Quasi-Two-Dimensional Discrete Vapour Cavity Model

In the simulation of transient flow in hydraulic piping systems, vapourous cavitation occurs when the calculated pressure head falls to the liquid vapour pressure head. Rapid valve closure or pump shutdown causes fast transientflow which results in large pressure variations, local cavity formation and distributed cavitation which potentiallycause problems such as pipe failure, hydraulic equipment damage and corrosion. This paper presents a numericalstudy of water hammer with column separation in a simple reservoir-pipeline-valve system. In this study, as a new approach, water hammer with column separation has been modelled in a quasi-two-dimensional form. The governing equations for transient ow in pipes are solved based on the method of characteristics using a quasi-two-dimensionaldiscrete vapour cavity model (quasi-two-dimensional DVCM) and a one-dimensional discrete vapour cavity model(one-dimensional DVCM). It was found that Quasi-two-dimensional DVCM correlates better with the experimental data than one-dimensional DVCM in terms of pressure magnitude. The simulation results clearly show that proper selection of the number of computational reaches and the number of computational grids in radial direction in quasitwo- dimensionalDVCM significantly improves the computational results.

Keywords:

Pipelines , Water hammer , Column separation , Transient cavitating flow , Quasi-two-dimensional discrete vapour cavity model