Lotus E20 VD

[Matt Somers]

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

Yea that was based on mine, Scarbs and N15Cks theory from the information at hand in Hockenheim, I have since posted this based on the slotted periscope image:

http://somersf1.blogspot.co.uk/2012/08/ ... ystem.html

I'm currently scouring the Sky coverage from Hockenheim and Hungaroring to find an example where DRS is active but I think I'm on a losing battle

[bhall]

[...]

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

I'm not exactly sure what you mean by "main opening." That said, air pressure is vented concurrently from all openings once the system is performing as intended to deflect flow on the underside of the wing. It's a chain-reaction that goes from intake to pressurization to venting.

Interestingly enough, however, is that this system could easily be modified to help create downforce rather than shed it. Whether it does one or the other is just a question of how and where the inducted air is vented.

[superdread]

[...]

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

I'm not exactly sure what you mean by "main opening." That said, air pressure is vented concurrently from all openings once the system is performing as intended to deflect flow on the underside of the wing. It's a chain-reaction that goes from intake to pressurization to venting.

Interestingly enough, however, is that this system could easily be modified to help create downforce rather than shed it. Whether it does one or the other is just a question of how and where the inducted air is vented.

You mean by blowing parallel to the flow? Then you would greatly benefit from bigger slits, as they are now (narrow => high energy air), they would not be very effective. But to get real reassurement, you would at least need some mock CFD.

[Ral]

Sorry, important to be consistent in terminology when communicating with others as opposed to inside ones own head

When I said "main opening", I'm referring to what you called "the lower vent (2)" that has its own small mini diffuser.

Also, if their air intake volume supports it, there is no reason why they couldn't also have ducting leading air to the starter motor hole as well, is there? Provided also I guess though, that the additional air doesn't upset any existing airflow in that area. So I guess that's another area where perhaps it's just a matter of sacrificing potential gain for definite increased simplicity which you may have mentioned in passing

[superdread]

Sorry, important to be consistent in terminology when communicating with others as opposed to inside ones own head

When I said "main opening", I'm referring to what you called "the lower vent (2)" that has its own small mini diffuser.

Also, if their air intake volume supports it, there is no reason why they couldn't also have ducting leading air to the starter motor hole as well, is there? Provided also I guess though, that the additional air doesn't upset any existing airflow in that area. So I guess that's another area where perhaps it's just a matter of sacrificing potential gain for definite increased simplicity which you may have mentioned in passing

I rather think they blow their starter hole with the regular sidepod air, it would give them a very dependable and steady system (only determined by speed) and that's something Lotus seems to favor (e.g. with the exhaust blowing the beam wing).

[flyboy2160]

ben's guide to vd makes no sense.

[hardingfv32]

...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....

It is not clear to me why the flow only goes to the lower channel/leg of the system until it can accept no more pressure. Does this have to do with shape/design of the junction, a type of fluid switch? Is there any flow bleeding into the upper channel before the lower channel stagnates?

Brian

[PhillipM]

Probably, hence the comments from kimi over the radio previously about the system costing him some rear downforce when it wasn't setup correctly.

[bhall]

ben's guide to vd makes no sense.

I do not possess a degree in engineering nor am I mechanically inclined...

No sh|t.

...but this stuff is ain't exactly rocket surgery.


Air is drawn in from the dual intakes. It then fills the duct, increasing static air pressure within the duct. Taking the path of least resistance, as things in nature tend to do, air pressure is relieved through the larger of the two exits, Exit 1, when the duct reaches capacity. (Programme note: I've flipped the numbers of my original diagram to reflect their use chronologically.)

As the car continues to accelerate and draws in yet more air, the pressure builds to a point where the duct and Exit 1 can no longer handle all the pressure. Rather than cause the duct to explode, the pressure then follows the next path of least resistance, which is Exit 2. That exit is conveniently located under the main plane, and the pressure release at that exit then stalls the trailing edge of the main plane by deflecting the laminar flow that ordinarily flows over the trailing edge of the main plane. Hence, drag reduction.

Why not just make it all even easier and have only one exit?

Good question. The system has to be able to function with the car at top speed. Top speed means tons of air pressure. Without the ability to bleed excess pressure, the system would become completely pressurized well before the car reaches top speed. If the system is completely pressurized, it can't work, because the inlet is then, by definition, choked.

Why does it have its own diffuser?

Another good question. In order for the duct to accumulate the initial pressure required to set off the chain of events I've described, Exit 1 must be relatively small. In other words, it must release less air than the system draws in so that the duct doesn't immediately bleed pressure as it's accumulated. The problem with a small initial exit is that as the duct handles increasingly higher pressure, the exit isn't large enough to bleed sufficient pressure to prevent the system from becoming completely pressurized. The diffuser creates an area of localized low pressure behind the vent that helps to extract more pressure from the duct when the car is at or near top speed. Higher airspeed around the diffuser proportionally increases its efficiency.

You're the man! Is there anything else we should know?

Thanks. Anything else? Hmm. Only that this could also be a great way to use air that's drawn into the side pods after it's passed through the radiators to cool the engine. That would definitely add to the system's complexity. But, it could be worthwhile nonetheless.

Wait. Did you really use a picture of chlamydia in your diagram? What's wrong with you?

Yes, and I really don't know. But, don't ever, ever, ever do an image search for chlamydia. EVER!


The only difficulty with this system - aside from explaining it - is that much like real VD, this VD can be a pain in the ass. Everything I've described must happen very quickly, very orderly and, most importantly, it must happen consistently. It also has to have the flexibility to react to changing vehicle airspeeds. If any of these aspects are out of whack, this system can easily sabotage performance, i.e. it can blow when it shouldn't or not blow when it should. But, such problems can be remedied by varying the size of the various inlets and exits until the system is harmonious with the car and the circuit upon which the car is being driven.

I think the potential for VD is profound (you can use it on the front wing, too). It just might take a while to get right.

EDIT: Please be kind and attribute to me any pictures I've created (which are all edited or drawn pictures in my posts) if they are to be used elsewhere. I've got an ego to tend to, yanno?

EDIT: Someone stop me from editing this!

[N12ck]

that's basically what I described when I spoke about the passive function of my theory,

[bhall]

That's exactly what I've been describing the whole time.

[N12ck]

That's exactly what I've been describing the whole time.

which is exactley what I have been trying to get across if you read my original explanation of the passive part it is basically that

[bhall]

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.)

[Cam]

If anyone is qualified to discuss the finer points of VD, bhall2gk is your man

[PlatinumZealot]

This thread is to investigate the variable perfromance rear wing system on the Lotus E20.

Some people think it's is DRS activated (Double DRS, or DDRS), some people think it is a type of passive F-duct and then some think it is a blown wing or something else entirely.

Let's break this mystery. I guess we can start off with a few contributions from the Lotus E20 thread (you know yourself).