"Perpetual Force" Air Molecule Motor Part II

Modelling of further cases

I modelled ten more cases of the foil in a container with air molecules, as discussed previously. The foil was held stationary for a further 1s, 2s, etc up to 10s, before being released, in order to obtain a different random starting distribution of molecules for each case. 

Results

In all of these cases also, (summarised in the spreadsheet below) the foil moved generally upwards in the container, reaching velocities between 0.02138 and 0.09513m/s just before hitting the upper boundary. On only one occasion did it move to (just) within one foil thickness of the lower boundary, and even then I didn't notice any molecules impacting directly between that boundary and the foil. Boundary effects do play a part in accelerating the foil near the end of the simulation, but only because it has already moved to within about half a foil thickness from the upper boundary.

Fig 4. Spreadsheet of results for foil in container with air molecules

Discussion

Is this a credible result, i.e. would such a device really work? Could it really deliver a perpetual net force, and energy, from nothing more than "thin air"? 

The probability of the foil moving to the upper boundary 11 times in a row by chance is the same as tossing a coin to get 11 heads in a row, i.e. 1 in 2^11 = 1 in 2048 = 0.0004883. Still, these eleven "spot-check" results are not fully conclusive. The three main reasons for that are the unrealistic modelling of the air molecules, boundary effects, and the 2D rather than 3D analysis.

The physical data for the air molecules used in the model are:—

radius 2mm, mass 0.261 gram, initial velocity 1.414 m/s. 

These data are vastly different from the (approximate) data for real air molecules (mostly N2 with some O2):—

radius 0.00000025mm, mass 4.8 × 10^-23 gram, rms velocity 500m/s.

Also the foil mass, modelled at 1kg, is far heavier than would be the case for a foil of the correct scale interacting with real air molecules.

Nevertheless, I find these results so far to be interesting. They do suggest that further work on this idea would be worthwhile.

"Perpetual Force" Air Molecule Motor Part I

Can the movement of air molecules be exploited?

Fig 1. Specification drawing for foil with tapered holes
Alt 2 has foil thickness 0.05 micron, and hole dia 0.01 micron at upper surface; 0.002 micron at lower surface.
Alt 3 has foil thickness 0.5mm, and hole dia 0.1mm at upper surface; 0.02mm at lower surface.

I'll now say something about the foil shown and specified as Alt 2 in the above specification drawing, which I first posted on 17 September. I wanted to see whether a foil like this would experience a net force just from being immersed in air at normal temperature and pressure.

Operating principle

The proposed operating principle was similar to the Casimir-force foil, except that instead of zero-point energy fluctuations, it would be air molecule impacts delivering energy/momentum to the foil — but again to a higher degree on the lower surface. Air molecules arriving at the upper surface would generally enter the holes, and would be reflected from the sides of the holes, exerting only small forces resolved vertically, before (probably) exiting at the lower surface. Air molecules arriving at the lower surface would be more likely to hit that surface, because of its decreased hole diameter, exerting large forces resolved vertically.

No supplier

As already stated, no-one was able to supply any of the foils described in the specification drawing; not even Alt 3, which was a much larger version of Alt 2, and hence would have been much easier to make. Alt 3 was also intended for air molecule impacts, but in a fairly high vacuum, where the mean free path length of the molecules would be a lot higher.

Silux model

Since I was unable to test this idea in any physical experiment, I decided, later on, to see what could be done with a silux model. (For anyone unfamiliar with silux, see my posts of 7 April and 13 April 2014 on this blog).

The file folder named "models" that comes with the silux program includes a model named "Model and Simulation of an Almost Ideal Gas", which is also described further in the free PDF document named "Samples 2D" (page 49). This model demonstrates how the impacts of individual gas molecules, when aggregated together, produce an upward force that balances a weighted piston within a cylinder. (It also demonstrates visually how molecule velocities vary naturally over time — presumably a correct Maxwellian velocity distribution is eventually achieved, although it would take a lot of work to verify that).

I adapted this model to check the effect of air molecule impacts on a small, non-optimised portion of a foil, as shown in Fig 2 below. 

Fig 2. Silux model of a small portion of a foil with tapered holes,
in a container with 200 air molecules

Model details

I started with the 100 molecules in the original model, duplicating them again for a total of 200. Each molecule has a radius of 2mm, a mass of 0.261 gram, and is originally started at a velocity of 1.414m/s, as originally created by silux. The seven triangles are made into a single foil of mass 1kg, constrained by a macro against sideways or rotational movement. Movement up or down is permitted. All molecular impacts, to other molecules, or the foil, or the fixed container, are always 100% elastic. Gravity is inactive. The container "volume" in this 2D model is 20cm × 10cm = 200cm².

The simulation is started with the model configured as above. This is after a few seconds of prior running with the foil also held fixed, to ensure that the air molecule velocities are "randomised" before the foil is released.

Fig 3. Silux model at end of simulation

Results:

After 3.981 seconds of simulation time the foil is about to hit the upper boundary of the container, as shown. By then it has moved 0.03883m upwards, and has an upwards velocity of 0.02612m/s.

This looked reasonably promising, so I decided to look at some more cases, which I'll discuss next time.

I'm Back!

The first hiatus is over: I'm now back.

Here is a brief update on the three issues that caused the hiatus. Without going into too much detail:—

First issue: Should have been completely resolved by now, but isn't. That's no real surprise, in this modern world of ever-decreasing standards of performance. I still have some reason to expect a resolution by the end of the year.

Second issue: A health issue which now seems to have disappeared. Hopefully it won't return.

Third issue: Another initially hard to diagnose health issue. It was eventually diagnosed, and after minor surgery it's now resolved.

So all in all, things are not as bad as they could have been, and I intend to resume posting to this blog on about a weekly basis.