Have you noticed that, for the most part, all commercial aircraft have a very similar shape? Despite design differences, the curvature and especially the wings, (which we will talk about in this article) tend to resemble each other. This is directly related to aerodynamics. Aerodynamics is the science derived from fluid mechanics that studies the reactions of air with objects moving around in it. How do aerodynamics interact with aircraft? Which parts of an aircraft are the most studied in this branch of science? And what’s taken into account when designing each part?
Aircraft Aerofoils
An aerofoil is an object or structure made to move through a fluid while creating dynamic forces and reacting to them. The effect of wind is considered when designing trains, ships, cars, and even buildings. But since here we are talking about aircraft aerodynamics, we can define aerofoils as curved structures that, as they move through the air, manipulate airflow to produce lift.
In other words, the aerofoils allow aircraft to stay in the air and move through it. We have already discussed the physical principles that define lift (Bernoulli’s principle and the Venturi effect).
Which parts of the aircraft do aerodynamics focus on the most?
Aeronautical engineers, who are responsible for aircraft design, apply the principles of aerodynamics to many parts of the aircraft, such as turbine blades, compressors, propellers, and so on. There are so many components to be considered in a project of this kind. But the main focus of aircraft aerodynamics is on the wings.
Key Aerofoil Elements
We know that the aim of aircraft aerodynamics is to generate lift. Now, let’s look at the parts of an aerofoil to understand the reason for its design. Consider the wing of an aeroplane:
- Upper surface. It is the top part of the wing, usually more curved than the lower surface.
- Lower surface. It is the bottom part of the wing, usually flatter than the top.
- Leading edge. This is the front part of the wing, where the airflow hits.
- Trailing edge. This is the rear part. At this point, the airflow leaves the wing.
- Aerodynamic chord. An imaginary line running from the leading edge to the trailing edge.
- Mean camber line This is also an imaginary line, which joins equidistant points between the upper and lower surfaces. To give you an idea, the mean camber line runs along the wing from the leading edge to the trailing edge, as does the aerodynamic chord. But in this case it is a curved line that will have the same distance along its entire length between the top and bottom.
Why Are Aerofoils Curved and not Straight?
Why is it that the external shape not only of aircraft, but of the vast majority of vehicles, is curved instead of straight? This is also explained by the Bernoulli principle. For example, the top surface of the wing is the most curved part and the underside is the least curved. The air flowing over the top surface will accelerate and, as explained by the Bernoulli principle, its pressure will decrease and generate a pressure difference between the top surface and the bottom surface. Such a design is essential to ensure that the forces acting on the aircraft (the wings in this case) cause the aircraft to operate as efficiently as possible.
Symmetrical or Asymmetrical?
Let’s go back to the wings. The upper and lower surfaces are not the same. However, there are cases where aerofoils can be symmetrical such as on supersonic aircraft. The main, and perhaps only, benefit of having the same top and bottom surfaces is that drag is reduced. But lift is also worse in this case. As a result, asymmetrical wing aerofoils are the norm for commercial aircraft.
Winglets are another key element in aircraft aerodynamics
Finally, in the basic wing aerofoil design, it is worth mentioning a relatively new element: winglets or wing tips. These elements also contribute to improved aerodynamic performance of aircraft.
Winglets are the tips of wing that point upwards. This element has been incorporated with two objectives in mind: to reduce the aerodynamic drag of the aircraft and to improve lift.