "can't have your cake and eat it", so need to keep it in mind.
The positives probably outweight the drawbacks.