Is this bladeless air flow idea possible in theory?

Soldato
Joined
12 Oct 2003
Posts
4,027
I was just thinking about this idea again after seeing the dyson bladeless fan thread, we know air is full of moving molecules and atoms bouncing around in all directions, well what if you could get them to all move in the same direction?

I was thinking a specially designed surface and enclosure, perhaps down to micro scales at just the right angles, it would start to control some of the ones that hit at the right angle and create a general flow in one direction.
 
Caporegime
Joined
30 Jun 2007
Posts
68,770
Location
Wales
the dyson still uses a fan(well impeller iirc)

But there is a solid electrical one that still has "fins" but no moving parts.

microfan1f.jpg



http://www.physorg.com/news125057974.html


I was thinking a specially designed surface and enclosure,

chimney? As long as the air is warm/hot it will make a draft :p
 
Soldato
Joined
18 Oct 2002
Posts
2,953
Location
Greater Manchester
I was just thinking about this idea again after seeing the dyson bladeless fan thread, we know air is full of moving molecules and atoms bouncing around in all directions, well what if you could get them to all move in the same direction?

I was thinking a specially designed surface and enclosure, perhaps down to micro scales at just the right angles, it would start to control some of the ones that hit at the right angle and create a general flow in one direction.

So you are saying can we make a jet and control the flow of air using the science of aerodynamics?

if so, then yes we can, it's just quite tough to get the air to all go in the direction you want it to, unless its all occurring inside a totally sealed vacuum or over a VERY short distance. Turbulence is a bitch :)

While I'm guessing this is just a random thought (I have those), I was wondering what you were thinking of in terms of application? If it is a replacement for computer fans and things, I would suggest that perhaps simply replacing the blades with jets of air would be fairly difficult to achieve, certainly no easier than a bladed fan and almost certainly much noisier and more complex.

Effectively what you want to do is create a vortex induced vacuum effect at a localised spot in a computer case (which is what a fan effectively does), while its interesting, *something* still has to be moving to do this, be it the nozzles generating a high pressure air jet, or the blades of a fan moving the air around them, EDIT or the "blade-less" Dyson fan you referred to initially.
 
Associate
Joined
25 Oct 2009
Posts
576
Location
York
I doubt very much if you could pull it off, you'd need some sort of directional push and the only ways to do that without a central motor (afaik) are to use magnets or have it on a cogwheel/belt-driven system.

The former is a bad idea when surrounded by other electrical equipment and having no shielding and the latter being a bad idea if you're wanting to save space (as I assume you would).
 
Soldato
OP
Joined
12 Oct 2003
Posts
4,027
chimney? As long as the air is warm/hot it will make a draft :p

I was thinking on the small scale using natural air movement, when the gas particles hit specially design micro channels they bounce back and forth between the sides and eventually move in one direction out the end so creating a air flow.

Edit: im talking no moving parts, just the right design and shape that gets the tiny motions of gas (pressure) to all start going in the same direction!
 
Last edited:
Caporegime
Joined
30 Jun 2007
Posts
68,770
Location
Wales
I was thinking on the small scale using natural air movement, when the gas particles hit specially design micro channels they bounce back and forth between the sides and eventually move in one direction out the end so creating a air flow.

Not going to happen really. (

and even if you do manage it the amount of air flow will be so small that it would be over ridden by any disturbance in the air or pressure change.
 
Soldato
Joined
18 Oct 2002
Posts
2,953
Location
Greater Manchester
I was thinking on the small scale using natural air movement, when the gas particles hit specially design micro channels they bounce back and forth between the sides and eventually move in one direction out the end so creating a air flow.

How are you going to control the initial direction of flow of each particle? Even if you can "trap" them in a channel (how do you allow for the effects of restitution / friction etc?) and make them "bounce" from side to side, given just how many particles we are talking here, some will have an initial momentum meaning they will travel one way down the channel, others will go the other way, while there is a chance others still will simply not travel in either direction and bounce between each side of the channel until entropy does its work.

All of this is also an incredible over-simplification of what we are actually talking about here, my description works IF you consider the component particles of air to be little spheres floating about in space... clearly that's not a reasonable model to actually work with in reality...

