How Air and other Gases Move - Aerodynamics

Aerodynamics is the study of forces acting on an object. These forces become active when an object moves through the air (or gases). It is important to understand these forces for the design of airplanes, sailboats, cars, and other objects moving quickly through the air. Buildings, bridges, and windmills are also affected by wind moving past them.

Most of the sections in this chapter are about the motions of air around objects, rather than other gases. When the motions and shape of an object are understood the aerodynamic forces can be figured. The flight possibilities of the object can, then, be discussed.

How High Speed Gases Change - Gas Dynamics

When air flows over an object at very high speeds, like over fighter aircraft, or goes through jet engines with very high temparatures, the normal rules of aerodynamics sometimes don't apply. For these special cases another area of study, gas dynamics, has been developed. Gas dynamics expands the rules and laws of aerodynamics to include high speed flows and high temperature flows.

Sometimes, if an aircraft flies so high up and so fast, even the rules of gas dynamics break down. At high altitudes the air molecules are very far apart. Also, the temperatures around the plane can be so high that they cause chemical reactions among the air molecules. This is often called the hypersonic region. Hypersonics is the study of the air motion in these conditions. The government is currently building a High Speed Civil Transport (HSCT) that would fly in this region!

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Last modified: Mon Jun 15 20:45:02 PDT 1998

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