Using DGCM to predict transient flow in plastic pipe

Abstract

Transient flows with cavitation are commonly existent and observed in pressurized conveyance systems. The occurrence of large cavitation caverns accompanying hydraulic impacts in the pressurized pipes is particularly dangerous. There may then be interference of pressure waves traveling inside the pipe (especially between initial and secondary pressure waves). The maximum instantaneous pressures can rise in the most dangerous scenario to-magnitude that are twice as large as those calculated with a classic formula of Joukowsky. To protect these systems at the design stage it is advisable to estimate large pressure pulsations using appropriate numerical models. In this work transient cavitating flow in the plastic pipe was modeled using the modified discrete gas cavity model (DGCM). Retarded strain occurring in the studied plastic pipe was modeled with the aid of a convolutional integral of stress history and a derivative of the creep compliance function of the plastic pipe wall. In the simulation, the unsteady wall shear stress was determined using the recent Urbanowicz's computationally effective method.