Greetings! The semester is over now, and we are back. Many thanks to all you loyal readers and casual readers out there, and your patience during our recent “down time.”

We now return to the feature presentation…

It turns out that aircraft wings are specially designed to provide an upward lift force when the aircraft is moving through air. They are designed so that the airflow over the top of the wing is faster relative to the airflow under the bottom of the wing. In fancier terminology, a streamline (line that is everywhere tangent to the airflow velocity) that is right above the top of the wing has a higher velocity than a streamline just below the bottom of the wing. This is achieved by making the top of the aircraft wing slightly more curved than the bottom.

Bernoulli's Equation

Bernoulli’s Principle relates velocity, elevation, and pressure of a streamline of fluid flow. For an aircraft, the fluid is air, because the wing moves through air. Essentially, the total quantity of velocity, elevation, and pressure must be constant for a streamline. From Bernoulli’s Principle, if the velocity is high, then the pressure is low, and vice versa. Therefore, for an aircraft wing, since the airflow over the top is faster than the airflow below, the pressure is lower at the top of the wing than at the bottom of the wing (it can be assumed that the elevation of the top and bottom of the wing are the same). It is this difference in pressure that leads to an upward lift force on the wing, which helps keep the aircraft elevated in the air during travel.

Schematic of Aircraft Wing

The specific shape of an aircraft wing is also meaningful to the operation of an aircraft, but that’s a topic that deals with advanced fluid mechanics. Perhaps a future post can explain the phenomenon.

Categories: Design, Science
Tags: Aircraft, Fluids, Lift
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