Disks and disk-like objects (frisbees, pie pans, round cardboard piece, hats of all sorts, and many other things) can fly well when thrown along with a spinning force which creates a gyroscopic effect stabilising the object. What causes disk objects to be able to generate lift?
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asked Apr 9, 2016 at 18:13
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$\begingroup$ Just the angle of attack. The stability comes from the rotation. $\endgroup$– ratchet freakCommented Apr 9, 2016 at 18:15
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3$\begingroup$ Possible duplicate of How do wings generate lift? $\endgroup$– SimonCommented Apr 9, 2016 at 18:49
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$\begingroup$ This one should address the topic nicely. A disc has a variable leading edge sweep over span, but works otherwise like a paper airplane. Rotation makes sure that the pitch angle will not change. $\endgroup$– Peter KämpfCommented Apr 9, 2016 at 21:07
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$\begingroup$ One way to view this is that the Frisbie creates drag as is descends. Thus it acts like a parachute. $\endgroup$– user3344003Commented Apr 9, 2016 at 21:16
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4$\begingroup$ Why to close this? It is clearly about the list generated by the disk-like flying object and not the paper plane. If this is the same, should be explained. A plane spinning like a thrown disk is unlikely to fly well. $\endgroup$– h22Commented Apr 11, 2016 at 8:13
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1 Answer
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As with regular wings, the angle of attack and the dynamic pressure determine the lift of a frisbee.
This short paper by V. Morrison gives a short overview. If you want to dig deeper, Sarah Hummel and Eugene Motoyama (sorry, paywalled) have done more detailed work on flying discs. The following pictures were shamelessly copied from the work of Kevin Walsh. They show that the rounded edge improves airflow over the disc by delaying flow separation.
Flow around a frisbee (source)
The frisbee can be seen as a wing with an airfoil that looks the same from both directions. This incurs a small separation area at the rear end, but prevents much larger separation at the leading edge at medium angles of attack. Morrison found the farthest flying distances with an angle of attack of 12° and a starting speed of 14 m/s.
Since the center of pressure is close to the leading edge, a disc would quickly topple over due to the different locations of the center of pressure and the center of gravity. By spinning, it can be stabilized:
Difference between spinning and non-spinning frisbee (source). Inertia / gyro forces prevents the spinning frisbee from pitching up.
answered Apr 10, 2016 at 8:01