Lotus E20 VD

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bhall
bhall
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Re: Lotus E20 DDRS

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gato azul wrote: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.
No worries. I don't know. But I do know that this...
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...looks different than this (the former is much smaller, and I did a horrible job selecting pictures to reflect that).
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And that this...
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...looks suspiciously like a diffuser.

I've also not discounted the possibility that cooling air is added to this system. In fact, I said that it might even be beneficial. Every car's gotta cool its engine, and that air's gotta go somewhere after it has. Might as well do something else with it, yanno?

EDIT: It should be noted that the outer edge of the VD diffuser is nearly identical to the size and shape of the non-VD vent. For that reason, I think it's safe to assume that the VD can handle both the flow sourced from the air box inlets as well as cooling air.
gato azul wrote: 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.
You've essentially just rephrased what I've said already. But, I would point out that pressure will be vented from Exit 1 first, because that vent is larger than Exit 2, and pressure always follows the path of least resistance.
gato azul wrote: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)
Again, you've essentially just rephrased my explanation. The whole point of Exit 1 is so that the duct doesn't completely pressurize. By default, that means Exit 1 will never be overwhelmed.

That said, the system's diffuser is necessary to this end, because Exit 1 would be overwhelmed without it if the vent is appropriately sized. Remember, this system must accumulate pressure before it begins to work. That means Exit 1 must be large enough to never be overwhelmed, but small enough to allow pressure to escape from Exit 2. If Exit 1 is too large, the VD can't accumulate enough useful pressure. If Exit 1 is too small, the VD can't release enough pressure to prevent the duct from becoming completely pressurized and choking. This is the pain-in-ass tuning part, getting the sizes of the inlets and exits just right.

For another angle, how about this?

Inflate a balloon and just hold the pressure in with your fingers. Apply a piece of tape elsewhere on the balloon. Puncture the balloon through the tape, and that hole will then vent pressure. Even if you slowly release some of the balloon's pressure with your fingers, the taped puncture will still vent pressure until there's none left. But, it will escape from the mouth of the balloon at a higher rate. This is the VD in a nutshell.
gato azul wrote:[...]
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".
Ambient pressure as in normal atmospheric pressure at sea level or thereabout. The pressure within the duct will be higher than ambient pressure. That said, the duct's pressure will be lower than that of the air being inducted. Inlet pressure is proportional to the airspeed of the car, and, if tuned properly, it will always be greater than that found within the duct. If this is not true, the duct cannot accumulate pressure, which is very necessary here.

I apologize if I'm mangling terms here. I'm not a trained engineer. (Can't you tell?)

Tuned properly, this system is sound as (I think) I've described it. I'm still hoping that someone with an engineering background who understands exactly what I'm saying will step in and explain it better than I have thus far.

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Cam
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Joined: 02 Mar 2012, 08:38

Re: Lotus E20 DDRS

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+1. Even if it's wrong, the work to date, the thinking behind it, the attention to detail and the fact ut has made me think seriously about what this is, needs recognition. Superb effort.
“There is only one good, knowledge, and one evil, ignorance.”
― Socrates
Ignorance is a state of being uninformed. Ignorant describes a person in the state of being unaware
who deliberately ignores or disregards important information or facts. © all rights reserved.

michl420
michl420
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Location: Austria

Re: Lotus E20 DDRS

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Raikkonen have the intakes beside the airbox but no center pillar. It looks like they found the slit in the center not effecitve and stall the wing just from the endplattes. Or it is simple not a DDRS.

MarkedOne8
MarkedOne8
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Re: Lotus E20 DDRS

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michl420 wrote:Raikkonen have the intakes beside the airbox but no center pillar. It looks like they found the slit in the center not effecitve and stall the wing just from the endplattes. Or it is simple not a DDRS.
They had to left these intakes because they can't change rool-hoop during race weekend.That would mean they are changing chassis, which is forbiden.
Fernando Alonso is the best pay-to-drive driver in F1 with the biggest amount of money behind him.
http://f1bias.com/2012/04/05/truth-abou ... nder-2008/

hardingfv32
hardingfv32
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Re: Lotus E20 DDRS

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bhallg2k wrote:That said, the system's diffuser is necessary to this end, because Exit 1 would be overwhelmed without it if the vent is appropriately sized.
1) Please expand. How does a diffuser at E1 function differently from simply having the correct size opening? Is it you claim that the diffuser brings some type of non linear function to the outlet's effective size?

2) Also, it looks like there is not a net change in the size of E1 whether the system is mounted or not. That seems odd considering the size of the role hoop ducts and E2 exit. Where is the extra flow going?

