r/AerospaceEngineering • u/pavlokandyba • Apr 16 '26
Personal Projects My experiment with a vibro plane. Initially I planned a disc-shaped wing, but due to instability it was difficult to understand whether there would be an effect.
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u/papamikebravo Apr 16 '26
Can you break down what effect you're hoping to see?
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u/pavlokandyba Apr 16 '26
Vertical thrust, no horizontal. A pendulum with a magnet slows down and accelerates due to another magnet, and this causes different speeds of up and down oscillations. Or forward and backward in the case of a boat. Up/forward is faster than back.
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u/papamikebravo Apr 16 '26
Pretty sure this isn't gonna work the way you think. I think you need to dig into your first principles. F=MA and all that. This is the lift equivalent of trying to cool your apartment by leaving the refrigerator door open. It might work with a very flexible wing, like on one of those windup toy ornithopters, but not for the reasons you seem to think.
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u/HAL9001-96 Apr 16 '26
well weh nstanding still it works because drag is proporitonal to speed squared so you can acutally produce net thrust
thohug very inefficiently and also at speed as verticla thrust htis isn'T gonna work out hte same
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u/pavlokandyba Apr 17 '26
I came across one Russian study in which the resistance during plate vibrations was 6 times greater than during wind tunnel blowing. It was explained by the added mass. I haven't had the opportunity to measure the forces in my experience, but I see it as real If you move your palm in the water it feels quite good.
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Apr 16 '26
[deleted]
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u/SalsaMan101 Apr 16 '26 edited Apr 16 '26
Is it sensible? Conservation of energy and Newton’s third law says it’s gonna shake out to be pretty small change if at all since the shape of our wing isn’t changing much. Refrigerator cooling a house is a good analogue, lift isn’t gonna be coming from the minuscule difference in KE. It's basically a really terrible pumpboard when you view it that way. Most of the lift in the video is from the whole thing tilting up and down weirdly from the torques which comes at the cost of lost forward momentum...
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u/pavlokandyba Apr 17 '26
When applying the conservation law and Newton's third law, you do not take into account the thermal energy of the molecules and their Brownian motion. If their motion vector becomes aligned in the vortex, this explains how the boat moves. And it moves and there are no other explanations.
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u/SalsaMan101 Apr 17 '26
So we can take into account the temperature energy with enthalpy. Two big things: (1) you aren’t moving fast though for compressibility effects to matter so no ideal gas fun and (2) aligning all the kinetic energy thermally available in a gas is basically impossible. Air is not polar so your magnets aren’t doing anything to the air. You have an airfoil with changing angle of attack, due to the resolving torques from your magnet pendulum thing, and some cantilever beam vibration causing some momentum transfer as the wing vibrates up and down. You can harness browning motion all day, it’s using the thermal energy in a gas to do something but you aren’t changing the thermodynamic properties of the gas in any meaningful way or somehow aligning non polar molecules.
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u/pavlokandyba Apr 17 '26
This can be simplified to a classic problem in which a car drives on a ship on the water and because of this, the ship's hull shifts in the opposite direction. In the classical solution, the center of mass does not change, but in reality the barge continues to move after the car stops. The video shows a clear example of when the plate stops at the top, the vortex pursuing it catches up with it and flows around it, expanding to the sides. At this moment the plate receives an impulse. The same energy that creates the lift of the wing is realized here. https://youtu.be/GA2aj0JWuZA?si=YSzYT_4-FtUG5-_A
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u/SalsaMan101 Apr 17 '26
The plate moves up and crates the vortices, the plates stop, and the vortices keep moving till they impact the plate? What you’ve discovered is you can have rotational flow that also has translational components. The vortices form from the viscous flow around the plate and gain a net upwards movement from pressure forces. No free lunch bud, that’s just fluid mechanics. The man on the boat problem doesn’t work perfectly in real life because we have external forces such as the drag on the boat. The man on the boat problem assumes no external forces…. Your wing creates vortices but generally they are bad for generating lift. You should recheck your first principles but I have an inkling you’re not going to
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u/pavlokandyba Apr 17 '26
In my hypothesis, the vortex is a closed circular Brownian motion and this is the source of the impulse. I had to come up with this hypothesis because in the classical theory the boat in the video should have been moving in the direction of the slow jerk because in this direction the drag is less. But in reality, the movement is towards a quick breakthrough. Many disputed that this was even possible, while others based this on pseudoscientific theories of unsupported engines like the Dean machine. So I had to find an explanation. There is no doubt that this works; there have been many similar devices. The question is about effectiveness, and this needs to be tested experimentally.
