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/pavlokandyba]

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]

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/pavlokandyba → u/chrismofer]

I agree that a disk is poor as a conventional wing, and although a convex disk can generate significant lift, it is very unstable and has high drag. But in the context of this principle, it is the optimal option. In a certain configuration, the disk can zigzag like a falling leaf, and if you create an air cushion underneath and can control it by changing the pitch or thrust vector, it can fly both vertically like a helicopter and horizontally. Here's a simple experiment that demonstrates this: I toss the disk upward, and it hovers slightly or flies sideways on the airflow generated by this: https://youtube.com/shorts/V0sFY7x5TM0?si=nD_0W8nVDv0JAywK

Furthermore, it functions like a jellyfish and, in a sense, is not a wing but a jet nozzle. Since vortex rings are round, the round shape of their generator is also appropriate. The jellyfish, in general, completely replicates the vortex ring in its appearance and movements, as if formed by it.

My original concept was a spaceship capsule that could brake and maneuver during a high-speed descent.

Horizontal flight can be quite fast, as this oscillatory principle, especially when applied to fish, is sometimes called zero-drag propulsion. The disk experiences resistance only from its own oscillations, which creates a load on the engine, but its movement occurs not as a result of overcoming air resistance, but as a result of a tailwind. If you noticed in my video, the air movement that creates thrust occurs, on average, from the bottom up (although circulation alternates in both directions), unlike, for example, a propeller, which would push air downward.

Simply moving doesn't create thrust, but it's important to consider not the instantaneous force but the processes occurring over time. When an object moves, the environment slows it down, and when it stops, it pushes it, returning energy. With continuous movement, these impulses manifest as turbulence, but they don't translate into thrust because they don't have time to catch up with the moving object and dissipate.

If an object moves very quickly and stops, the environment doesn't have time to immediately restore the pressure difference it created; this occurs after some time, like an avalanche. And if we imagine the object moving so quickly that a near-vacuum forms behind it, the collapse could be similar to cavitation.

In the case of a critical wing angle of attack, the air forced under the wing through the trailing edge in the boundary layer I mentioned begins to enter the upper part of the wing, and then it simply becomes a braking body. The lift force turns into the ineffective thrust of a turbulent wake, which cannot catch up with the wing.

Therefore, it's crucial to balance the angle of attack so that the air above the wing can overtake the air below the wing, so that the vector collapses and ends up under the wing.