Transient Pressure Analysis Of Viscoelastic Pipe Based On Quasi-2D Model

Pressure pipes are an important part of the urban municipal system.In recent years,with the improvement of pipeline production equipment and production processes,the materials of pressure pipes have become more and more diverse.Among them,the application of plastic pipes with viscoelastic mechanical properties has become more and more common.However,the hydraulic dynamic characteristics of viscoelastic pipes are more complicated than traditional elastic pipes.Therefore,based on the pipeline transient flow theory,this paper studies the pressure fluctuation and energy loss of the transient flow of the viscoelastic pipeline.The main research contents are as follows:Firstly,the constitutive model based on viscoelastic pipeline is combined with one-dimensional quasi-steady-state friction model,unsteady-state friction model and quasi-two-dimensional model to establish one-dimensional viscoelastic pipeline transient flow model and quasi-two-dimensional viscoelastic model Pipeline transient flow model.The simulation results of three different friction models of the viscoelastic pipeline transient flow model are compared with the experimental results in the literature to analyze the advantages and disadvantages of the different models.It was found that compared with the one-dimensional viscoelastic pipeline transient flow model,the quasi two-dimensional model has a higher degree of fitting to the experimental values in terms of pressure peaks,valleys and pressure wave periods,and can accurately simulate viscoelastic pipelines.The pressure fluctuation process of transient flow.Secondly,this paper makes a nuclear examination of the pipeline creep parameters and pressure wave velocity in the viscoelastic pipeline transient flow model.Based on the creep function measured in the mechanical experiments provided in the literature,the number of elements of the creep parameters in the model under different experimental conditions is evaluated by genetic algorithm from 1 to 5.At the same time,the wave velocity calculation method of three different tubes is used to calculate the wave velocity in the model,and then the wave velocity value and the creep parameters obtained by the proposed auditor are combined into the quasi-two-dimensional viscous elastic pipeline transient flow model,and the wave velocity value in the model is determined based on the comparison of the simulation results with the experimental data.Then,the creep element number from 1 to 5corresponding creep parameter value and wave speed value into the model,analysisof different parameters under the simulation results and experimental data fit degree,compared the optimal simulation results for the model of the number of creep elements of 3.Finally,combined with the energy expression of pipeline fluid compression,the energy equation of the one-dimensional and quasi-two-dimensional viscous elastic pipeline transient flow model is established,and the ratio of pipe delay strain in total strain to the total strain in different fluid temperature and initial Reynolds number,the energy change caused by the pipeline’s original structure characteristics,and the influence of the energy loss and pressure fluctuation caused by the pipeline resistance.The results show that with the increase of fluid temperature,the proportion of delayed strain caused by the viscous elasticity of the pipe increases in the total strain,the energy change caused by the pipe’s structure characteristics increases compared with the energy change power caused by the pipeline resistance,but the ratio of the former in the sum of the two shows an upward trend,in addition,the peak of the transient pressure wave decreases with the increase of the fluid temperature and the fluctuation frequency decreases gradually.With the increase in the number of renoms of fluid in the pipe,there was no significant change in the ratio of delay edgitude to total strain and the ratio of the work done by the pipe stickelasticity to the work done by the pipe resistance,except for the increase in the peak during each cycle of the transient-flow pressure wave.It is concluded that the role of the viscous elasticity of the pipe in pressure attenuation increases with the increase of fluid temperature,but it has no obvious relationship with the size of the steady-state Reynolds number.