Lotus E20 VD

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PlatinumZealot
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Re: Lotus E20 VD

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That is the difficultly with the the model - knowing what direction the vents are actually pointed in. There are literally hundreds of ways you can set up the model.

I have tried them at 60degrees and 45 degrees from the centre line. These positions the vents did not stall the wing even when I increased the mass flow. This is because the wake of the vent is only 6 or 7 inches across the middle of the wing and the flow it self is not really a disturbing flow - It just pulls along air flowing under the wing.

The only way to give the jet 100% coverage over the span of the wing is to have the vents shooting out 90 degrees to the flow. This I think may stall the wing... but I think the flow will be so nasty the drag will be even higher in this case. I can try it and see.
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superdread
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Re: Lotus E20 VD

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n smikle wrote:That is the difficultly with the the model - knowing what direction the vents are actually pointed in. There are literally hundreds of ways you can set up the model.

I have tried them at 60degrees and 45 degrees from the centre line. These positions the vents did not stall the wing even when I increased the mass flow. This is because the wake of the vent is only 6 or 7 inches across the middle of the wing and the flow it self is not really a disturbing flow - It just pulls along air flowing under the wing.

The only way to give the jet 100% coverage over the span of the wing is to have the vents shooting out 90 degrees to the flow. This I think may stall the wing... but I think the flow will be so nasty the drag will be even higher in this case. I can try it and see.
It doesn't have to stall the full width of the wing. The flow-vis pictures showed a wake area only in the middle third.

Maybe the length of the slits may also play a role, as stalling is kind of undercutting the min flow, the first shorter slit would separate a little bit of the flow and the second one just widens this area or prevents reattachment. If that where the case the first slot would be more important to show the principle.

hardingfv32
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Re: Lotus E20 VD

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n smikle wrote:The F-duct were blown wings that could be stalled by the driver by cutting off the flow, if I am correct. My theory is that the Lotus VD is a blown wing that is could be i)always on or ii) stalls passively... either way it is a down-force producing wing.
I have to say that I am confused by exactly how the original McLaren F-duct wing functioned. I thought flow was introduced into the slots, not removed. I do understand how removing flow from the slot could reduce down-force and drag, that being one of the theories.

So if this is the case with the Lotus system, what is the purpose of the flow from the slot in relation to the AoA and stalling? Is the wing set at a very high AoA that requires extra flow to function effectively? What happens to the rest of the wing (66% or so) not serviced by the duct? Is it operating in a stalled condition?

Brian
Last edited by hardingfv32 on Thu Sep 20, 2012 10:37 pm, edited 1 time in total.

bhall
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Re: Lotus E20 VD

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n smikle wrote:The F-duct were blown wings that could be stalled by the driver by cutting off the flow, if I am correct. My theory is that the Lotus VD is a blown wing that is could be i)always on or ii) stalls passively... either way it is a down-force producing wing.
I think gato azul and I showed that the system is both continuous and passive. But, why would they develop it to make downforce? That would mean it's just an insanely advanced monkey seat.

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N12ck
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Re: Lotus E20 VD

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bhallg2k wrote:
n smikle wrote:The F-duct were blown wings that could be stalled by the driver by cutting off the flow, if I am correct. My theory is that the Lotus VD is a blown wing that is could be i)always on or ii) stalls passively... either way it is a down-force producing wing.
I think gato azul and I showed that the system is both continuous and passive. But, why would they develop it to make downforce? That would mean it's just an insanely advanced monkey seat.
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Pierce89
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Re: Lotus E20 VD

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hardingfv32 wrote:
n smikle wrote:The F-duct were blown wings that could be stalled by the driver by cutting off the flow, if I am correct. My theory is that the Lotus VD is a blown wing that is could be i)always on or ii) stalls passively... either way it is a down-force producing wing.
I have to say that I am confused by exactly how the original McLaren F-duct wing functioned. I thought flow was introduced into the slots, not removed. I do understand how removing flow from the slot could reduce down-force and drag, that being one of the theories.

So if this is the case with the Lotus system, what is the purpose of the flow from the slot in relation to the AoA and stalling? Is the wing set at a very high AoA that requires extra flow to function effectively? What happens to the rest of the wing (66% or so) not serviced by the duct? Is it operating in a stalled condition?

Brian
I'm quite sure the 2010 F-ducts introduced a flow perpendicular to the wing to break up and seperate flow from the wing.
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hardingfv32
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Re: Lotus E20 VD

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I read that the F-duct was an attempt to mlmic the benefits of the collapsing or closing of the slot gap between the main and top element. When this technique was restricted they searched for an alternative. I assume closing the slot gap reduces flow, so then the the ducted slots of the F-duct would have to stop flowing if they were trying for the same effect.

Brian

bhall
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Re: Lotus E20 VD

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I tend to think the system worked differently than what we were led to believe in 2010.

Image

I think the flap was blown by default to keep flow attached to the damn-near-vertical rear surface, and that flow was vented through the top, hairline slot. The top part of the wing then "collected" positive pressure more like an air dam than a wing, which reduced the drag associated with wake (upwash) while still maintaining downforce all the same.

When the system was "activated," that is, when flow through the flap slot was halted, the flap "stalled," and the pressure on top of the wing was vented by way of the inlets on the main plane that fed the large, bottom slot. At that point, the rear wing was just a bluff body, which again produced a much smaller wake (upwash) than is the case with a true wing.

hardingfv32
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Re: Lotus E20 VD

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So then blow the bottom of the flap, midway between the leading and trailing edge, on the typical F1 RW will not cause stalling?

Brian

bhall
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Re: Lotus E20 VD

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Not necessarily.

Think of the upwash produced by the wing as two ribbons of air, one that flows over the wing, one under the wing. Those ribbons normally run parallel to one another, and they both produce far field drag as they pass through the theoretical Trefftz Plane.

By default, I think the McLaren solution reduced, if not altogether eliminated, the size of the ribbon flowing over the wing while still maintaining normal flow under the wing to create downforce. In other words, it made the same downforce, but only half of the induced drag.

When the system was "activated" and flow through the flap stopped, the bottom ribbon was released along with the accumulated pressure on top of the wing, which reduced or eliminated downforce and thus the other half of the induced drag. In other words, the wing "became" a bluff body with no upwash.

I think the Lotus VD has the same effect, but, due to regulatory restrictions, only on the bottom of the wing and most prominently around the center section. The duct itself splits the air flow under the wing, and as flow through the jets increases, the size of the split also increases.

Huntresa
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Re: Lotus E20 VD

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Time to necro since Lotus is running it again :D

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turbof1
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Re: Lotus E20 VD

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And quite possibly will run it in the race. Tedt Kravitz was optimistic, saying if it ran anywhere near to what it is supposed to do, it will be raced. Kimi's car seemed to be very stable, so it doesn't look like it is taking away DF at the wrong times.
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