Identification Of Constitutive Parameters Of Viscoelastic Pipeline Based On Hydraulic Transient Analysis

There are all kinds of pipes in the environment we live in,ranging from urban gas supply pipes to small user water pipes.With the advancement of technology,especially the development of polymer materials technology,the material of the pipeline has also changed,from the original cast iron pipe,stainless steel pipe to plastic pipe.At present,most of the research on hydraulic transients is concentrated on traditional elastic pipes,and the research on viscoelastic pipes like plastic pipes is still in its infancy.Considering the safety problem of the water pipeline during operation,this paper establishes a viscoelastic pipeline transient flow model,transient flow simulation calculation,transient flow experiment and subsequent transient inverse problem analysis.The pressure fluctuations under flow conditions were studied and the parameters of the viscoelastic pipeline were identified.Firstly,from the theoretical point of view,combined with the continuity equation and the equation of motion,the basic differential equation of the pure liquid phase transient flow of the viscoelastic pipeline is derived and the constitutive relation of the viscoelastic pipeline is defined on the basis of this,and the mechanics of the viscoelastic pipeline is established.Model,the mo del used in this paper is the generalized Kelvin-Voigt model;the basic differential equations are solved later,and the finite difference method is used in the solution process;the transient flow simulation model of viscoelastic pipeline is established,and MATLAB is used for programming;Knowing the experimental data is substituted into the program for calculation,and the curve of pressure in the pipeline with time is obtained,and the law is analyzed and compared with the real data,and the feasibility of the model is explained.Then,design and build a test bench.The test bench is in the form of a mixture of elastic pipes and viscoelastic pipes.The main part of the pipe is a stainless steel pipe.The viscoelastic pipes are provided with movable joints at both ends to facilitate the replacement of pipes of different materials,so as to achieve the purpose of the multi-tube experiment;When the viscoelastic pipeline is connected to the elastic pipeline,the natural frequency and transient flow velocity of the pipeline system will change,and the overall performance is viscoelastic;the experimental station is used to conduct transient flow experiments on the HDPE pipe and the MDPE pipe.The variation curve of the pressure in the tube with time is obtained,and the variation law is analyzed and compared with the previous simulation.The rationality of the experimental platform is illustrated,and the basis for the analysis of the constitutive parameters of the viscoelastic pipeline is analyzed.Finally,based on the known viscoelastic pipeline transient flow model and the experimental design data of this paper,the inverse constitutive parameters of the two viscoelastic pipelines in the independent design experiment are identified by the inverse problem analysis method.Taking the least squares method as the theoretical support,The constitutive parameters of viscoelastic pipes are identified by the method of trial calculation,and the error of the identification results is analyzed.In summary,a model of pure liquid phase transient flow in viscoelastic pipes is established in this paper.The viscoelastic pipeline transient flow test rig is built and experimental research is carried out.Based on the system identification theory.The transient inverse problem is analyzed by the parameters of viscoelastic pipeline,which has certain guiding significance for the study of transient flow in viscoelastic pipes.