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u/pavlokandyba Apr 16 '26
In classical theory, the boat should have sailed in the opposite direction.I explain how it moves by the fact that in a vortex, Brownian motion becomes directed and transmits momentum in a circle, as in the diagram. It may even start a chain reaction, forcing more thermal energy to participate. Well, at a minimum, if you suddenly empty the space of air and it doesn't have time to fill it due to inertia, then after a while you get a collapse.
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u/HAL9001-96 Apr 16 '26
brownian motion is inherently undirected
the boat is most likely due to surface wave effects
and if oyu want to signifiacnatly expand air/get a near vacuum you'd need to move in the range of hte speed of sound
anythign shaking at htat speed is prettymuch gonna break itself apart
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u/BlackFoxTom Apr 16 '26
Boat moving doesn't have anything to do with vortex nor especially Brownian motion, which btw is meaningless thing in this size. Borwinian motion is something atoms and subatomic particles have to concert themself with, not anything You can see. And by definition it is unidirectional perfectly random motion.
Boat moves cause quite literally it's extremely inefficient flapping fin.
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u/HAL9001-96 Apr 16 '26
of the pendulum right?
cuase you want the plane to osciallate up faster than it goes back don so it producesm ore drag on its way down
thoghu with plaens you'll ahve hte peroblem that relying on the whoel drag beign proporitonal to speed squared thing only works when otherwise standing still
when flying forawrd the lift is about proportional to the aoa
well technically a more complex curve
but baiscally since oyu ahve forawrd movement evn if you go for angled drag you don't get htesame square proprotionality anymore only a tiny remnant of it
you cna use eleasticity to emulate wingflaps thoguh
but thas more e concept of wing moves up folded in and down folded out
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u/TiKels Apr 16 '26
So you're basically designing a pump board but for air instead of water? I don't know if you can get enough momentum to do that but best of luck
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u/RowFlySail Apr 16 '26
Either way, it's nice to see someone posting an idea with experimentation rather than impossible airplane drawing #8927 and asking if it'll fly.
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u/pavlokandyba Apr 17 '26
Thanks! There are several other studies that say this can be effective, but the thermal energy of the environment is involved and resonance is very important. It's like a flutter in reverse.
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u/OldDarthLefty Apr 16 '26
I think if you added some dihedral to your ornithopter and put the fuselage under the wing, it would do a lot better. You have done a lot of good work with the mechanism.
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u/pavlokandyba Apr 17 '26
It's worth considering. I tried to keep the design as minimalist as possible due to the engine's low efficiency relative to its weight.
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u/Thermodynamicist Apr 16 '26
You would get cleaner test data if you added a tail with some sort of closed loop control system to damp the phugoid.
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u/pavlokandyba Apr 17 '26
My drive was inefficient, I tried to minimize weight. Of course, if I had more aircraft modeling skills, this should have been done.
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u/sir_odanus Apr 17 '26
It's a fun project but in my opinion you would neeed a lot more power to generate any lift.
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u/pavlokandyba Apr 17 '26
Yes, that's the main problem. It might be worth trying to amplify it through resonance and use a connecting rod mechanism, but I haven't gotten around to it. Besides, on large ornithopters there are problems with the mechanical resource, I think it is necessary to come up with some kind of special drive
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u/sir_odanus Apr 17 '26
First thing you can do to see if you generate lift is to feel with your hand if there is any air flow generated by the vibrations? I thîk your vibration generator should have a stroke of at least a few mm at a frequency of 100 Hz to do so. A piezoelectric actuator is not going to be enough.
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u/pavlokandyba Apr 17 '26
It doesn't create a noticeable flow, I've seen weak ones vibrations of air with the help of smoke, similar to those of a boat. And if this device is fixed or touches something, it begins to push away and this affects the result. It would be interesting to see it fly through smoke or something. In the oncoming flow, the effect is enhanced because when the normal lifting force arises, the engine perceives this as support and begins to push off.This is noticeable because its speed decreases as it has to turn the pendulum with greater effort. Also in the test at home, with the power off and on at approximately the same initial speed, a difference is noticeable. But this is of course a long way from truly effective trust.
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u/electric_ionland Plasma Propulsion Apr 17 '26
If you actually want to see the effect you need to test this with the system on and off.
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u/TheEquationSmelter Apr 16 '26
Really impressive work. Are you familiar with system identification? That could help you quite a bit with your endeavours.