I'm curious as to how the Dyson air multiplier fan works. So far I understand that it creates negative air pressure that causes air behind and around the device to be sucked into the air stream and blown out. My question is how is the negative air pressure created? I haven't found an explanation for that yet.
There seems to be a lot of B.S. in the ads for this product, making it seem much more complicated than it really is.
It seems that the fan contains an ordinary fan in its base, and squirts out high speed jets of air from around the big ring. These jets of air push on the ambient air. This slows down the individual jets but pushes along a greater volume of air.
This link seems to have a more reasonable explanation than many other sites, which tend to simply reproduce press-release hyperbole: http://www.pocket-lint.com/news/27887/how-dysons-air-multiplier-works
For your first question, think of the air kind of like sand. If you just slide you hand across the surface, some grains beneath the surface will move due to friction between the sand grains transferring the energy of your hand to other sand grains. The same thing happens in the air inside the ring, as air shoots out of the slit surrounding the ring it collides with the air particles already inside the ring and transfers some energy to them, thus pushing them out of the front of the fan.
Second, the low pressure area. As the air inside the ring is getting pushed out of the center of the ring by the air blowing out of the slit, then there will be a void, for lack of a better term, in the center of the ring. Think of this void as the low pressure zone, as the void grows in size, the air at the back of the fan wants to flow into the void and there fore gains momentum towards the front of the fan and it gets accelerated from the friction as it flows past the slit in the ring.
air moving along the inner surface of the fan naturally creates a lower pressure inside... bernoulli's principle.