When we think of aerodynamics the first thing that usually comes to mind is the construction and design of planes. Their bodies are specifically designed to produce lift by wielding the rushing air as a tool and changing its direction of flow. Aerodynamics are also crucial when designing much smaller remote-controlled planes and helicopters, where the slightest gust of wind is capable of knocking them out of the air mid-flight.
But the science and application of knowledge related to positive uses of aerodynamics on a chassis are not just limited to flying machines. Land and even water vehicles use this as well. As air is present everywhere on Earth, even ships and boats have to account for drag force and shape themselves such that they cut through the wind as best as they can. Whereas racecars have their bodies designed so that the air flow is beneficial to their acceleration as well as helping them maintain a higher top speed. But how does aerodynamics help your average everyday car in its function during slow and methodical city driving?
What is Aerodynamics?
First of all, aerodynamics is the study of not just air, but its movement and how this particular movement is affected by the presence of an object that in some way obstructs the direct motion of air through a space. This field of science, though having been known about for millennia, was only properly begun to be studied and experimented with in the 18th Century.
Before that time the concept of drag forces being felt due to the presence of air did exist, but was barely touched upon by men of science. Sir Isaac Newton, famed for coining the Theory of Gravity and the Laws of Motion, was in fact also the first aerodynamicist of the world; due to also being the first person to suggest the theory of air resistance. Further work and studies were then carried out on this concept so that flight of objects heavier than air could be achieved.
Aerodynamics doesn’t just study how the motion of air through a space is affected to due to the presence of objects in its way. It also studies how this motion can be altered to achieve something that would be difficult to do without utilizing the help of aerodynamics. Flight in particular seems impossible without positively utilizing aerodynamics on a plane’s body in some way or another.
Drag Force on Cars
Before we cover how cars use aerodynamics to function better on the roads, let’s talk about one of the most basic principles of air and how it affects the movement of cars, necessitating the study and use of aerodynamics to help the car move more efficiently. This principle is what we mentioned above; the air resistance and drag force applied on an object moving through air.
Whenever an object moves through air, it experiences air resistance in the form of trillions of air molecules colliding with the body of said object. And the smaller and lighter the mass of this object, the more successful air is at stopping this object. This can be proven by a very simple experiment; drop a feather and a brick at the same time. The brick falls much faster, whereas the feather gently glides along the air due to the air resistance combatting its extremely light weight quite efficiently. Do the same in a vacuum and both would fall at the same rate.
When a car moves, the air resistance and drag forces it experiences are much more severe than anything we could feel. We move too slowly in comparison to a car, and thus cannot feel much at all. When a car moves however, it is hitting quadrillions of air molecules at extreme speeds. This alone would have been enough to slow down a car by a lot, but there’s more yet.
These molecules compress when the front end of the car moves closer to them. What this means is that the air pressure directly in front of the car is much higher than the air pressure in the space around it. Because of this, the air molecules then rush to the sides, underside, and top of the car to fill in the lower pressure area. When this happens the car experiences even further resistance as the molecules collide all across its body on their way to its sides.
But then another factor comes into play. The area immediately behind the rear end of the car is continually creating a vacuum. This is because when the car moves incredibly quickly, the space left behind it is suddenly empty. The air molecules rush in to fill the vacuum, but there is always this minuscule time frame where there is indeed a vacuum. And as vacuums tend to do, this vacuum tries to pull in every thing around it, including the car. Adding in yet another reason the car doesn’t go as fast as its engine’s energy output dictates that it should.
How Cars Use Aerodynamics to Combat These Shortcomings
So, now we finally get to how cars apply aerodynamics to beat all these odds and deliver a somewhat efficient performance relative to power consumed. Simple; car chassis try to minimize all these types of air resistance and drag forces as much as they can by being designed such that they reduce their production in the first place.
For example, cars with a narrower front hood or grill experience less frontal pressure. Less frontal pressure means less compressed air. And less compressed air means less air molecules rushing to the sides to fill in higher pressure areas. The sides and top of the car are also designed so that the flow of these molecules can be as non-intrusive to the car as possible. Usually this type of chassis smoothly converges on a very streamlined tail, ensuring that air molecules fill in the vacuum left behind in the car’s wake as soon as they can.
Car’s also try to keep as small of a space as possible beneath their chassis. The smaller the space between the underbelly of a car and the road, the less the air molecules can rush through there. Windshields are also made as slanted as possible along with the sloping chassis to reduce direct air collision and resistance. You will notice how racecars follow all these guidelines during their construction. In addition to all this however, racecars also use wings and spoilers to create downforce, a downward force produced thanks to aerodynamics that pushes the car further in the ground so that its tires can better grip the track’s surface for sharper and more accurate turning.
And that is how the science of aerodynamics helps us understand the limitations our cars face and overcome them by simple measures during chassis design. If you understood the forces explained above perfectly, you will realize that the perfect shape for a chassis to encounter as minimal air resistance as possible is the shape of a teardrop. Cars cannot be designed like that at this point in time due to their closeness to the ground. However, airplanes are already designed like this, and we presume that if flying cars really do exist in the future, they are probably shaped like teardrops as well.
For more interesting articles on automotive technology, check out our collection featuring posts like our discussion on whether autonomous driving can overtake physical driving or how automatic braking technology works. For fun articles about historical events, we recommend starting with our historical account of the modern rivalry between Lamborghini and Ferrari or our list of the most expensive luxury cars of the 1980’s.