Larger Downforce Near Ground

[kach22i]

Larger Downforce Near Ground
Vehicle Aerodynamics


How can this be?

I can understand an aircraft landing in ground effect, which squishes and compresses the air between the underside of the wind and or body thereby getting more lift.

However, an inverted wing close to the ground getting more downforce?

How can this be?

Will the air on the underside be accelerated even more when air flow is squished via Venturi effect when in close ground proximity?

[Recumpence]

Assuming the rear of the vehicle (ground clearance at the rear) is greater than the front, a vacuum affect is created under the car. The venturi affect you asked about is part of the affect as well. This is something we did alot of reasearch on when doing ultra high speed competition with RC cars. These affects are exadurated on a small car at 100+mph speeds. These theories are easy to put to the test with our small cars.

Matt

[gone-ot]

...anybody remember the old science experiment where you blow air through the center of a wooden thread thimble and it "holds" a sheet of paper tight against the bottom of the thimble (there's a pin stuck through the paper which protrudes up and into the hole in the wooden thimble)?

It's the same idea, only horizontally instead of vertically...

[niky]

This is also the same reason why it is dangerous for two ships to pass too close to one another.

[kach22i]

Originally Posted by niky

This is also the same reason why it is dangerous for two ships to pass too close to one another.

Yes, that is an excellent example.

Water can be displaced, but does not compress.

The displaced water off to the sides could compress the hull of an adjacent ship.

I'm sure some of the water would just splash upward along the ship sides, and some reflect off the bottom of a river. However that space in between could be dangerous indeed.

[niky]

It's more that the suction effect pulls the ships closer together. And not just ship to ship. Ship to shore, ship to channel bottom, etcetera... whenever there's a narrow channel between the ship and another body, the suction effect pulls the ship closer to said body.

[kach22i]

Originally Posted by niky

It's more that the suction effect pulls the ships closer together. And not just ship to ship. Ship to shore, ship to channel bottom, etcetera... whenever there's a narrow channel between the ship and another body, the suction effect pulls the ship closer to said body.

Fascinating, I now wonder if a hull could be be shaped and designed to be replant or at least mitigate the suction forces.

I do know that boats/ships are more buoyant in shall water verses deep water. In fact it's pretty much a mystery why very deep water is less buoyant.

This suction thing must be something which happens at very close proximity.

[aerohead]

The wing's underside,and it's mirror image below the ground form the Venturi which functions according to Daniel Bernoulli's principles of pressure and velocity.
The near ground wing sequesters a volume of air which cannot escape,and it is accelerated to high velocity and very low pressure to induce the downforce.
In 1992,the Williams Grand Prix Engineering folks,with low/high F1 wing setup,were achieving 3,500-lbs downforce at 150-mph with a 1,500-lb race car.

[euromodder]

Originally Posted by kach22i

However, an inverted wing close to the ground getting more downforce?

How can this be?

Venturi & Bernoulli

If you lower the inverted wing and keep the wing's speed constant, it needs to get rid of the air through a proportionally ever narrower opening.
[the wing's camber is getting ever more important compared to the remaining opening]

This can only happen by increasing the speed of the air even further beyond that of the vehicle, and further lowering its pressure.
This makes the wing more effective at the same vehicle speed.

[kach22i]

Great information, thanks to all.

I had an idea once where the rear axle of a car/truck would be foil shaped, and designed to produce down-force.

This assuming a smooth under belly for the vehicle of course.

I'm now thinking this idea could have wings, or at least inverted wings.