Nose design, air curtains, undertrays, etc.

[Otto]

Starting with a clean sheet of paper and aware of recent studies of car noses with air curtains, undertrays, etc., what would an optimized car nose look like?

In other words, how best to design a nose which incorporated and optimized such features?

I bought a copy of Julian Edgar's car aero book and have watched a number of his excellent YouTube videos, which show advances by Porsche, et al, such as the 996 which intakes ram air from the stagnation point and deflects it downward so as to form a wedge-shaped air curtain to fair the flow around the front wheels. He also bolted airfoils to the front corners of his car to serve as vertical air curtains to reduce drag, and comments that proper contour of such devices can actually produce some thrust, vs. drag previously.

Why wouldn't horizontal air curtains also be useful to fair the flow up and over and down and under the nose?

So, taking such new information into account, how best to redesign a car nose to reduce drag/increase thrust? What would such nose look like?

[freebeard]

Your 'clean sheet' is dependent on packaging occupants and drivetrain/cooling.

As for the horizontal air curtain, the new Dodge Challenger has such:


cdn.carbuzz.com/gallery-images/1600/871000/700/871729.jpg

[aerohead]

Originally Posted by Otto

Starting with a clean sheet of paper and aware of recent studies of car noses with air curtains, undertrays, etc., what would an optimized car nose look like?

In other words, how best to design a nose which incorporated and optimized such features?

I bought a copy of Julian Edgar's car aero book and have watched a number of his excellent YouTube videos, which show advances by Porsche, et al, such as the 996 which intakes ram air from the stagnation point and deflects it downward so as to form a wedge-shaped air curtain to fair the flow around the front wheels. He also bolted airfoils to the front corners of his car to serve as vertical air curtains to reduce drag, and comments that proper contour of such devices can actually produce some thrust, vs. drag previously.

Why wouldn't horizontal air curtains also be useful to fair the flow up and over and down and under the nose?

So, taking such new information into account, how best to redesign a car nose to reduce drag/increase thrust? What would such nose look like?

'Best' is a very subjective value. Can't be quantified.
What drag coefficient would you be targeting?

[Piotrsko]

Taking from aircraft design, very small and pointed to reduce the square foot plate equivalent

[aerohead]

Originally Posted by Piotrsko

Taking from aircraft design, very small and pointed to reduce the square foot plate equivalent

The Prandtl/Lanchester surface of discontinuity created by the air itself creates a 'pointed' nose, as illustrated in Lanchester's 1907 text.
Since the nose is the 'least' important part of a car's body, for sub-sonic flow, the 'bulbous' nose is considered ideal. It will create the 'point' automatically, with less material, less mass, less tooling, less radical pressure gradients in yaw, etc..
'Paris Dressmakers' may dislike it.
Wheelophiles probably won't care for enclosed wheelhouses, which remain the state-of-the-art for low drag.

[freebeard]

[one minute delta]

Pointy for transonic. Bluff for moving maximum interior volume.

[Otto]

Originally Posted by freebeard

Your 'clean sheet' is dependent on packaging occupants and drivetrain/cooling.

As for the horizontal air curtain, the new Dodge Challenger has such:


cdn.carbuzz.com/gallery-images/1600/871000/700/871729.jpg

Thanks for posting, but I cannot tell from the dark picture the particulars of the horizontal air curtain. Got other pics or descriptive information?

[freebeard]

Must I do everything?

[grumble, grumble]

duckduckgo.com/?q=new+electric+Dodge+Challenger&ia=web


www.msn.com: Dodge Charger Daytona EV Concept Has Real Exhaust Noise, Multi-Speed Transmission

[Otto]

Thanks, Freebeard, that's the sort of input I was looking for but did not find without keywords including electric, etc.

Now that we have a good graphic of the nose air curtain, let's use it to pose some questions:

1. Why not also have a lower nose air curtain, to fair flow under the car's undertray so as to produce faster flow there to get lower pressure and therefore negative lift to keep the car planted via downforce?

2. Why not cant both such guide vanes forward such that they relieve the stagnation point air piled up in front of the car, but also because they're canted forward, to produce some effective thrust, as done by Julian Edgar with his side curtains of Goettingen airfloil design? In other words, use Edgar's curtain airfoil idea not just at the sides, but also top and bottom? See the video below, and ask yourself if this concept might also apply to upper and lower surfaces, thereby increasing the potential for reduced drag and increased thrust.

https://www.google.com/url?sa=t&rct=...a0M2n07TUagAwA

From Edgar's video, it appears the side curtains are ~30-40% of the total leading edge surface area where stagnant nose air has to whip around the body up, down, or sideways. He reports substantial decrease in drag and some bit of thrust from just the side curtains, so adding upper and lower curtains might double or triple the total aerodynamic benefit.

Further, NACA, NASA, and a slew of other researchers have data on suitable leading edge geometry, including when coupled with leading edge slats or guide vanes. Hoerner's book Fluid-Dynamic Drag is the bible of aerodynmicists, and discusses guide vanes on p. 3-26m noting that such vanes reduce drag on a two-dimensional body by a third to half.

Thoughts?

[freebeard]

Thoughts?

I think my head is empty, there is this constant whistling sound.

The Ferrari F12 has an external duct that bleeds air away from the A-pillar and routes it around the rear view mirror.

F12berlinetta - Focus on aerodynamics

They call it an aerobridge. www.car-revs-daily.com/2014/12/15/2014-mclaren-650s-gt3/ shows this rear view mirror without commentary:



Possibly an annular air curtain? Coanda would be proud.