Science of Flight Essentials of Aerodynamics

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Airfoils and Wind Tunnels

Aerodynamics is the way objects move through air. Whether the object is a large airliner, a model rocket, a beach ball or a kite—its aerodynamic characteristics affect its motion. The word Aerodynamics comes from two greek words: aerios, which means air, and dynamis, which means force. So, an object needs a force to lift it. One object that creates this lifting force in an airfoil. An airfoil is a structure—such as a wing or propeller blade—that when exposed to a flow of air generates a force.

It’s important to know an airfoil’s parts because their relationship to each other affects the way an aircraft flies. The force an airfoil exerts can be either a lifting force, as in the case of a wing, or a force that pushes or pulls the object—as in a propeller blade. It can also be a combination of the two—as in a helicopter propeller—that both lifts and pulls.

When all these elements of an airfoil come together in just the right way, the airfoil will produce a lifting force when it’s propelled through the air.

How do we know if an airfoil will work?

Aircraft designers use wind tunnels to test models of new aircraft. Wind tunnels are controlled spaces for testing airflow over a wing,
aircraft, or other object. In a wind tunnel, a researcher can carefully control the airflow conditions, which affect the forces on an aircraft. By carefully measuring these forces on the model, the researcher can predict how these forces will affect the full-size aircraft.

Watch

Watch the following video showing how a wind tunnel works. Observe how the airflow changes when the airfoil is rotated up or down (referred to as the angle of attack).

NACA 25112 AIRFOIL, WIND TUNNEL TESTING