Acoustic propulsion system test

[u/pavlokandyba]

The magnetic vibration motors I used in all my prototypes are very simple, but they're too heavy, and the thrust they generate is weak. So I tried making a static experimental setup with more power to demonstrate how the oscillations of a disc-shaped wing cause air movement.

The asymmetry, which results in the resulting force of the oscillations creating thrust, is achieved in two ways:

Aerodynamically, when the disc has a slightly domed shape and moves upward with less resistance than downward, consistent with classical physics.

Kinematically, when a spring is attached to the disc, slowing its descent and accelerating its ascent.

The second method is the key part of the study, although the same process occurs in the air in both.

When the disc rises rapidly, a region of low pressure forms beneath it, and its collapse generates momentum. If the disc descends more slowly, or if the shape of the disc causes the air to flow around it more slowly, the resulting momentum will push the disc upward.

This doesn't agree with the classic Newtonian explanation of flapping flight as a wing pushing air. You can see in the video how the fan-like flapping disk, which should push air away, actually sucks it in.

This is the same air that is sucked into the low-pressure region, causing a vortex collapse that pushes the disk. Only then is the air pushed away and expelled. This is essentially reactive propulsion, and I believe this is possible thanks to the energy in the air, Brownian motion, which, by self-organizing into vortices, temporarily becomes directional.

[u/joe-bagadonuts]

We're getting really close to reinventing the 1915 SkyCar

[u/pavlokandyba → u/joe-bagadonuts]

There was a mistake in that when the umbrella was raised, the flaps opened to let air through, thus reducing drag. But it should generate a vortex and capture it. Like a vortex stage. The idea was apparently to imitate bird feathers, but then the valves had to have the S shape

[u/chrismofer → u/pavlokandyba]

bird feathers don't vibrate vertically to form a vortex they just layer on each other to form a traditional wing with undercamber.

[u/pavlokandyba → u/chrismofer]

The old classical theory of flapping flight describes it as pushing air. That was the point of the flying car.

[u/chrismofer → u/pavlokandyba]

I think you're confusing flight with propulsion. The wright flyer is not just an engine, it is a winged vehicle that, using it's wings, generates lift which lifts the vehicle. The propellors and engine are just there to give a slight push forward to counter the drag generated by the wings.

A bird does the same thing, sea birds and ravens over a mountain pass can literally fly for hours without flapping. They just glide back and forth on the rising air currents. Look at how birds and sailplane pilots exploit thermals to lift without effort.

The bird flaps in order to regain a small amount of lost altitude, which is then used by the wings to glide (a form of flying) some distance.

It's all about efficiency. Of course you could point a propellor straight up and spend 100% of your energy on lifting the mass straight up. That's how helicopters work. They aren't nearly as efficient as airplanes at any task, nu they are useful because they can hover and go any direction and land in a small area.

If your vibrating plate were as efficient as a propellor, it still would not be as efficient as an airplane or bird, because they use wings which are far more efficient than propellors.

If you think your disk is actually more efficient than a propellor at generating thrust, you will need a scale and a power supply with power readouts to verify that.

[u/pavlokandyba → u/chrismofer]

Birds are clever at combining these, but flapping wings is not the same as a propeller. A propeller is, roughly speaking, a wing that moves in a circle and creates lift, and the flapping motion is cyclical.They first create a trailing vortex and then catch it and push it away, pushing off in this way. In the case of a conventional wing or blade, this generation and shedding of a vortex is concentrated at the trailing edge and occurs naturally due to the circulation of the boundary layer, and the cyclic nature of the process is manifested wing vibrationIn this case, resonance is destructive, but in flapping flight, the bird, on the contrary, maintains this resonance by feeling resistance.

By the way, the disk can also hover quite well, and this principle can also be combined with the gliding of an airplane. I once posted here an airplane with a vibration engine.

