How do airplanes actually fly? - Raymond Adkins

Summary

Albert Einstein, renowned for his theory of relativity, made a flawed attempt at designing an airplane wing in 1917 based on incomplete flight theory. The video explains how planes generate lift, debunking the common 'longer path' explanation of air flow over curved wings. Instead, lift results from a pressure difference created by the wing's motion through air, which accelerates the air above the wing, lowering pressure and generating upward force. While Einstein's design failed due to excessive wing curvature, modern engineers use complex equations to model air flow, offering a deeper understanding of lift in flight.

Takeaways

• 😀 Einstein's 1917 airplane wing design was flawed due to incomplete flight theory.
• 😀 The 'Longer Path' or 'Equal Transit Time' theory of lift has been debunked as incorrect.
• 😀 Lift is generated by pressure differences between the top and bottom surfaces of the wing, not by air molecules meeting at the same time.
• 😀 Air behaves like a fluid, and objects lighter than air are buoyant while heavier objects require lift to stay aloft.
• 😀 A wing's curvature affects airflow, but too much curvature can lead to turbulent air and loss of lift.
• 😀 The real cause of lift comes from the faster-moving air above the wing and the lower pressure created as a result.
• 😀 Centripetal acceleration causes air above the wing to speed up, contributing to the pressure difference that generates lift.
• 😀 A flat wing that is tilted upwards can still generate lift if the air bends around it correctly.
• 😀 The Navier-Stokes equations are used to model air’s flow around a wing and accurately predict how lift is generated.
• 😀 Modern aerodynamics views lift as a fluid dynamic process, not as a simple force or a mystery.

Q & A

What was Albert Einstein's contribution to aeronautics in 1917?

In 1917, Albert Einstein designed an airplane wing based on an incomplete theory of flight. His design was flawed due to a misunderstanding of how lift is generated, particularly regarding the curvature of the wing.

What is the commonly misunderstood explanation for how airplanes generate lift?

The 'Longer Path' or 'Equal Transit Time' explanation suggests that air molecules travel faster over the top of a curved wing, creating a pressure difference that generates lift. This explanation has been thoroughly debunked.

Why is the 'Equal Transit Time' explanation incorrect?

The 'Equal Transit Time' explanation is incorrect because air molecules above and below the wing do not need to meet at the same time. Air flowing above the wing actually reaches the trailing edge faster than air below.

How does lift actually work in terms of airflow around a wing?

Lift is generated by a pressure difference between the upper and lower surfaces of the wing. As the wing moves through the air, the airflow above the wing speeds up, reducing pressure, while the airflow below moves slower, creating higher pressure. This pressure difference results in the upward force of lift.

What role does the wing's curvature play in generating lift?

While the curvature of a wing affects how air flows around it, it is not the sole cause of lift. A flat wing tilted upwards can also generate lift, as long as the airflow around it creates a pressure difference between the upper and lower surfaces.

What can happen if a wing is too curved or steeply angled?

If a wing is too curved or steeply angled, the airflow above the wing may detach, causing turbulence. This can lead to a loss of lift and instability, which is likely what happened with Einstein's wing design, nicknamed 'the cat’s back.'

What additional factors influence the generation of lift beyond the basic pressure difference?

Other factors such as the airflow meters beyond the wing’s surface, air vortices formed at the wing’s tips, and the deflection of air contribute to the generation of lift. These elements add complexity to the process of flight.

How do engineers accurately model airflow around a wing?

Engineers use the Navier-Stokes equations to precisely model air's flow around a wing. These mathematical formulas help predict how lift is generated by detailing the changes in pressure and velocity as the air interacts with the wing.

What did Einstein believe about the wing's curvature that led to his flawed design?

Einstein believed that increasing the curvature of the wing would generate more lift. However, this resulted in instability and poor performance, as excessive curvature caused the airflow to become turbulent, disrupting the wing's ability to generate lift.

What does the video suggest about the complexity of the concept of lift?

The video suggests that while the basic idea of lift is straightforward, it remains a complex and nuanced concept. Factors such as the specific airflow dynamics and the intricate mathematical models used by engineers all contribute to the complexity of understanding how lift works.