automatic bell siphon

A closed hydraulic circuit showing how an automatic bell siphon works. 

The bell siphon's working principle is the same as that of the so-called  Pythagorean cup. Only wise drinkers could taste wine in this cup, while greedy ones who filled the cup beyond the prescribed level would see it drained through the siphon. Hence, the cup is also known as a greedy cup. 

The experimental set-up is a modified version of the one presented at the AGU Fall meeting 2016 https://www.youtube.com/watch?v=71E52Mbj32s&t=48s

Blu and yellow colors are chosen as a tribute to Ukraine's population facing the nightmare of an absurd war.

An automatic bell siphon is placed in the upper tank, and is fed by a small submersible pump in the bottom tank on the right. 

When the siphon is activated the water flows in the bottom tank on the left and fills it

The two bottom tanks are connected through the holes in the vertical wall. 


Filling and emptying of the siphon. The depression inside the bell is witnessed by the higher water level. Discharge is guaranteed until the outer water level reaches the bottom part of the bell walls and enters the bell. 

Slow-motion view of the bottom part of the hydraulic circuit. 

The moment when an air bubble enters the siphon. Few instants later the flow from the siphon stops. 

A snapshot showing the different trajectories due to the different hydraulic head. Trajectories are not continuous due to the air inclusion in the tank caused by the incoming jet from the siphon. 

The bottom part of the set-up resembles the experiment described by Leonardo da Vinci.