| Urban water distribution systems (WDS) are the critical infrastructures in city, which are responsible for delivering water to users all over the city uninterruptedly. Any failure that causes the users to fail to receive sufficient pressure and flow rate will have an enormous disaster impact on normal life and productive activities of the people. The research and improvement of reliability for WDS has positive realistic significance for ensuring daily water demand of users effectively and increasing the economic and social benefits of water utility. In this paper, water distribution systems reliability is mainly studied based on its physical model. And then the feasibility of surplus power entropy (SPE) being used as a reliability indicator, influencing factors and assessment methods of WDS reliability under various abnormal conditions are also studied to provide guidance for the design, operation, diagnosis and maintenance of a WDS.Firstly, the structure of user node in physical model is designed as “pressure meter–ball valve” pattern in order to simulate the water demand of user node. The Hazen-Williams coefficient C of pipe is simulated by controlling the opening of ball valve situated at corresponding pipe. By comparing the operating results between physical model and its simulation model by EPANET, the results indicates that the physical model experiment can simulate the hydraulic conditions of WDS effectively. And its experiment results can meet accuracy requirements of reliability experiment in this paper.Secondly, considering that the WDS with higher redundancy structure and equivalent surplus power factor among upper pipes has higher reliability under failure conditions (such as increasing water demand and pipe failures, etc.), surplus power entropy is introduced to describe the uniformity of surplus power factor among the upper pipes. While the surplus power factor describes the surplus water supply capability of pipe, entropy measures the uniformity of element distribution among upper pipes. An effective experimental study on SPE being as a reliability indicator is conducted by physical model experiment. A comparison between SPE and some classical reliability indicators is done by acquiring some related operating data and calculating these indicators under a range of failure conditions. These classical indicators include available water reliability, pressure reliability, flow entropy, resilience index and surplus power factor. The comparison results show a positive relationship between SPE and other reliability indicators, which confirms the feasibility of SPE being used as an indicator of capacity reliability.Thirdly, low reliability caused by increasing water demand and optimization scheduling after isolating the bursting pipe are studied based on physical model experiment from the viewpoint of improving reliability and reducing energy consumption. And then，the dividing district model based on node elevations and the multi-objective optimal scheduling model taken pump operation frequencies as decision variables are established and confirmed by physical model experiment. Finally, water distribution system reliability assessment model is establishedbased on “bursting area-consequences” pattern. This model takes the stochastic bursting of pipe as uncertainty factor sources and can reflect the reliability of WDS correctly because of considering some factors, such as the availability of pipe, variable water demand of users during a hydraulic operating cycle, layout of valve and optimization scheduling. In the bursting experiment, due to the infeasibility of enumerating failing pipe and their combinations one by one, a regional division method is proposed, based on the layout of valves. WDS is assessed after every district is isolated from the WDS one by one. This method greatly reduces the number of experiment. |
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