Aside from the fact that generating channels that small is one heck of an engineering feat!
 
Soldato
OP
Joined
12 Oct 2003
Posts
4,027
One end will be different in design to the other, the difference should create an overall effect which makes the air go the way you want even though there's a lot of randomness, even a tiny difference should in theory cause air to flow, it just takes the right design.

Doesn't this idea violate the second law of thermodynamics :D

I don't think so as you're using the energy that already exists and just making it add up and go where you want, though i know entropy is a problem, i don't think it should be here.
 
Last edited:
Associate
Joined
6 Feb 2008
Posts
1,750
it would start to control some of the ones that hit at the right angle

I think this is where the idea starts to go wrong. The only simple way I can think of to explain it is using a snooker/pool table. Imagine the cushion on the table is your "micro-scale/fin", and the balls are air particles.

If you were to roll a load of balls (air particles) in one direction and bounce them off this cushion, they would have course keep going in that same direction. The problem comes when the balls are hitting the cushion from all directions, they will simply bounce off and keep going in all different directions. Ones that hit perpendicular will come back in the same direction they came from. No matter how small your "fin/scale", this will still happen.

Unless the fin was able to know which way the next particle was goin to hit from and adjust to fire it off in the same direction, it wouldn't be theoretically possible.

Edit: Quick answers above saying the same thing in a more scientific way me thinks.
 
Last edited:
Soldato
OP
Joined
12 Oct 2003
Posts
4,027
Isn't a funnel like shape at one end enough to get some difference going and movement?

That may be too simplistic but we're dealing with tiny scales so who knows how the gas will behave, it may be that enough bouncing is going on that at any moment the difference is great enough that the gas will flow out the end and create a constant net effect.
 
Caporegime
Joined
30 Jun 2007
Posts
68,770
Location
Wales
Isn't a funnel like shape at one end enough to get some difference going and movement?

That may be too simplistic but we're dealing with tiny scales so who knows how the gas will behave, it may be that enough bouncing is going on that at any moment the difference is great enough that the gas will flow out the end and create a constant flow.

problem is for every 1 particle that bounces "down" the channel there will be another particle bouncing up it.
 
Soldato
OP
Joined
12 Oct 2003
Posts
4,027
problem is for every 1 particle that bounces "down" the channel there will be another particle bouncing up it.

I know thats what i thought at first but the magic should come in the difference, if the out is smaller than the in and designed different to deflect away while the in side allows for more to enter, it should flow.
 
Caporegime
Joined
30 Jun 2007
Posts
68,770
Location
Wales
I know thats what i thought at first but the magic should come in the difference, if the out is smaller than the in and designed different to deflect away while the in side allows for more to enter, it should flow.

but there would be no way to make the difference.

There are so many and all going in random directions that you could never produce a over all net drift.


Your channels could only ever be designed to channel particles coming from a very narrow range of angles and speeds for every one that hit it just right to be sent down there would be millions of miss hits and some going the exact opposite way.
 
Soldato
Joined
17 Jan 2005
Posts
3,822
Location
London
A pulse jet has no blades yet creates a good bit of airflow, makes a teeeeeeny bit of noise though and gets a bit warm. Makes it pretty much useless for a fan although you could use a small one with a nicely insulated handle for a hairdryer :D
 
Soldato
OP
Joined
12 Oct 2003
Posts
4,027
but there would be no way to make the difference.

There are so many and all going in random directions that you could never produce a over all net drift.

Your channels could only ever be designed to channel particles coming from a very narrow range of angles and speeds for every one that hit it just right to be sent down there would be millions of miss hits and some going the exact opposite way.

Yeah it's quite a problem, i doubt that it would work well even if it did.
 
Caporegime
Joined
30 Jun 2007
Posts
68,770
Location
Wales
A pulse jet has no blades yet creates a good bit of airflow, makes a teeeeeeny bit of noise though and gets a bit warm. Makes it pretty much useless for a fan although you could use a small one with a nicely insulated handle for a hairdryer :D

still uses an external power source not just passive shaping :p
 
Back
Top Bottom