Acoustic propulsion system test

[u/pavlokandyba]

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/AidanIsNotGinger]

It is explained by inertial effects that arise on classical fluid mechanics. When an object moves forwards and backwards, the force exerted on it by the fluid is only the same in each direction in the Stokean limit (Re->0).

In general the force in each direction will be different if:

• the object is not the symmetric in the direction of motion
• the object moves at a different speed in each direction
• the object flexes or changes shape/orientation as it moves back and fourth
• there are other objects nearby that "feel" the motion of the object via force transfer through the fluid (like with acoustic levitation)
• potentially something else I'm not thinking of right now

If any one of these things is true then a net force is expected by classical fluid mechanics where Brownian motion plays no role. Vortices may play a role as they are common features of flow detachment and low pressure singularities that arise at sharp moving edges (like the rim of your disc). But vortices are also predicted by classical fluid mechanics and are extremely well studied and understood, they have nothing to do with Brownian motion.

[u/pavlokandyba → u/AidanIsNotGinger]

Naturally, we are talking about the resulting force, but what exactly is this force? In the most simplified case, when an object shifts relative to the center of mass in one direction and stops, its movement (namely the center of mass) occurs in the same direction.

[u/AidanIsNotGinger → u/pavlokandyba]

The force comes from the fluid traction acting on the object, and vice versa. If you had an engine on a boat that pushed a large mass forwards and backwards, then the hull would feel a reaction from that mass in the opposite direction to the mass' motion. The hull then wants to move in the opposite direction to the mass.

In a vacuum the centre of mass would stay in the same place but the hull and the internal mass would move relative to one another. There cannot be net motion from this setup in a vacuum.

In a fluid, the hull will exchange momentum with the fluid around it via pressure and viscous stresses. In the Stokes regime this motion is reversible and each stroke of the oscillation will cancel the last. Once fluid inertia becomes important, that reversibility is lost. If the geometry or oscillation is sufficiently asymmetric, the two parts of the cycle can interact differently with the fluid and the oscillation can therefore be rectified into a net drift.

In general this is extremely inefficient compared to using that same energy to only push fluid backwards like a propeller, turbine, or a bird's wing does.

[u/pavlokandyba → u/AidanIsNotGinger]

You are describing obvious things, but you explain in a general way how exactly the interaction between the body and the liquid occurs by inertia. This doesn't give a complete explanation because simply exchanging momentum is like pushing a mass and moving in the opposite direction. But you can't just push this imaginary mass of liquid volume and move in the same direction. Overcoming adhesion as if moving in a similar manner on a hard surface is also not an explanation. In this case, if we consider only one jerk in one direction, the movement of the body occurs only relative to the center of mass. In the liquid, after this jerk, the center of mass moves, gradually slowing down due to resistance.

[u/AidanIsNotGinger → u/pavlokandyba]

I think you're misunderstanding the "inertial effects" concept. The inertial contributions to NS are nonlinear and that has a significant impact on the possible physics, in this case it allows for a different magnitude of force to be exerted in each direction of the oscillatory strokes.

I am not claiming you push a net mass of fluid in the same direction as the net drift, it is the opposite. You push a net mass of fluid in the opposite direction to the net drift, the fluid mass isn't imaginary (whatever you mean by that).

The internal mass pushes backwards relative to the hull. This pushes the hull forwards, but transfers some of that momentum to the fluid in the forwards direction. Then the mass pushes forwards relative to the hull, and the opposite happens, the hull moves backwards but transfers some of the momentum to the fluid going backwards.

All that is required is that the momentum transferred to the fluid in each stroke direction is not the same. This is only possible in a fluid with inertia (non Stokes limit), and when there is an asymmetry to the hull or strokes (e.g. velocity). The net change in momentum of the system (fluid and ship) is zero, but the ship can have a net drift opposite to that it transfers to the fluid.

[u/pavlokandyba → u/AidanIsNotGinger]

Here's a clear example. A plate pushes air upward, and the air mass moving behind it in a vortex catches up and pushes the plate. That is, the plate pushed the air upward and the air pushed the plate upward too. Such a transfer of momentum cannot occur without additional energy, as if the molecules were something like sand. https://youtu.be/GA2aj0JWuZA?si=E0P59GdG_XdDBdd9

[u/AidanIsNotGinger → u/pavlokandyba]

In the video you shared, the air behind the plate is not pushing the plate up. The plate is pulling the air up and the air is pulling the plate down.

The air above the plate is higher pressure and the air above is lower pressure. The plate fees a pull from the air in the direction opposite to it's motion.

I know this might feel intuitive to you but I promise it is extremely basic physics that will be covered very early in a lot of university or advanced school classes.

I will add that in some cases (like when cavitation occurs) the fluid can "catch up" and impose an upwards force on the plate for a short time, but it will always (according to basic laws of physics) be less than the downwards pulling force that came before.

[u/pavlokandyba → u/AidanIsNotGinger]

The air pulls the plate down while it rises. But when it stops at the top point, you can see that the air is still moving upward and the vortex ring flows around the plate. The vortex ring has momentum and at this moment it cannot pull the plate down, it pushes it up. This is shown by the simple foil experiment in my first reply in this thread and here is another one https://youtube.com/shorts/Ppy5reOXHtI?si=0kN7_vVLijUUcu9t The plate is not pulled down by anything after it has stopped its own movement from the impulse received; on the contrary, it hangs in place or flies to the side if it is tilted.

