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By bending the rules of aerodynamics, automakers can create low-drag cars that slice through the air, which in turn help improves efficiency.

30 Dec 2014 | Category: Car Technical Advice

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By the time a spacecraft leaves the last layer of Earth's atmosphere, it no longer needs to be streamlined, because out in space there is very little air to provide any resistance. In fact, there are so few air molecules way 'up there' that even the sun's rays have nothing to reflect off - which is why outer space, as we know it, perpetually appears to be night.

The power of air in motion can be illustrated by how wind can propel sail boats

The air down here on Planet Earth consists predominantly of nitrogen and oxygen, with an average density of 1.2kg per cubic metre. That's enough to reflect light and, yes, enough to create 'buoyancy' for aeroplanes to fly on. It's also enough to
impede motion - an effect better known as aerodynamic resistance.

Air-ssentials 

Air, like any gas or liquid, is technically classified as a fluid because it can flow over, below or around a solid object. In
extreme conditions, fast-moving air (or a 'full-blown' wind) can exert a tremendous force. That it can propel a sailboat illustrates the power of air in motion.

Wind resistance and the behaviour of air around a moving car are critical aspects of automotive design, because they affect fuel economy, driving stability and cruising refinement. Motor vehicles, of course, travel on terra firma, but they still have to move through air. Any object moving along is opposing forces exerted by air, which increase as the speed of movement rises. 
The laws of physics have defined the drag (or resistance) due to air to be proportional to the square of the speed. What this means is that if the speed is doubled, drag increases by four times (i.e. 2 x 2), and if speed is tripled, drag increases by a factor of nine (i.e. 3 x 3), and so on. Drag consumes kinetic energy and compromises the car's efficiency.

Air-bracadabra 

There are still plenty of unknowns that surround the scientific analysis of moving air. The underlying reason is that air, though gaseous in state, is nonetheless a fluid. In its worst form, such as a hurricane or a tornado, moving air has enough power to uproot trees and devastate buildings. Even today, the physical predictability of wind remains a dark science.

Moving air has enough power to uproot trees and destruct buildings

There are very few 'magicians' who know exactly how air behaves (or misbehaves) over a moving object, and they are somehow able to manipulate said behaviour. One of them is Adrian Newey, Red Bull F1's chief engineer and possibly
the world's top automotive aerodynamicist.

That Newey's scalp is devoid of any turbulence-inducing hair might not be a mere coincidence!
Torque The article first appeared in the April 2013 issue of Torque. Log on to their website to subscribe.
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