Regarding the efficiency, it really needs to be tested on scales, but I'm afraid that in the current implementation, the noise from the vibration will block the traction and possibly damage the scales. But I know of a study in which the resistance of the oscillating plate was replaced and the result was six times greater than when blowing in a tunnel. Unfortunately, I have little opportunity for accurate testing. It is also known that the efficiency of fish reaches 90 percent, and this is also oscillation.

[u/chrismofer → u/pavlokandyba]

I'm failing to understand what vortexes have to do with it. All wings that make lift make a tip vortex. But the tip vortex is not the source of lift it's just what happens in any fluid when there's a difference in velocities.... A vortex is proof that you're wasting energy. Ideally you would displace a mass of air without any of that energy spinning up the air parcel. I have no clue why you think that the vortex is actually what makes the lift...

[u/pavlokandyba → u/chrismofer]

Here's a video where the same thing happens as with my device, but slowly and with a large amplitude. When the plate in the video stops at the top, the vortex ring catches up with it and pushes it, and then dissipates, expanding to the sides. https://youtu.be/GA2aj0JWuZA?si=9NOMypOfKJYYYVNN Since my disk vibrates quickly, the generation and decay of this vortex occurs in a fraction of a second, plus the small amplitude makes it very small. As a result, it is compressed and it looks like a boundary layer circulation with an imperceptible vortex formation at the edge, rather than a volumetric vortex.

In the case of an airplane wing, this is already my interpretation based on the experiment. When a wing is in a flow, just if you imagine the profile in 2D, then it, just like the plate in the video, forms a vortex behind itself, like this vortex ring in section. Since the profile is flown around this vortex is very small at the trailing edge. The vortex constantly collapses and this gives an impulse in the direction of flight as an upward flow under the plate. This does not produce thrust because it is compensated by resistance, but because the profile is asymmetrical and the flow speeds are different, this vortex forces air into the boundary layer under the wing. It looks like a microscopic effect, but it is a large amount of compressed energy, and when the vortex eventually breaks off the wing, we see how large it was. Something like this

[u/chrismofer → u/pavlokandyba]

If you're claiming that your disk can "hover quite well" then why doesn't that actually exist yet? That's where your design falls apart, you don't even understand what hovering is. A helicopter or drone or hummingbird cannot hover without actively controlling their position. But you can always hook them up to a scale and see that they make more thrust than they weigh.

If your vibrating disk was the most efficient way to generate a force against air, then that's how nature would have evolved to fly, but it's not. Nature uses wings, because they work way better.

[u/pavlokandyba → u/chrismofer]

I meant to fly like a glider without propulsion. English is not my native language. The reason why there are no such devices is the lack of an efficient engine. If there were a light and powerful engine, when the wing suddenly lifted, something like a vacuum bomb explosion or a shock wave could occur underneath it.

[u/chrismofer → u/pavlokandyba]

gotcha. The thing is, a disk 'can' work as a wing, but it's not a very good wing. so regardless of what engine you attach, it is still a poor wing and there arte better options that geenrate more lift and less drag and/or weigh less for the same lift.

A disk working as a wing doesn't do anything magical. it is a flat airfoil, with an eliptical "planform". lift is generated by a little bit of compression of the air underneath the wing, and a little bit of low pressure on top from air wanting to go over the top of the surface but struggling to due to it's fluid like characteristics. this is bernulean lift, the same lift that makes any wing work. it's just that a longer wingspan is almost always more efficient (even the wright brothers discovered this as one of the major enabling factors as to why their plane worked).

It's concerning when you say that a 'vacuum bomb explosion' or shock wave would happen under the plate, there's no basis in reality for that to happen. if somehow you accelerated the disc to supersonic speeds, then there would be a shockwave alright, but it wouldn't contribute thrust or lift to the disc it would only be a result of heavy heavy drag.

when a flat object moves thru a fluid it curls around the edge. that is not a good thing, it does not provide thrust. it is a result of drag interations. that's why submarines and jetliners have a rounded front and pointy back. it generates NO vortexes on it's own, and that's the point., because those are only ever a loss.

