Vortex ring toys
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A vortex ring toy generates vortex rings — rolling donut-shapes of fluid — which move through the fluid (most often air, and sometimes water). A smoke ring is a common example of a vortex ring. Because of the way they rotate, a vortex ring can hold itself together and travel for quite a distance.
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[edit] Vortex ring toys
The most common vortex toy works by expelling a quantity of air from the toy in such a way as to create a vortex ring. The energy from this vortex is transferred between air particles, in effect moving the vortex downrange. The core region of the vortex ring always consists of the same fluid, as it travels through the fluid. While outside this core the fluid will be set in motion by the approaching vortex ring, move for some time and return to rest after the passage of the ring. That is way for instance a smoke ring stays visible after quite long distances of travel; while most of the smoke from outside the vortex ring core is left behind in the region where the vortex ring sourced from.[1]
Single vortex rings are remarkably stable in diameter and speed, and can travel in quiescent air over long distances before their kinetic energy is dissipated by fluid friction. Outside its core, energy is transferred from one fluid parcel to the next, while the parcels just outside the core have nearly the same velocity as the parcels just inside, so also without much friction (since friction originates from difference in fluid velocity between adjacent fluid parcels).
Upon striking an object, the ring proceeds to pummel the target with a short, brief burst of swirling wind as the vortex dissipates. An interesting demonstration of the airflow pattern of a vortex ring toy can be made by having a smoker blow a smoke cloud into the toy prior to it being fired. The smoke will travel in the vortex, making a very large smoke ring. Some toys are built with a smoke generator in the toy, with the purpose being to blow smoke rings.
[edit] See also
[edit] Notes
- ^ Batchelor, G.K. (1967), An introduction to fluid dynamics, Cambridge University Press, ISBN 0-521-09817-3, pp. 521–526. }}
[edit] External links
- Fluid dynamics lecture covering vortices
- An animation of a vortex ring
- Giant vortex ring generator
- Professor T.T. Lim's personal site at University of Singapore. Includes rings collisions and a number still images, amongst other things.
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