Yixing Yuan

A diameter‐sensitive flow entropy method for reliability consideration in water distribution system design

Flow entropy is a measure of uniformity of pipe flows in water distribution systems. By maximizing flow entropy one can identify reliable layouts or connectivity in networks. In order to overcome the disadvantage of the common definition of flow entropy that does not consider the impact of pipe diameter on reliability, an extended definition of flow entropy, termed as diameter-sensitive flow entropy, is proposed. This new methodology is then assessed by using other reliability methods, including Monte Carlo Simulation, a pipe failure probability model, and a surrogate measure (resilience index) integrated with water demand and pipe failure uncertainty. The reliability assessment is based on a sample of WDS designs derived from an optimization process for each of the two benchmark networks. Correlation analysis is used to evaluate quantitatively the relationship between entropy and reliability. To ensure reliability, a comparative analysis between the flow entropy and the new method is conducted. The results demonstrate that the diameter-sensitive flow entropy shows consistently much stronger correlation with the three reliability measures than simple flow entropy. Therefore, the new flow entropy method can be taken as a better surrogate measure for reliability and could be potentially integrated into the optimal design problem of WDSs. Sensitivity analysis results show that the velocity parameters used in the new flow entropy has no significant impact on the relationship between diameter-sensitive flow entropy and reliability.

Water distribution network real-time simulation based on SCADA system using OPC communication

Hydraulic simulation models of water distribution networks (WDN) are routinely used for operational investigations and network design purposes. However, their full potential is often never realized because in the majority of cases, they have been calibrated with data collected manually from the field during a single historic time period and reflects the network operational conditions that were prevalent at that time. They were then applied as part of a reactive investigation. An urban water distribution network real time simulation system based on SCADA system using OPC (object linking and Embedding(OLE) for Process control) communication was built in this paper. In order to make real-time simulation of water distribution network, the real-time data was collected every 15 minutes, the real time data were received and sent into water distribution network simulation model by OPC communication of SCADA system. The real-time data included total head of reservoir, flow rate, pressure, pump operation information. The real-time simulation system can give timely warning of changes for normal network operation, providing capacity to minimize customer impact and comparing the simulation results with the real-time data collected. The real time simulation system of urban water distribution network solved the problem of data input and user interaction compare to traditional network model. It offers a way for the development of intelligent water network.

RESEARCH ON WATER DISTRIBUTION NETWORK CALIBRATION USING HEURISTICS ALGORITHM AND PIPELINE RESISTANCE COEFFICIENT EMPIRICAL MODEL

The water network was calibrated by two steps. The nodal demand was calibrated firstly, and then the pipeline resistance coefficient was calibrated. The results of steady state, fire flow state and expended period simulation were selected for model calibration. The tank level and the pump station flow were selected as the calibration object. For fire flow state, the node demand and nodal pressure were used. For the first step, the pipeline resistance coefficient calculated by empirical model which was built on the basis of large number of field test data for all kinds of pipes, and equivalent flow rate was introduced in order to accelerate nodal demand calibration. After then, pipeline resistance coefficient was calibrated at the base of nodal demand calibrating result and the requirement of objective function converging was more higher than the first step. The heuristics algorithm was applied on water network calibration.

The water distribution network digital management platform in Harbin, China

Water distribution network rehabilitation project is based on the digital analysis platform. The platform is built on the basis of microscope model in water distribution network. The water distribution network can be simulated under all kinds of scenarios, and the state-of-art can be shown in many ways by the digital analysis platform. It is very useful for the switch between the new and the old water sources, and for optimal control of water network. The digital analysis system for water distribution network has been successfully applied in the switch of water sources in a metropolis in north-eastern China. In conclusion, the digital platform is a powerful tool to realize the digital water distribution network. And it also provides effective guarantee for scientific control, operation, management and improvement of water distribution network.

Optimization of Monitoring Point Placement of Water Quality in the Water Distribution System Based on TEVA-SPOT

With the global escalation of terrorist attacks, water supply network has become the weak links exposed to terrorists. Many countries have already raised infrastructure security as homeland security strategies, developing a corresponding tool to simulation and analysis vulnerability for the water distribution system (WDS). This paper is aiming at the non-source pollution in the WDS, and the water quality monitoring points are established. According to the theory of tracing exogenous pollutants in water distribution network, the model is developed by TEVA-SPOT optimizing monitoring point placement of water quality. This study is working to reduce system vulnerabilities, prevent and prepare for terrorist attacks, minimize public health impacts and infrastructure damage, and enhance recovery.

