In a table fan, the blades move around in circular way and we feel air/wind when sitting on front of it. How does this happen?
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2 Answers
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The blades are at an angle. As the blade moves down it hits an air molecule and the air molecule "bounces off" toward you.
It's just like hitting a ball in tennis/baseball
answered Oct 19, 2011 at 21:36
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1$\begingroup$ This suggests a violation of no-slip at the fan edge. It is better to state it in term of air-currents reflecting, rather than atoms, because the atoms are not moving individually. $\endgroup$ Commented Oct 20, 2011 at 6:05
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$\begingroup$ If atoms don't move how does a fan distribute a smell accross the room? $\endgroup$ Commented Oct 20, 2011 at 13:00
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1$\begingroup$ The atoms which are directly in contact with the fan don't move. The atoms which "bounce off" the fan are bouncing off the layer of air stuck to the fan. This is the continuum approximation and it is valid unless you have a shock-wave super-fan. See also this: physics.stackexchange.com/questions/1343/… $\endgroup$ Commented Oct 21, 2011 at 2:11
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Due to the rotational motion of the blades a pressure variation is created and the air blows.
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2$\begingroup$ Hello and Welcome to Stack Exchange. As it stand, your answer has very little value, since it doesn't explain anything. How is the pressure variation created? What is the precise idea? Please include more information! $\endgroup$– MartinCommented Dec 7, 2015 at 9:45