3) If the diffuser at E2 is so effective at improving exit flow, why is it not used simply to improve cooling flow by other teams that use 'cannon' exit systems?

Brian

bhall
bhall
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Re: Lotus E20 DDRS

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1. I'll explain this once more. Exit 1 must be small enough to enable the duct to accumulate the necessary pressure for the system to operate. In other words, it can't just bleed pressure on a 1:1 basis as it's drawn in. On the other hand, it must also be large enough to vent enough pressure before the system reaches its absolute maximum capacity and chokes. To fulfill both functions passively, i.e. without any direct driver intervention, a diffuser is used, and I know you know how a diffuser works.
2. Look again.
3. I have no idea what other teams are doing. But, that might not be a bad idea.

hardingfv32
hardingfv32
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Re: Lotus E20 DDRS

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bhallg2k wrote: and I know you know how a diffuser works.
I might know how the floor floor diffuser works, but I do not know how and 'why' a diffuser type shape is required at E1 in the design theory you are proposing. So, please expand on how the shape of the E1 exit plays a roll in changing/controlling the flow through E1.

Brian

bhall
bhall
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Re: Lotus E20 DDRS

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It works exactly how a "floor" diffuser works. There's no difference whatsoever.

EDIT: To expedite this whole process, why don't you tell me your understanding of the system?

hardingfv32
hardingfv32
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Re: Lotus E20 DDRS

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bhallg2k wrote:It works exactly how a "floor" diffuser works. There's no difference whatsoever.
So are you saying that the E1 diffuser is actually creating downforce at the E1 location or does it serve another purpose in your proposed system?

I am honestly trying to understand if/how the E1 diffuser modulates the flow to the E2 outlet. Why does this system require a diffuser at E1?

Brian

bhall
bhall
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Re: Lotus E20 DDRS

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No, a diffuser doesn't create downforce. A diffuser helps the floor create downforce by accelerating the air flow beneath it. In this case, the diffuser is accelerating the air flow within the duct so that it doesn't choke.

superdread
superdread
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Re: Lotus E20 DDRS

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bhallg2k wrote:It works exactly how a "floor" diffuser works. There's no difference whatsoever.
Doesn't the lower diffuser expressively use ground effect?? That's what makes a diffuser something other than a wing.
The 15cm wing above the duct opening is far far off the ground so it rather works as a wing. A wing with a heavily blown underside but still a wing (there are cuts on the side, something you would never put on a diffuser).
Last edited by superdread on 05 Aug 2012, 19:58, edited 3 times in total.

bhall
bhall
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Re: Lotus E20 DDRS

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Did this thread change again?

A diffuser extracts air pressure. That's all it ever does. Anything else is a "diffuser" in name only. Front "diffusers" are actually splitters. Front wings are wings. Ground effect acts upon the floor.
Last edited by bhall on 05 Aug 2012, 19:59, edited 1 time in total.

superdread
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Re: Lotus E20 DDRS

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bhallg2k wrote:No, a diffuser doesn't create downforce. A diffuser helps the floor create downforce by accelerating the air flow beneath it. In this case, the diffuser is accelerating the air flow within the duct so that it doesn't choke.
It does, imagine a wing close to the ground, under it is a extremely low pressure so lots lots of downforce, that' a diffuser. You don't even need a floor in front of it (front wings are diffusers, in LMP they are called front diffusers).

bhall
bhall
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Joined: 28 Feb 2006, 21:26

Re: Lotus E20 DDRS

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This is just so the thread shows a new post. I went through a time warp or something and somehow answered the last question before it was asked.

(That should count for something, I think.)

superdread
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Re: Lotus E20 DDRS

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bhallg2k wrote:This is just so the thread shows a new post. The thread went through a time warp or something, and I somehow answered your last question before you asked it.
No it didn't I put it there because I think it answers your rebuttal as well.
bhallg2k wrote: A diffuser extracts air pressure. That's all it ever does. Anything else is a "diffuser" in name only. Front "diffusers" are actually splitters. Front wings are wings. Ground effect acts upon the floor.
Ground effect works for everything close enough to the ground, thus it increases the effect of the underside of an aerofoil whichever way works. So front wings are more effective because of being near to the ground.

Let's not fight over taxonomy, but a diffuser in the form fitted to the rear underside of current F1 cars creates downforce has a low pressure in it (even lower than normal ambient pressure) so it creates a force pulling ground and car together.
(crucial for that is sealing against flow from the side, and as LMP front diffusers have that I think it is fair to call them just that)