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There is a YouTube video that visualizes the air flow around a propeller for various configurations. I caught a screen shot of a moment that more or less shows what is going on: As you can see, this happens at 2:07 into the clip - this happens to be for a dual rotor configuration (two counter rotating blades) but the principle is the same. Behind the ...


8

You don't have a fluorescent light but an LED light that time-multiplexes different colors to achieve white. The fan blades act as a stroboscope and make the switching frequency of these LEDs visible. Or... I am wrong! So back to the drawing board: I did the experiment. Most fluorescent lights in my house do not show this effect, at all, but one does, ...


6

Here's a standard fan with some (hard to see) arrows indicating air flow. The fan works by pulling air in and then making it move faster. The air flow behind the fan is slow moving and wide (you can see the arrows behind the fan coming from above and below the fan blades) whereas the air flow in front of the fan is fast moving and narrow (which follows ...


4

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 ...


2

Intuitively, it seems entirely possible. The "shape" of the air current blown out by both fans looks like a hollow cylinder, since the air is blown at high velocity near the ends of the blades, and lower velocity towards the center. If you put two of these fans facing each other, the two "cylinders" of air current will collide with each other and create a ...


2

Think about the air around the fan at any given time: The amount of air flowing into the fan must equate to the air flowing out of the fan. The amount of air that passes through an area in a given time is related to the velocity of the air i.e. the faster the air is moving, the more air that can flow through a fixed area/hole/slot. The fan blades apply a ...


2

Simply put, it's because a fan imparts momentum on the air (i.e. accelerates it), so in front of the fan you get a roughly conical jet of high speed air. At the back side of the fan there is a low-pressure region which makes the surrounding air move towards the fan (following the pressure gradient) from a large solid angle, as you already stated. This is ...


2

This is really a comment, but it got a bit too long for the comment box. The term efficiency has a very specific meaning in Physics. In the case of a fan we can measure the power the fan consumes simply by measuring what current it draws from the main. We can in principle measure the power the fan produces by measuring the velocity of the air stream ...


2

Unlike John Rennie, I think that the problem is not in the efficiency of this system but in the fact, that it will not generate considerable lift. So even if marketing materials are completely true and Dyson Air Multiplier is more energy efficient than conventional fans this efficiency only applies to moving air (which is its intended use) but not to the ...


1

My previous answer was based on physical principles. This answer is based on biological principles. I noticed in the question @JoeBlack stated "I feel air" meaning you are using your own biology to sense the air flow. Air flow can be felt by pressure of turbulence on the skin. It can also be felt by perceived temperature. Usually a person turns on a fan ...


1

The fans work by entrainment of surrounding air by the jet blowing out of a slit in the ring. Obviously it is optimized for entraining air from behind the ring, but it should also pull in air from the sides if the back is blocked. Most fluid dynamics textbooks will discuss the problem of a planar jet coming out of a wall, this is essentially the same ...


1

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 ...



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