Analysis of Water Supply Capacity under the Condition of Trenchless Rehabilitation Technology

The trenchless technology has been widely used in water pipeline recovering technology, in which various kinds of pipes are used. This paper discussed the appropriate supply hydraulic calculation method for respective pipes through analysis of flow pattern in the pipes. Then their respective water supply capacities are analyzed qualitatively and quantitatively, which can provide references for designers, managers, construction workers.

Study of Mixing at Cross Junction in Water Distribution Systems Based on Computational Fluid Dynamics

Solute mixing at the cross junction was assumed to be instantaneous and completely mixed in initial water quality models of water distribution system. With recent developments, some computational simulations and experiments verified an incomplete mixing state at cross junctions, which affected the accuracy of water quality model in water distribution networks. This paper, by the theory of computational fluid dynamics, confirms incomplete mixing at the pipe intersections. At the cross of pipe network, the forward direction of the fluid particle is directly related to water momentum. A mixing model at the cross in water supply networks is established to improve the water quality model and the simulation accuracy. For the potential of accidental or intentional contamination events, it makes a powerful prediction. This study is working to prevent and prepare for terrorist attacks, minimize public health impacts and infrastructure damage, and enhance recovery.

Research on Water Quality Comprehensive Evaluation Index for Water Supply Network Using SOM

A water quality comprehensive evaluation was taken for the water in water supply network. It was on the basis of water supply network microcosmic model. The water quality indicators, by which the state of water quality was expressed, were chosen as the input vector for the comprehensive evaluation model. The self-organizing feature map and k-means arithmetic were taken in the model. As a result, a comprehensive water quality evaluation method was proposed for the defects of single indicator grade evaluation. And the objective water quality evaluation model of water supply water network was taken. Compared with the single-evaluation indicators, SOM can take into account the single water quality monitoring data and the overall data, and reflect the water quality distributing in the water supply network objectively.

Urban Daily Water Demand Short-Term Forecasts Based on the Chaos Theory

The characteristics of the chaos theory are analyzed in this paper. The urban daily water demand short-term forecasts model, which is for the scientific forecast of the urban daily water demand, is built based on the chaos theory. The time-series of urban daily water demand is analyzed on the basis of phase space reconstruction and the historical data of water demand is used. The saturated embedding dimension, delay time and Lyapunov exponent were solved. And they are used in urban water demand forecast. The urban daily water demand was taken by the forecasting model in a large city in the northeast china. As a result, the urban daily water demand short-term forecast model, which is affected by many factors, has a high precision and a good value.

WATER DISTRIBUTION NETWORK RESIDUAL CHLORINE MODELING BASED ON THE SYNERGY OF CHLORINE AND CHLORINE DIOXIDE

The kinetics and mechanisms of chlorine dioxide and chlorine in water distribution network is described, and a multi-species network water quality model is built in this paper. Experiment was composed of two parts, static test and dynamic test. The cast iron pipe, steel pipe, and PVC pipe were selected to carry out static experiments. In order to study the kinetic and mechanism of the combination disinfection of chlorine dioxide and chlorine, the reaction was under the condition of different chlorine dioxide and chlorine dosing ratio and different chlorination method. Dynamic experiments carried out in the cast iron pipe in different chlorine dioxide and chlorine dosing ratio and different flow conditions to study the kinetic and mechanism of the combination disinfection of chlorine dioxide and chlorine .A multi-species network water quality model using EPANET-MSX toolkit is built based on kinetic and mechanism of the combination disinfection of chlorine dioxide and chlorine. The concentration of residual chlorine (Cl2), chlorine dioxide (ClO2), chlorite in the bulk water and biofilm was taken as the main parameters. And the model was calibrated by the experiment data. The water quality model application in a large water distribution network, of which the total demand is 800,000 m 3 /d in China. The results show that the combination of chlorine dioxide and chlorine disinfection can reduce the chlorine and chlorine dioxide disinfection by-product and residual chlorine concentration distribution was more reasonable.