flightphysics

flightphysics - How birds fly Bernoullis Law Static...

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How birds fly

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Bernoulli’s Law Static Pressure + Dynamic Pressure = a constant Static Pressure is air pressure exerted by still air uniformly on an object -- barometric pressure. (example: a balloon at low and high altitudes) Dynamic Pressure is pressure exerted by moving air on an object. (example: wind on your face) Dynamic pressure is proportional to (velocity) 2
Demonstrations Venturi Tube The ball in the funnel – how it’s explained Blowing on the upper surface of a piece of paper Why houses “explode” near tornados and roofs blow off in hurricanes Cross section of an airfoil, and how lift is generated.

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How can a bird increase lift? There are basically two options: 1) Increase speed of wing relative to air . This is highly effective. But, it’s a “two-edged sword” – slow flight is very difficult. 2) Increase angle of attack . Air over top of wing has to travel faster Lift increases proportional to angle up to 15-20 o >15-20 o results in loss of laminar flow These two strategies are often combined (lots of combinations, each appropriate for different circumstances)
Slow speed flight is hard! A trick. . A second air foil on top of first channels air over top of wing to maintain laminar flow. In birds = the alula

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Planes use the same trick (Slats) Note: slow flight & high angle of attack + fixed slat Slats and flaps are often employed at the same time
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This document was uploaded on 08/24/2011.

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flightphysics - How birds fly Bernoullis Law Static...

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