By that I mean literally sucking up stuff. The vent fan above my stove only seems to actually pull anything in while it’s on low; setting it to high makes it louder but stops pulling any smoke or steam up through the hood. I’m just curious how the hell that works; shouldn’t a faster spinning fan suck MORE? Is there some property of aerodynamics that was forgotten when they installed this shit?
Not exactly a scientist, and I agree with the other long answer about blades disrupting each other, so I’m replying to see if I can help you visualize/understand some of the forces at play.
My source is a Tom Clancy book about a sub war.
Typically the subs are stealthy, however if I remember correctly, I’d they decided to gun the engines (think something like 105% on the reactor), they could spin the blades really fast.
But compressing the water as the blade spins makes some of it high pressure and the other side of the blade low pressure.
This would reduce the pressure low enough that the water would become a gas and in doing so, make a lot of noise and was called cavitation.
When the sub commander did this, it did mean the ship could go very fast, but was noisy as hell and anyone near would know they were around, but if someone shot a torpedo at you and you had to get out of range…
Before readying the other reply I thought something like this might have happened and disrupted the smooth laminar airflow.
I know aircraft have over speed and under speed warnings for propellors too, but I thought that was more to do with not breaking them than 'grabbing the air ’ efficiently. Supersonic propellor tips aren’t a good idea.
Cavitation occurs in a liquid. When you’re pushing air, you may bump into other types of problems like stalling. If the fan is connected to a pipe, you can also get repeating surges of airflow.