Technology from the ceiling of spades in cars

The increase in the external form of a more efficient car to cut through the air is not a new practice; in the late 20s, the inventor Buckminster Fuller aerodynamics to public attention with his Dymaxion wild three-wheelers. Since then, designers have paid increased attention to the correlation between the air and the performance, up to Twin Peaks development with the "wing" of the racing cars of the 80s and "rationalize" the car of the 90s. roof balls are children of the 80s, and are usually more for looks than performance.

Basic Aero
The three properties of air concerning car aerodynamics are mass, elasticity and viscosity. "Mass" means the air has weight, and therefore the scale (kinetic energy) during movement. "Elasticity" means the air can compress or expand, which means it can store or release of potential energy. "Viscosity" means the air will resist "cutting" (shear), so it tend to stick to surfaces in a boundary layer before separating. This boundary layer causes what is known as the "slip" of the skin, which is the direct result of sticking to the car he is trying to get through.

Function
as soon as a car moves, the thickness of the boundary layer. The boundary layer is essentially stagnant air which acts as a kind of lubricant, which allows the surrounding air to pass without disturbance. As your car punches in the air, a boundary layer sticks to the bonnet and becomes very thick on the windshield (which is subjected to very high speed air pressure), and then suddenly thins as that it passes above the roof. roof balls take advantage of this fine adjustment in the boundary layer air in the vehicle compartment or heat exchangers.

Types
scoops come in two basic types: external and recessed. References ( "pop-up") roof Balls popularized by World Rally Racing drawing air moving rapidly past the boundary layer; they n'flow lot of air, but they also cause a lot of drag at high speed. ( "Wreck" indented), shovels, also known as conduits name NACA (National Advisory Committee for Aeronautics, the forerunner of NASA) are actually more of a scoop, but only at very high speed. Use only slow NACA ducts of the air boundary layer, so they hardly cause resistance whatsoever.

Driver comfort
The large roof scoops used on the world rally cars and race cars are usually there to provide fresh air for the driver. After all, most race cars use sealed plastic windows against the doors, and the air conditioning is not an option. Race cars often do not have the kind of marble and firewalls that prevent the motor thermal insulation of most other types of cars.

Considerations
the dynamics of other reasons for a roof scoop are mounted at the rear to cool the heat exchangers (radiators) or provide intake air for a rear collision or central engine. In almost all cases, a large NACA duct longer provide sufficient air without increasing drag, increasing the limit of the thickness of the air or cause turbulent air. Boundary layer height and turbulent kinetic energy flow not from the air, which means that less press the rear wing. In this way, too large or poorly designed roof scoop can really destroy a high-speed stability car.

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