The Three Basic Forces: The Basic Principles Of Aerodynamics

INTRODUCTION Aerodynamics is the study of how gases interact with moving bodies. Because the gas that we encounter most is air, aerodynamics is primarily concerned with the forces of drag and lift, which are caused by air passing over and around solid bodies. Engineers apply the principles of aerodynamics to the designs of many different things, including buildings, bridges and even soccer balls; however, of primary concern is the aerodynamics of aircraft and automobiles. THE BASIC FORCES OF THRUST,DRAG AND LIFT

There are three basic forces to be considered in aerodynamics: thrust, which moves an airplane forward; drag, which holds it back; and lift, which keeps it airborne. Lift is generally explained by three theories: Bernoulli 's principle, the Coanda effect, and Newton 's third law of motion.

Bernoulli 's principle states that the pressure of a moving gas decreases as its velocity

This is accomplished with a motor-driven propeller or a jet engine. When the airplane is in level flight at a constant speed, the force of the thrust is just enough to counteract the aerodynamic drag. Moving air can also generate forces in a different direction from the flow. The force that keeps an airplane from falling is called lift. Lift is generated by an aircraft wing. The path over a wing 's curved top is longer than the path along the flat bottom of the wing. This causes the air to move faster over the top than it does along the bottom. With all other factors being equal, faster moving air has lower pressure than slower moving air, according to Bernoulli 's principle. This difference is what allows the slower moving air to push up against the bottom of the wing with greater force than the faster moving air is pushing down against the top of the wing. In level flight, this upward force is just enough to counteract the downward force caused by