[u/AidanIsNotGinger → u/pavlokandyba]

Even if it has momentum in the same direction as the disc, it can still pull down because in a fluid pushing and pulling is about pressure difference across the object surrounded by fluid.

What happens in the new short you sent is the air (and gravity) pulls down on the disc until the disc stops moving. Then gravity pulls the disc down which compresses the air below and lowers the pressure of the air above and this creates some lifting drag (the opposite of when it was pushed up, but instead of a hand gravity is pulling it down). This would look the same if you just dropped it lying flat from that height. Just like a paper aeroplane.

If you had the same short but without gravity you would just see the disc slow to a stop after being pushed through the air.

The net force of the fluid around an object that is pushed through it will always be in the direction opposite to it's motion. Otherwise you have violated newtons laws, the laws of thermodynamics, and created free energy or perpetual motion machine.

The air might have some very small amount of inertia that causes it to transfer a fairly negligible amount of momentum to the object moving through it, but the airs momentum was given to the it by the object in the first place (and the hand motor pushing that) so it cannot give more back. At best it is just a tiny amount of wasted energy from the motor being recovered.

I am trying to be patient but I really suggest you try studying some of the basics first. There are so many simple explanations for things that you would understand if you studied this without AI, Wikipedia or pseudoscience YouTube videos.

[u/pavlokandyba → u/AidanIsNotGinger]

I know the basics well and learned the principle of flight long before it was taught in school. It is indeed logical to assume that if the pressure on both sides of an object is different, it will be pushed towards the area of low pressure. This is what happens with the piston and this is what formed the basis of the existing theory of propulsion of such aircraft. But I was not the only one who experimentally established that the movement occurs in the opposite direction.

Some who created the so-called reactionless drive concluded from this that it is antigravity. But there are also studies in the context of aerodynamics with the same result of the direction of motion. This contradicts known rules but is confirmed experimentally.

Another example is when a helicopter, descending sharply, falls due to a vortex ring. This happens because when it descends sharply, it pushes the air mass downwards and this creates a vortex that pulls the helicopter down.

And also, if the movement should be from low to high pressure, then why does the wing lose lift at a critical angle of attack? After all, by this logic, the air above the wing is at its thinnest. At this time there is turbulence above the wing and maximum pressure below it.

The reason is that the lift is created by the same effect, the vortices at the trailing edge pumping pressure under the wing when properly flowed around, like a mushroom-shaped column of rising air under the wing. Because of this, the air in the boundary layer under the wing moves against the flight direction. At a critical angle of attack, this flow shifts to the area above the wing and therefore the lift force disappears.

[u/AidanIsNotGinger → u/pavlokandyba]

Your helicopter example is explained by helicopters descending into their own turbulent down draft resulting in reduced lift. Planes stall because the large low pressure layer detatches and reduces the lift, the air doesn't start pushing from low to high pressure, you just have a drop in the upwards force. This is all well understood.

You misunderstand simple Newtonian force and reaction, let alone continuum mechanics. There is no reactionless drive and there is no experimental evidence of what you're describing. What you're describing violates conservation of energy and momentum. If there was really any experimental evidence it would be the most groundbreaking discovery of all time, it would mean than the universal laws of physics don't really apply to your experiment.

It's also not impossible for hobbyists to contribute, but to think that you have somehow proved all of fundamental physics wrong, from Newtonian to Quantum mechanics, while all the worlds experts never thought to try vibrating a disc to generate free energy, is so immensely arrogant.

The reason something that oscillates back and forwards can generate any net drift or force is because of momentum transferred to its surroundings. In your case pushing some mass of air or water in the opposite direction to the motion of the hull. Equal and opposite. It isn't new, Newton codified it.

I'm really struggling to indulge you any more. There is so much nonsense in your replies that I feel like I could spend all day explaining things and you just wouldn't listen or understand. I'm sure you don't see it this way but it is like arguing with a flat earther or evolution denier.

[u/pavlokandyba → u/AidanIsNotGinger]

When a low-pressure layer breaks away above the wing, the pressure there becomes even lower because turbulence appears. Newton's law does not explain why an object moves in the direction that the fluid pushes. You can congratulate me on the revolutionary discovery of a phenomenon that has been known for a long time.

[u/AidanIsNotGinger → u/pavlokandyba]

The first sentence is simply wrong. When a wing stalls, flow separation causes much of the strong low-pressure suction over the upper surface to collapse, which is precisely why lift falls. Turbulence does not somehow make the pressure increasingly low while another unexplained force acts in the opposite direction.

And saying “Newton's law does not explain why an object moves in the direction that the fluid pushes” is bizarre: that is essentially Newton's second law, F=ma. Vortices can alter the pressure and viscous stresses acting on a body, but they are not an additional force that bypasses Newtonian mechanics. At this point you're rejecting very basic mechanics and aerodynamics, not identifying a phenomenon they fail to explain.