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Old 07-05-2022, 11:59 AM   #11 (permalink)
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winglets

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Originally Posted by serialk11r View Post




No what I was trying to get at is you would have to do a lot of cutting into most cars to get flying buttresses, so I was wondering if the winglets alone do anything, or if just the piece perpendicular to the window that forms the root of the winglet would have a similar effect.
By 'winglets' are we talking about the roof extensions, extending along the roof contour, as would happen, had Lotus just put a 'Kamm'-type roofline?
Combined with the pop-up spoiler, air coming around the rear pillars is captured under the over-gang, where vortices might have formed.
The vortex pair would have created induced rear lift and drag.
The overhang and spoiler conspire to kill the lift and drag both.
By not doing a Kamm-back, the driver probably has better rear outward vision. Less blind spot.

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Old 07-05-2022, 12:30 PM   #12 (permalink)
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drag

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Originally Posted by kach22i View Post
On some of my roof wing studies (link in signature below) you once suggested roof cab outer corner treatments (various forms studied) would at best "delay" vortex formation.

If the case here is one of vortex delay, that would mean swaths of air swishing sideways/diagonally over the rear window may be avoided, but the drag would be still trailing the vehicle.
Pickup cab roof extensions, combined with a 'wing' allows pressure recovery, both in elevation and plan.
Both help direct flow towards the wake.
With a half-tonneau, the captured vortice is enhanced to the good.
With the Lotus, I'm guessing that they want good rear outward vision.
Leaving the center 'open' would provide for downwash which would flush air into what might otherwise be a 'squareback' wake full of back-soiling dust obstructing the vision.
Rear lift must be an issue, hence the pop-up spoiler. Should bistable flow exist, the rear spoiler would burst it.
The overhang and spoiler act kinda like fences to direct transverse flow into this area from the sides to purge dust-entrained air.
You can't get low drag, as there's no surface on which the flow can decelerate and gain pressure. As with a Kamm-back.
If Lotus wanted low drag the car would look more like their GT concept.
The Eletre is just some compromise. It's an SUV.
Maybe not as bad as a Chevy Malibu Maxx, but not as clean as a Malibu sedan.

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