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A siphon (; also spelled syphon) is any of a wide variety of devices that involve the flow of liquids through tubes. In a narrower sense, the word refers particularly to a tube in an inverted "U" shape, which causes a liquid to flow upward, above the surface of a reservoir, with no pump, but powered by the fall of the liquid as it flows down the tube under the pull of gravity, then discharging at a level lower than the surface of the reservoir from which it came. There are two leading theories about how siphons cause liquid to flow uphill, against gravity, without being pumped, and powered only by gravity. The traditional theory for centuries was that gravity pulling the liquid down on the exit side of the siphon resulted in reduced pressure at the top of the siphon. Then atmospheric pressure was able to push the liquid from the upper reservoir, up into the reduced pressure at the top of the siphon, like in a barometer or drinking straw, and then over.

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Experimental study at prototype scale of a self-priming free surface siphon

Giovanni De Cesare, Paloma Furlan

This study is within the frame of the construction of the rail link between Geneva Cornavin station, Eaux-Vives station and Annemasse (CEVA). The project area is located at a cut-and-cover tunnel built by slurry walls located in the alluvium of the Foron River. The installation of the covered trench cuts the groundwater table flow, which causes a rise of the water table in spite of the partial evacuation by the Foron. It is therefore planned to add about thirty wells in order to transit the waters of the aquifer from one side of the tunnel to the other. A thorough reflection allowed to find an alternative solution to traditional pumping consisting of putting in place self-priming multiphase siphons which forms the basis of the following study. The operating principle of the system is based on the maintenance of a free-surface vortex in a vacuum in what will be called the sealed box which functions by keeping the siphon primed to allow water to be transferred from either side of the gallery. This study explores the performance of a physical model of the system with the following objectives: (1) To characterize the initiation and stability conditions of the system by maintaining the vacuum in the sealed box and (2) to characterize the limiting operating conditions of the system in relation to the ground water table levels which relates to insufficient air entrainment due to low outflow or submergence of the sealed box. The experimental installation is fabricated at a scale of 1:1 so as not to introduce scale effects by the presence of air, the water-air mixture and the free-surface vortex in a vacuum atmosphere.

2017

Experimental Study at Prototype Scale of a Self-priming Free-Surface Siphon

Giovanni De Cesare, Paloma Furlan

Springer2018

Vortex siphon - from 1:1 scale physical model to SPH simulation and prototype

Giovanni De Cesare

The rail link between Geneva Cornavin Station, Eaux-Vives Station and Annemasse (CEVA) is currently under construction including a cut-and-cover tunnel built by slurry walls located in the alluvium of the Foron River. The covered trench cuts the groundwater table flow which causes a rise of the water table on one side of the tunnel. Thirty wells were built in order to convey water from the aquifer on one side of the tunnel to the other. For each well, traditional pumping has been replaced by a self-priming multiphase siphon in order to lower energy costs. The operating principle of the system is based on the sustaining of a free-surface vortex flow in a vacuum chamber. In this way, the multiphase siphon is primed to allow water to be transferred from either side of the tunnel. A physical model of the conveyance system has been constructed at a scale of 1:1 in order to avoid scale effects from the presence of air water mixture and due to the free-surface vortices sensitivity to scaling, particularly in a vacuum atmosphere. In this study, the results from the physical model are used to validate a Smoothed Particle Hydrodynamics (SPH) numerical simulation of the complex flow conditions. The DualSPHysics code is employed and the results presented herein regarding the depth discharge relationship are encouraging for further application in vortex flows and such devices where conventional Eulerian modelling approaches can be challenging. As far as the authors are aware, this is the first application of SPH in simulating vortex chamber flows and the result bodes well for further application in this area.

2019

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