November 8, 2024

Bowen Zhou 

12th Grade

St. Francis Preparatory High School

When you see a bird, it flaps its wings to create a lift to fly. Similarly, the wings of an aircraft create lift with its wings. But instead of flapping like a bird to fly it mainly uses the pressure difference to create lift. Some people say it comes from Bernoulli’s Principle, or Newton’s Third Law, while others don't. It does this with things like the angle of attack and the shape of the wing. 

But what exactly is lift? A lift is a mechanical force caused by a solid object interacting with a fluid, like water or air. We can use “lift” in a large variety of ways. Despite being called lift, it can be used for things besides “lifting”, for example, it is used in the spoiler in a car to generate downforce to keep the car on the ground, or the propeller of a boat to propel itself. But in the case of aircraft, it is used to fly. 

Using Bernoulli’s Principle, lift is created because air moves faster over the top and slower over the bottom. Bernoulli’s Principle says that a fluid with a higher velocity has a lower static pressure, using this knowledge, the air below the airfoil has a higher pressure because it is slower, and the air above has a lower pressure because it is faster. This creates a pressure difference and a net upward force, creating lift. A common misconception is that since the top is curved, the air goes along a longer path, and to reach the end of the airfoil at the same time as the bottom, it has to go faster, which is incorrect. This is an old way of thinking; early airfoils were curved, but modern airfoils could even be symmetrical and still produce lift, like in the case of helicopters. You can also use Newton’s Third Law of Motion to describe lift. When the airfoil deflects the air downward, the air creates an opposite reaction, which pushes the airfoil up. Neither of these is wrong, but rather, they work in tandem with each other. Neither Bernoulli nor Newton tried to explain the aerodynamic lift of an object.

Another important factor to lift is the Coanda Effect. This affects lift because the Coanda effect keeps the air attached to the wing for it to keep creating lift. Lift is also created from the angle of attack. The angle of attack is the angle of the chord of the wing, or the line that goes from the leading edge and trailing edge, relative to the wind. The greater the angle of attack, the greater the lift, this is because it increases that pressure difference over the wing. But this is only up until a certain point. When it reaches its critical angle of attack, the lift is significantly reduced because of airflow separation. 

People are still figuring out how lift is created. Many theories have come about like Bernoulli’s Principle and Newton’s third law of motion, and even some incorrect theories, but we have yet to find a universal “truth” or explanation for lift. But they all work together to come up with some semblance of how lift is created. Even if we don’t know exactly how lift is created, engineers still optimize and make ever more efficient wings to make flights more efficient.