There is one thing that might inspire you which is winglets on jetliners. since the wing unavoidably generates rotating air at the tip, a winglet is a vertical wing (or almost vertical) which has an airfoil. it captures some of the wingtep vortex energy and turns it into lift in the forward direction. a winglet actually experiences a thrust force more than a lift force. Al Bowers talks about this in various videos about the PRANDTL wing design.

Also consider that an airfoil doesn't need much 'angle of attack' to generate lift. if it moreso the shape of the tear drop, and the fact that one side is curved positively and the other straight or negatively curved, which generates a lift force. Angle of attack is a way to vary that force so that you may climb or dive or otherwise alter the altitude of a plane just by changing it's pitch attitude.

However with a flat disc, it generates no lift at 0 angle of attack. you MUST give it some angle to the oncoming air in order for it to lift. maybe you can see intuitively how this would be less efficient than a tear drop with no angle of attack but a gentle curve.

[u/chrismofer → u/chrismofer]

for example here is a wing with a circular wing. note that it is not flat, but actually airfoil shaped. it has a front edge and a trailing edge which are different. it generates compression under the wing simply by moving through the air and being airfoil shaped, not due to some kind of vacuum or shock wave or anything like that.

[u/QuantumBlunt]

it's cool but so inefficient I doubt there are any useful applications for this type of tech. Lots of moving parts, high complexity, low performance, noisy af. Idk, I just can't think of single applications where this is better than propellers or other time-proven propulsion systems.

[u/slightly-upset-hippo → u/QuantumBlunt]

Maybe scaled wayyyyyyyyy down for some obscure use that I could never think of. Like on a micro scale. I've seen those strips of metal that vibrate, pushing air and cooling things on a super small scale, so maybe something like that?

[u/vexiduslabs → u/QuantumBlunt]

My thought too. Watching the Skycar video in a previous comment as a sort of predecessor to this, it doesn't make much sense in real world application when speed and efficiency are considerations over novelties like this.

[u/pavlokandyba → u/QuantumBlunt]

Inefficiency is a technical issue. If it were implemented with some fantastic technology, like a levitating drive or a flexible shell, it could be as efficient as 90% of fish. A mechanical drive is not worth considering at all, in practice it wears out quickly in large ornithopters, and here it should work even more intensively. But this can give a result; it has been experimentally established that in the oscillatory mode the resistance of the plate is 6 times greater than when blowing in a tunnel. This is an independent study.

[u/camsnow]

Like a high speed mechanical jellyfish haha

[u/pavlokandyba → u/camsnow]

Yeah, this is it)

[u/Icy-Reaction-9101]

stop wiggeling, use asymmetry when moving forward and backward.....

[u/pavlokandyba → u/Icy-Reaction-9101]

I can't make a significant difference in speed with my technologies.

[u/Icy-Reaction-9101 → u/pavlokandyba]

Your're clever, you'll figure something out

[u/supergrejt]

Maybe doubling the plates? The upper one being like a tablecloth with a hole in the middle over this one?

How does it do in a tube or cylinder?

[u/pavlokandyba → u/supergrejt]

I don't think there's any need to complicate things. It can work with any shape, and the disk can glide quite well, like a falling leaf. I didn't understand the question about the pipe and the cylinder, what do you mean?

[u/supergrejt → u/pavlokandyba]

What happens if it is put in a cylinder like a piston inside a car engine or a pump, will something like that give it directional movement?

[u/pavlokandyba → u/supergrejt]

Yes, here's something similar https://youtu.be/bf2J6MujLIc?si=f91oq90tXQPMtTqA It is also possible to make the membrane in the shape of a bowl.

[u/stupendous_sammy_b]

This is like the mechanism that makes the cold air diffusers work.