| Aerodynamics is a branch of fluid mechanics that deals with the motion of air and other gaseous fluids, and with the forces acting on objects in motion relative to such fluids |
Bernoulli's Principle Bernoulli's principle, a fundamental law of fluids in motion, states that when flow speed increases, pressure decreases and vice versa. An airplane wing is designed so that air will flow more rapidly over the upper surface than the lower one, decreasing the pressure on the top surface and increasing the pressure on the bottom surface. This difference in pressure provides the lift that keeps the airplane in flight. |
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| Drag is a force that acts against objects moving through air. The jet engine or the propellers of an airplane must provide enough thrust force to overcome drag. Streamlining the airplane body significantly reduces drag forces. | |
| Supersonics Supersonics is the branch of aerodynamics that concerns phenomena arising when the speed of an object exceeds the speed of sound. The speed of sound is represented by a so-called Mach number Ernst Mach, which is the speed of the object divided by the speed of sound in the same substance under the same conditions. Mach numbers represent actual flight conditions more accurately than distance per hour. |
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Photographic studies of artillery projectiles in flight show the atmospheric disturbances encountered in supersonic flight. At subsonic speeds, the only atmospheric disturbance is turbulence in the projectile's wake. As the speed passes M-1 (Mach number 1), shock waves arise from the nose and tail and spread from the projectile in a cone. |
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| This research has led designers to make
modern high speed airplanes with wings that are swept
back to avoid the shock wave from the nose of the plane.
Research has identified other factors, such as the shape
of the projectile, the rate of gas flow, and atmospheric
pressure, that influence the efficiency of the
projectile's flight. Aircraft designers have also used
wind tunnels to test airplane models and airplane parts
in air currents at supersonic speeds. |
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Drag and Aerodynamics The shape of an object drastically affects the degree to which air resistance, or drag, impedes the object's motion. For example, a sphere, top, and especially a square, bottom, both force the air to redirect itself, slowing the objects down. An airfoil, middle, minimally disturbs the air as it travels, so the airfoil experiences little drag. |
| Thinkquest Team 18033 |
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