शैडोइंग अभ्यास: How do airplanes actually fly? - Raymond Adkins - YouTube के साथ अंग्रेजी बोलना सीखें

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By 1917, Albert Einstein had explained the relationship between space and time.

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By 1917, Albert Einstein had explained the relationship between space and time.

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But, that year, he designed a flawed airplane wing.

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His attempt was based on an incomplete theory of flight.

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Indeed, insufficient and inaccurate explanations still circulate today.

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So, where did Einstein go wrong?

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And how do planes fly?

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Though we don’t always think of it this way, air is a fluid medium— it’s just less dense than liquids like water.

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Things that are lighter than air are buoyant within it, while heavier objects require an upward force, called lift, to stay aloft.

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For planes, this force is mostly generated by the wings.

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One especially pervasive false description of lift is the “Longer Path” or “Equal Transit Time” explanation.

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It states that air molecules traveling over the top of a curved wing cover a longer distance than those traveling underneath.

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For the air molecules above to reach the wing’s trailing edge in the same instance as those that split off and went below, air must travel faster above, creating a pocket of lower pressure that lifts the plane.

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This explanation has been thoroughly debunked.

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Air molecules floating above and below the wing don't need to meet back up.

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In reality, the air traveling above reaches the wing’s trailing edge much faster than the air beneath.

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To get a sense of how lift is actually generated, let's simulate an airplane wing in motion.

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As it moves forward, the wing affects the movement of the air around it.

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As air meets the wing’s solid surface, a thin layer sticks to the wing.

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This layer pulls the surrounding air with it.

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The air splits into pathways above and below the wing, following the wing’s contour.

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As the air that’s routed above makes its way around the nose of the wing, it experiences centripetal acceleration, the force you also feel in a sharply turning car.

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The air above therefore gathers more speed than the air traveling below.

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This increased speed is coupled with a decrease in pressure above the wing, which pulls even more air across the wing’s upper surface.

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The air flowing across the lower surface, meanwhile, experiences less of a change in direction and speed.

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The pressure across the wing’s lower surface is thus higher than that above the upper surface.

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This pressure difference results in the upwards force of lift.

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The faster the plane travels, the greater the pressure difference, and the greater that force.

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Once it overcomes the downward force of gravity, the plane takes off.

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Air flows smoothly around curved wings.

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But a wing’s curvature is not the cause of lift.

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In fact, a flat wing that’s tilted upwards can also create lift— as long as the air bends around it, contributing to and reinforcing the pressure difference.

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Meanwhile, having a wing that’s too curved or steeply angled can be disastrous:

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the airflow above may detach from the wing and become turbulent.

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This is probably what happened with Einstein’s wing design, nicknamed “the cat’s back.” By increasing the wing’s curvature, Einstein thought it would generate more lift.

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But one test pilot reported that the plane wobbled like “a pregnant duck” in flight.

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Our explanation is still a simplified description of this nuanced, complex process.

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Other factors, like the air that’s flowing meters beyond the wing’s surface— being swept up, then down— as well as air vortices formed at the wing’s tips, all influence lift.

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And, while experts agree that the pressure difference generates lift, their explanations for how can vary.

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Some might emphasize the air’s behavior at the wing’s surface, others the upward force created as the air is deflected downwards.

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However, there's no controversy when it comes to the math.

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Engineers use a set of formulas called the Navier-Stokes equations to precisely model air’s flow around a wing and detail how lift is generated.

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More than a century after Einstein’s foray into aeronautics, lift retains its reputation as a confounding concept.

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But when it feels like it’s all going to come crashing down, remember:

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it’s just the physics of fluid in motion.

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With over 590 hotels and resorts across the globe, Marriott Hotels celebrates the curiosity that propels us to travel.

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शैडोइंग मोड सेट करें:
- प्रतीक्षा मोड: +3s या +5s चुनें — प्रत्येक वाक्य के बाद वीडियो स्वचालित रूप से रुकता है ताकि आप दोहरा सकें।
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शैडोइंग अभ्यास: How do airplanes actually fly? - Raymond Adkins - YouTube के साथ अंग्रेजी बोलना सीखें

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