Simulation of unsteady flow in viscoelastic pipes

The paper focuses on modeling of unsteady flows in a hydraulic system built of a pressure tank, a plastic pipeline and a quick-closing valve. The influence of unsteady friction as well as the experimentally obtained creep function (necessary for modeling retarded strains) on simulation results was investigated. In addition, the effectiveness of the dimensionless parameter P known from the literature was analyzed, especially in the context of rejecting an unsteady term decision. Detailed investigations on the variability of terms describing unsteady friction have shown that one should still look for a dimensionless parameter with the help of which it will be possible to decide on the friction model before making the calculations. The quantitative analysis carried out showed that the use of unsteady hydraulic resistance in simulated runs brought simulated results closer to experimental results.