Author(s): Ling Zhou; Deyou Liu; Huan Wang; Chuanqi Ou; Xuebing Long
Linked Author(s): Ling Zhou
Keywords: Transient flow; Pipe filling; Trapped air; One-dimensional mathematical model; Pressure surge
Abstract: Transient flow of air-water problems in a rapid filling pipeline are simulated by three models. A full water elastic model considers the elasticity of the whole water region, which is solved by using the methods of characteristics (MOC) of rectangular grid. The entrapped air is treated as ideal gas. The first approximation is to neglect the movement of the airwater interface. The second simplification is the application of the rigid water theory for the whole water phase. Comparisons of the calculated and measured pressures are conducted to verify the models. The range of validity associated with two simplifications is also examined. The simplification of constant water length greatly reduces solution complexity avoiding interpolation for moving air-water interface, and the calculation error decreases as the initial air fraction diminishes. The second simplification makes the governing equations simple and the solutions efficient, and avoids the complexity of MOC. The error gradually increases as the initial air pocket volume decreases; especially the results would be undependable when the initial entrapped air pocket is relatively small.
Year: 2015