it’s really been getting on my nerves the amount of times i have to clean this thing, how do they stick and accumulate on a fast moving blade? i’d greatly appreciate a response!
In: Technology
Remember rubbing a balloon up against your hair as a kid and your hair would stick to the balloon? Your fan is the balloon and dust is the hair. As the fan spins, dust is attracted to the fan like hair on a balloon and sticks to it.
Dust seems to be dry, but it is often greasy. Your danders e.g. contains your body fat. That is sticky. Another effect is that dust is a bit like velcro and the particles hook together and as u/Target880 mentioned is the static electricity. This all together makes a mess.
Hey, aerospace engineer here. There’s a long complicated aerodynamic explanation but here’s the short of it.
ELI5: at the point where air meets the surface of the blade, the speed of the air is zero. Therefore, a piece of dust on the surface is not being blown anywhere. When you spin the blade through the air, it slams dust particles onto the blade, and those particles don’t get blown anywhere.
This is similar to why water accumulates on a windshield even though you’re travelling at 60 mph.
Edit: after talking it through with another reddit, I was off a bit. The airspeed is zero, but the horizontal forces is not. The likely cause for sticking is that the dust particles are not large enough for the air pressure to blow the dust off the fan. Perhaps there is an upper limit to the amount of dust that can accumulate, at which point the surface area is big enough for the forces to blow it off.
The blade that moves through the air tends to get an electrostatic charge and if can result in the dust getting attached to the blades a lot more than if there was no charge. The dust that accumulates tends to be very fine particles.
Because the blades push the air around a lot of air will pass over the blades so the can accumulate dust faster rotation then stations for the simple reason there is more air and dust in contact with them when they rotate.
The moment of air can remove stuff but stuff can still be stuck to a surface. There is a reason you need to clean cars even if they move fast through the air.
Passenger jets tend to have windscreen wipers on the two forward-looking windows so you can remove water or anything ells that accumulate on them. If you fly through an insect swarm the will accumulate on the windows and another part of the aircraft.
It is basically sucking air in from one side and this sucks dust with it.
While you’d think that this would mean the dust is on the “back” of the fan blades, it is mostly on the front because they are designed to “hit” the air that comes in out toward the front.
Not all the dust sticks to them though and they push a lot of it through. Hence, you see that dust accumulates inside of a desktop pc case fairly quickly despite being a mostly closed off container.
TL;DR:
sucks in a lot of air which has some dust in it and the blades hit the dust causing the dust to stick to them.
Wow!, I just wiped down my lounge blades last week or the week before and wondered the same. I also see the bedroom blades are clean so why is the lounge one dusty?
Static electricity happens when the fan blades travel through the air quickly and brush the air molecules to move them out of the way. These molecules will build up an electrical charge on the leading edge of your fan blade, which is why dust particles will collect and stick more to one side than the other.
Because I was lazy to formulate the principle, I just copy pasted above from google search result
The air touching the blades isn’t moving. Kinda hard to conceive but YouTube wind tunnel testing with cars, they use smoke to test the aerodynamics. If you watch closely the smoke never actually touches the car, but moves ever so slightly above it. That small cushion of air is how it’s able to stay and stick
Oil, water, or static electricity (especially for plastic desk fans) can all help dust stick to a surface. For kitchen fans, oil is usually the culprit (and it can be bright orange if you cook with chili pepper).
You also have to remember the fan is not always running so that will give dust a time to build and attach
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