Hi Esa,
> the main thing of interest for those who wish to look at the Pöpel report is the report of "negative friction" - i.e. that the pipes, through which the water flowed, were shaped in such a way as to actually accelerate the flow of water, and to negate friction. Yes, that is interesting. > * > The spiralling copper pipe produced an undulating friction curve as the flow was increased. At some flows a negative friction was observed, as if water seemed to lose contact with the walls and fall freely through the pipe. How to interpret this remains to be seen. This is a particularly important observation for me. I have also noted an undulating resonance when winding helical and flat spiral secondary coils for high voltage experiments. To be safe, I would always wind the coil with a longer piece of wire than needed. Then I would measure the resonance of the coil to see where it was with regard to my target. I found that by cutting off a specific length of wire did not necessarily result in a corresponding increase in frequency. Sometimes the frequency of the coil would actually increase as wire was cut off. The increase and decrease of frequency would undulate even though the wire length was shortened linearly. It would not surprise me at all if there were a similar effect occurring in water flow. > hope this helped Yes, I have found all your information helpful. Thank you. Dave
