Simulation of an air cushion inverted siphon

The article considers the problem of silting-up of sewage inverted siphons. A review of modern methods of hydraulic flushing is presented. To ensure reliable and energy-efficient operation of the inverted siphon, it is proposed to use the air cushion effect. To ensure the stable operation of the structure, a simulation of the inverted siphon installation was performed, consisting of two sections with nodes for receiving runoff from the drop risers, a node that provides water removal and a node for regulating the pressure in the air cushion. As a result of the simulation, there has been obtained the distribution of the volume fraction of the water phase and the gas phase, the pressure distribution in the horizontal and vertical inverted siphon pipelines and the values of the flow velocity during the formation of the air cushion. The use of separation partition walls at the ends of horizontal siphon pipelines allows creating autonomous air cushions and regulating the work for each section separately. The adaptation of the air cushion inverted siphon technology in relation to the main sewer system is considered to be promising.

Application of Model Predictive Control for Large-Scale Inverted Siphon in Water Distribution System in the Case of Emergency Operation

The emergency control of Menglou~Qifang inverted siphon, which is about 72 km long, is the key to the safety of the Northern Hubei Water Transfer Project. Given the complicated layout of this project, traditional emergency control method has been challenged with the fast hydraulic transient characteristics of pressurized flow. This paper describes the application of model predictive control (MPC), a popular automatic control algorithm advanced in explicitly accounting for various constraints and optimizing control operation, in emergency condition. For the fast prediction to the pipe-canal combination system, a linear model for large-scale inverted siphon proposed by the latest research and the integrator-delay (ID) model for open canals are used. Simulation results show that the proposed MPC algorithm has promising performance on guaranteeing the safety of the project when there are sudden flow obstruction incidents of varying degrees downstream. Compared with control groups, the peak pressure can be reduced by 17.2 m by MPC under the most critical scenario, albeit with more complicated gates operations and more water release (up to 9.75 × 104 m3). Based on the linear model for long inverted siphon, this work highlights the applicability of MPC in the emergency control of large-scale pipe-canal combination system.

Linear model of water movements for large-scale inverted siphon in water distribution system

This paper proposes a linear model that relates the pressure head variations at the downstream end of an inverted siphon to the flow rate variations at two ends. It divides the pressure head variations in the inverted siphon into low-frequency part and high-frequency part. The two parts are caused by the deformation of the siphon wall and the reflection of acoustic wave, respectively. In order to build a simplified relation between wall deformation and low-frequency pressure head variations, the Preissmann slot method (PSM) is adopted in this paper. The linear model can also be used in other forms of structures, such as pipes and tunnels, where a pressurized flow condition is present. In comparison with simulation results using the finite volume method, the linear model shows an L2 norm of 0.177 for a large-scale inverted siphon and 0.044 for a PVC pipe. To this end, the linear model is adopted to model a large-scale inverted siphon in a virtual water delivery system. Simulation results show that the inverted siphon can reduce water fluctuations. An equation to quantify this effect is proposed based on the linear model.