Analysis And Numerical Simulation Of Small Orifice Leakage In Water Supply Pipeline

The urban water supply pipeline is responsible for transporting water resources.Once the pipe leaks,water will flow out through the leaking orifice,causing a waste of resources and property loss,even endangering public water safety.Under the background of the increasing contradiction between water supply and demand in China,Zhengzhou,a severely water-deficient city,has a high leakage rate of its pipe network.It is found that the total proportion of small orifice leakage is above 80%,on the basis of the pipe leakage data in a water supply area of Zhengzhou during 2011-1014.Therefore,it is necessary to study the leakage of small orifice in its water supply pipeline.This paper mainly studies the influence factors of small orifice leakage and its failure laws under single leakage factor,the aim is to provide theoretical reference for the detection technology,control measure and prediction model of small orifice leakage in Zhengzhou water supply pipeline,and it research the following content:(1)Taking the historical leakage data of a district water supply pipeline in Zhengzhou as a sample,analyzing the main factors affect the leakage of small orifice in pipe.By using the correlation analysis theory in mathematical statistics,the Pearson correlation coefficient between the main factors and the number of small orifice leakage in this area is calculated;(2)Based on the two modules of Computational Fluid Dynamic(FLUENT)and Static Stress Analysis(Static Structure)in ANSYS Workbench platform,the numerical simulation method of unidirectional fluid-solid coupling analysis is accustomed to studying the small orifice leakage in pipe.Firstly,analyzing the flow state and wall stress change after small orifice leakage occurs,then explore the failure law of the small orifice leakage under the leakage factors,pipe materical,pipe diameter,pipe pressure and leakage orifice respectively,based on the method of variable control.According to the main physical quantity in the numerical simulation results,the flow state and the wall stress variation is qualitatively and quantitatively analyzed.By means of the analysis of leakage factors affecting pipe small orifice and the numerical simulation of fluid-solid coupling,get the following results:(1)For the pipe small orifice leakage in a region of Zhengzhou,the overall correlation of pipe material factors is awesome,and the correlation coefficient of pipe diameter factor decreases with the increase of piping diameter.The near-round orifice leakage is the best correlation during the orifice type factor,its correlation coefficient reaches 0.997;(2)In the research range of pipe material factor,as far as the maximum deformation of the leakage hole surface is concrened,the polyethylene material pipe is one order of magnitude higher concrete material pipe,which is two orders of magnitude higher than that of structural steel,stainless steel and grey cast iron pipe;(3)In the research range of pipe pressure factors,the fitting equation of leakage flow and pipe pressure is as follows q=k·H?,and the leakage index is 1.25.The leakage hole deformation increment has a positive linear relationship with the pipe pressure;(4)In the research range of leakage orifice factor,when the leakage ratio(leakage orifice diameter to pipe diameter ratio)is above 4%,the leakage flow has a positive linear relationship with the orifice diameter.When the three common types of leakage have same leakage area,the rank of leakage:flows and maximiums deformation are all as follows:circular hole-shaped leakage>transverse elliptical leakage>longitudinal elliptical leakage.