Research And Simulation Of Blockage In Water-Supply Pipelines Based On Fluid Oscillation Theory

With the increment of service time, blockage appears inevitably in the water-supply pipelines. The blockage not only influences the normal working state of pipelines, reduces the system's operating efficiency, but also destructs the supplying water quality which will hazard people's health. Simultaneously, the pressure in pipelines will rise because of a blockage. Once the pressure in pipelines exceeds the load which the pipelines could bear, a leakage will generate, even a squibbing. It not only brings the loss of the water resources, but also severely threats the safety of people's life and property. Consequently, it has important signification to research the blockage detection in pipelines.In this paper, according to the design feature of water-supply pipelines, the simplified model is put forward for the numerical simulation of blockage detection based on fluid oscillation theory. Two kinds of blockage are discussed in this paper. One is a certain length blockage generated by microbial propagating largely and chemical corrosion or precipitation, the other is a blockage because of the valve's partly opening. Forced oscillations and auto-oscillations are used to be excitation respectively. By analyzing the response characteristics of pipeline system, the blockage in the pipe line can be detected, located and quantified.In this paper, the hydraulic impedance method based on forced oscillations is used for detecting blockage with a certain length. When the boundary condition is a periodic disturbance flow rate, blockage is detected by analyzing the amplitude of fluctuating pressure at the measuring point varying with the frequency of disturbance flow rate. In single pipeline systems a formula is concluded to determine the blockage location. And the validity and applicability of the formula is verified by changing the length and diameter of the pipeline. When the blockage location is fixed, the blockage magnitude can be determined according to the difference between the peak and the hollow of the frequency response diagram describing the relative value of fluctuating pressure peak. Program implemented with Fortran is used to simulate various conditions in water-supply pipelines numerically such as different blockage location and magnitude.Governing equations for transients in a pipeline including the opening state of valves are established with the adoption of Dirac delta function in the auto-oscillations method. An analytical solution expressed in terms of a Fourier series has been developed under fixed boundary conditions. By Fourier series analyzing the analytical solution, the amplitudes of each harmonic component in different periods is calculated. Then the damping exponent of each harmonic component can be obtained. The location and opening state of the valve can be fixed if two valve blockage damping parameters are known. The location and opening state of the valve is simulated numerically with C++ program.In this paper, fluid transient theory and oscillation theory have been associated to analyze the fluid oscillation in hydraulic system. The method has high accuracy in determining the blockage location and magnitude in water-supply pipelines, furthermore short calculation time. Therefore, this method has reference function for blockage detection in practical water-supply pipelines.