Hacker News Reader

Comment by zeristor | Hacker News Reader

I am particularly amazed by the water vortex drawing in air to enable the water to rise higher.

I'm not sure i believe that bit. If you can lift a flow of water from one level to a higher level without an input of energy, you have a perpetual motion machine. And those aren't allowed.

I assume that what happened here is that some fraction of the input flow was drained to a lower level, and the liberated potential energy captured and used to lift the remaining fraction to a higher level. That's not what's shown in the video, though.

There's a description starting on page 369 here, although it's not completely clear how it works (the author is an archaeologist, not an engineer!): https://sci-hub.se/10.1093/jis/etw016

Subsequent prior art (IYSWIM) is the hydraulic ram, which does this a different way: https://en.wikipedia.org/wiki/Hydraulic_ram

In the pdf you provided a significant portion of the water appears to drain. So the energy equation might work out.

Indeed. Fascinating puzzle. Without an external source of energy there must be a volume of water leaving the system that doesn't make it to the higher level. If it was possible to partition the water and the energy but not with the same partition (ie, 40% of the water gets 80% of the energy, 60% of the water the other 20%) then the system would be thermodynamically legal. So maybe the vortex was to create a high- and low- pressure mass of water.

This mechanism is ingenious in the best meaning of the word.

I wonder if the extra energy is the kinetic energy (the water rushes into the cistern to create the vortex, but then is still when it's raised).

The first video I saw was a YouTube short purely on this, I had thought it was just taken from this main video.

My understanding was that the water was aerated, and so less dense meaning it could rise higher.

Værsgo:

https://youtube.com/shorts/BkVUQQnfrDg

Ideally I’d like to see an experiment to explicitly confirm it.

The vortex might be a variation of a trompe, a water-powered air compressor. The compressed air is in turn used as an airlift pump.

new to me: https://en.wikipedia.org/wiki/Trompe

https://en.wikipedia.org/wiki/Airlift_pump

edit: the text version of the video refers a study that I don't have access to.

https://primalnebula.com/the-engineering-of-the-alhambras-wa...

The Mastery in Hydraulic Techniques for Water Supply at the Alhambra García-Pulido, Luis José Journal of Islamic Studies, Volume 27 (3) – Sep 1, 2016 https://www.deepdyve.com/lp/oxford-university-press/the-mast...

Yep, saw this video a while ago and came here to say that there’s multiple clever systems in place, but that bit’s definitely worth a watch. It’s at about ~7:30

Reply on news.ycombinator.com