NUMERICAL MODELLING OF TRANSIENT LAMINAR FLOW IN A POLYMER PIPE

Polymer pipes exhibit both elastic and viscoelastic properties differentiating them from purely elastic pipes. It is well known that their mechanical properties, especially, creep function and relaxation time, are strongly influenced by the variation of temperature. The  main aim of the present work is devoted to a mixed method for analyzing hydraulic transient laminar flow in a polymer pipe such as polyethylene by taking into account viscoelasticity of constituent material of pipe and the variation of temperature. The instantaneous shear stress is determined using polynomial expansion of instantaneous velocity profiles of the flow in radial variable through the pipe section. The average pressure and average velocity of the fluid flow are obtained by the method of characteristics. This numerical approach has the advantage, compared to the Zielke model, of bypassing the calculation of the convolution product. The comparison of the results obtained in elastic pipe with experimental results of Holmboe allows to confirm the validity of the present model. Further, an extension to a polymer pipe with linear viscoelasticity is carried out by taking into account the variation of temperature. Received: June 15, 2024Revised: July 18, 2024Accepted: July 30, 2024