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NEWS: How Dyson's Air Multiplier works

Duncan Geere — Tue, 13 Oct 2009 13:45:08 +0100

A little bit of Fluid Dynamics for a Tuesday afternoon

So, you've read about the Dyson Air Multiplier, and you've looked at the photos, but you're still baffled about how the damn thing works. You've seen vague promises of "Engineering" being responsible (which we've come under criticism for, for some reason), but here's - in gory physics-y detail - roughly what's going on inside Dyson's mysterious new bladeless fan.

The Air Multiplier uses friction in the air to push out its cool breeze. Around the rim of the circular fan is a little opening from which jets a very thin (1mm or so) stream of air at 55 mph. That thin stream of air pulls more air into the stream thanks to the aforementioned friction - Physicists call this process entrainment.

At the same time, the air that gets pushed away from the ring towards your beautiful face creates an area of low pressure - not quite a vacuum, but the same effect - in the ring. That low pressure pulls in more air from behind the machine (filling the gap) which is then in turn drawn into the air stream. That's called inducement.

The engineering challenge, however, is in keeping that stream of air flowing smoothly - balancing how fast the air is travelling (its "inertia") with how thick it is (its "viscosity"). Physicists have an equation which represents this balance, and it results in something called the Reynolds number.

Some quick calculations (using 55mph air flow, a 1mm gap, 1.2 kg/m^3 air density and 18.27 * 10^-6 Pa s viscosity) show that the Air Multiplier has a Reynolds number of around 1615 - relatively low. That means that the air flow out is pretty smooth (or "laminar", as physicists call it) - something seen in this image of air speeds:

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If all those equations confused you massively, think of a garden hose. If you turn on the tap half way, then the flow out of the hose is smooth - it stays together in a stream when it exits the end of the pipe until it hits your flowerbed. But if you squeeze the hose, making the exit smaller, or if you turn the tap on full, then the water sprays all over the place - much less easy to control. That would have a high Reynolds number.

In a fan, you want a smooth airflow which stays aimed at whatever you point it at for upto 5 or more metres away without going all over the place, wasting energy in turbulence. The Air Multiplier appears to have achieved this with its low Reynolds number.

The "multiplier" part of the name refers to how much efficiency it saves. It sends approximately 15 times more air at you thanks to taking advantage of these physical processes than it actually has to drive through its own internal spinning turbine. Of course, regular fans gain some of these effects, too, though they're more likely to suffer inefficiencies due to turbulence caused by the speed of the blades and the "open" air around it. Dyson's turbine is enclosed in the body of the unit - the "handle" of the magnifying glass, if you will.

So there you go. Of course, we're tech fanatics, not professional physicists, so if we've got something slightly off in the explanation above, and you think you know better, then don't hesitate to drop us a comment below.

NEWS: PHOTOS: Dyson's Air Multiplier

Duncan Geere — Tue, 13 Oct 2009 12:47:16 +0100

Vacuum design meets the humble fan

Dyson has unveiled its "Air Multiplier" fan and Pocket-lint was on hand to get some snaps of the interesting magnifying-glass-shaped design. The company tried very hard to keep its bladeless fan a secret, but news leaked out some months ago so the eventual announcement was almost something of an anticlimax.

The fan does what it purports to do very well. It blows air at you, basically. It does this without blades thanks to a very thin stream of air which the fan emits from around the rim at 55mph. Without boring you with an extensive description of fluid dynamics, it works because of friction - if air is travelling in a jet, air alongside it tends to get pulled along too.

It can therefore shoot out a relatively thin stream of air, and that small quantity of air will pull upto 15 times more air along with it. Pretty efficient, compared to a traditional fan (though a similar principle does apply there, too). In terms of volume, the fan is about as noisy as a regular fan, if a smidge less.

What was most surprising about the Air Multiplier was the price - ?200 for both the 10-inch and 13-inch versions. It's pretty and all, but when a regular fan is a fiver, it seems tough to justify splashing out two hundred quid on a desk fan, however beautiful it is. What do you guys think?

Tags: Home And Kitchen Fans Dyson Photos Dyson Air Multiplier

PHOTOS: Dyson's Air Multiplier originally appeared on http://www.pocket-lint.com on Tue, 13 Oct 2009 12:47:16 +0100

NEWS: Dyson Air Multiplier fan goes bladeless to keep you cool

Stuart Miles — Tue, 13 Oct 2009 02:20:30 +0100

Winds of change from James Dyson

Dyson, as we reported they would some months ago, has today announced the launch of a bladeless fan that it hopes will revolutionise the fan market.
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Using technology from it's bagless vacuum cleaners the new bladeless fan will be silent, and look more like a giant ring as opposed to your average wind blower found around the world for under ?20.

However those hoping for a cheap price will be disappointed. Costing $300 for the 10-inch model and $330 for a 12-incher it won't be for those on a budget.

Available initially in America and Australia, the Dyson Air Multiplier fan uses engineering to "multiply" air 15 times and push out 119 gallons of smooth and uninterrupted air every second according to the company.

"We realised that this inducement, or amplification, effect could be further enhanced by passing airflow over a ramp", says Dyson. "And of course this was the point where the idea of a bladeless fan became a real possibility. Here was a way to create turbulent-free air and finally do away with blades", said James Dyson who became a technology tsar?for the Conservative party in the UK.?

According to the company "air is drawn into the base of the machine. The air is forced up into the loop amplifier and accelerated through the 1.3mm annular aperture, creating a jet of air that hugs the airfoil- shaped ramp. While exiting the loop amplifier, the jet pulls air from behind the fan into the airflow (inducement). At the same time, the surrounding air from the front and sides of the machine are forced into the air stream (entrainment), amplifying it 15 times. The result is a constant uninterrupted flow of cooling air".

The fan will come in three versions and two sizes; a 10- an 12-inch option and two different colour schemes.

It is currently only available at Dyson.com and the Conran shops.