- Vortex ring toys
vortex ringis a rolling donut of fluid which is moving through another fluid. A smoke ringis 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.
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, but without forcing the air that was initially displaced through the atmosphere ("citation needed")(this condition would greatly reduce the toy's effectiveness.)
(This disagrees with classical fluid dynamics [Classical Fluid Dynamics] --and common sense. If it were true, the smoke in a ring would be traveling, leaving the air behind, additionally, since a vortex can be generated using a different fluid than the surrounding, and that chemically different fluid will hit the target, it must be assumed that the vortex ring carries at least a major portion of the ejected fluid. According to classical fluid dynamics, the rotation of the air within the vortex--from the inside to the front to the outside to the inside, creates a dynamic flow on the outside of the ring which will greatly reduce the friction of passage through the medium.)
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, such as the Zero Blaster, are built with a smoke generator in the toy, with the purpose being to blow smoke rings.You may use dry ice or steam as appropriate.
Vortex ring generators you can make
* Hit the bottom of an empty plastic milk/juice jug
You can make a vortex ring generator by:
* cutting a round hole in the base of a bucket
* placing film over the top of the bucket (like a drum).
You can then make a vortex ring by holding the bucket and hitting the drum. You can use this vortex ring generator to blow out a candle up to 6 or 7 metres away.
1 [http://maxwell.ucdavis.edu/~cole/phy9b/notes/fluids_ch3.pdf classical fluid dynamics lecture covering vortices]
* [http://www.amasci.com/wing/smring.html good animation of a vortex ring]
* [http://cas.umkc.edu/physics/sps/projects/vortex/vortex.html Giant vortex ring generator ]
* [http://serve.me.nus.edu.sg/limtt/ professor T.T. Lim's site at the University of Singapore. His video gallery includes, among others, rings colliding head on and at an angle and a number still images.]
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