Analysis Of Strain Delay Response Characteristics Of Transient Flow In Viscoelastic Pressure Pipe

Pipelines play a vital role in urban life,and the stable operation of pipeline systems is a key factor to ensure the orderly production and life in cities.Whether it is overseas where the research on pipeline started earlier or domestic where the research on pipeline is developing rapidly,scholars for the prevention of pipeline hazards have started from the study of elastic pipeline.With the development of polymer materials,more and more viscoelastic pipes are used in water transmission projects,and the research direction of pipeline system protection is gradually shifted to viscoelastic pipes.When transient flow occurs in the pipeline,the strain of elastic pipeline occurs almost simultaneously with the stress,while the strain of viscoelastic pipeline always lags behind the time of stress,which is called the strain delay response characteristic of viscoelastic pipeline.In order to study this characteristic more accurately,this paper establishes a strain-delayed response model for viscoelastic pressurized pipes with transient flow,and verifies the accuracy of the model with experiments,and finally tests the practicality of the model with engineering examples.First,the generalized Kelvin-Voigt model is chosen to simulate the mechanical properties of viscoelastic pipes by analyzing the intrinsic structure relationship of viscoelastic pipes;the differential equations for transient flow of viscoelastic pressurized pipes are derived,and the compatibility equations are obtained by solving with the characteristic line method,and the delayed response model for transient flow of viscoelastic pressurized pipes is established;the basic data are substituted into the model program,and the delayed response model for transient flow of viscoelastic pressurized pipes is obtained by MATLAB software.The numerical calculation is carried out to obtain the numerical simulation results of the transient flow in the viscoelastic pressurized pipeline,and the simulation results are analyzed to obtain the maximum pressure value in the pipeline during the transient flow related to the pressure and flow rate at the initial moment.Secondly,the existing hydraulic transient experimental bench was improved,and the experimental content was designed with the numerical calculation conditions,and replaceable pipe sections were set up for replacing different types of pipes for experimental studies.The pressure variation of four different pipes with time when the transient flow occurs is experimentally obtained,and the strain delay response characteristics of viscoelastic pipes are verified;the numerical calculation results are compared with the experimental results,and the maximum relative error value between the simulated and experimental values is mainly around 6%;after analyzing the difference between the model data and the experimental data,it is concluded that the reason for the error is mainly due to the difference between the simulated pipe and the experimental The differences between the model and experimental data were analyzed and it was concluded that the errors were mainly due to the differences between the simulated and experimental pipes and the presence of transient friction in the pipes.Finally,this paper applies the delayed response model of transient flow strain in a viscoelastic pressurized pipe to an engineering example.The research content in the case was clarified according to the case background,and the model was adjusted according to the needs of the engineering case.Subsequently,after numerical calculations,the PE pipe in the case was obtained to meet the actual needs of the engineering,and the results also verified the strain-delayed response characteristics of the viscoelastic pressurized pipe.In summary,this paper analyzes the strain-delayed response characteristics of viscoelastic pressurized pipe transient flow,introduces the pressure changes of different pipes when transient flow excitation occurs,clarifies the strain hysteresis phenomenon of viscoelastic pressurized pipe and the law of energy consumption in the pipe,and provides a basis for establishing effective water hammer protection measures,followed by practical examples to illustrate the engineering applicability of the proposed model and prove its value in practical engineering.The application value of the model in practical engineering is proved.