"Perpetual Force" Air Molecule Motor Part III

Still on the topic of the very significant force imbalance obtained in the eleven silux-model cases previously discussed, I decided to further investigate possible mundane explanations for this imbalance.

Pressure difference?

Could there have been a systematic starting pressure imbalance? Let's investigate that:— 

The center of gravity of the foil shown in Fig 2 is represented by the blue line, at the start of the simulation. The area above the line is 5.33333 × 20 cm² and the area below is 4.66667 × 20 cm². So if air pressure is exactly balanced above and below the foil, we should have a theoretical ratio of 5.33333/4.66667 = 1.142855, for the number of molecules above the line divided by the number of molecules below the line.

Fig 5. Checks for any systematic starting pressure imbalance

After counting the molecules for the starting configurations of all the cases analysed in Fig 4, I got the results tabulated in Fig 5 above. This shows that in only four of the eleven cases was there an above average starting pressure on the lower side of the foil. There was a deficit in the other seven cases. So a systematic pressure difference can be ruled out as an explanation for these results.

Boundary Effects?

In order to further investigate boundary effects I re-made the model with a larger container (was 20 × 10 cm², now 25 × 15 cm²). The foil was the same except for its ends, which were truncated vertically. This is a fairer representation of a small portion of what in reality would be a far longer foil than is being modelled here.

Fig 6. First run for re-made silux model, with larger container

Fig 7. Results for further cases run with re-made model

Results

Results of the first case run are shown in Fig 6 above. As before, I ran another ten cases, summarised in Fig 7 above. Ultimate upwards movement still occurs in 9 out of 11 cases. In only one other case did the foil move to within one foil thickness of the lower boundary. In that case a boundary effect was occasionally visible, i.e. molecules were sometimes seen to impact directly more than once between the lower boundary and the foil. Even though the foil did not move fully down (whereas it did in two other cases), and it eventually moved fully up, I decided to discard that case as inconclusive, replacing it with another case.

How significant are these results? I'll look at that next.