New modelling of column separation in pipelines with fluid-structure interaction and gas release

The efficiency of cavitation models depends on physical and dynamic parameters affecting the cavitating flow. The discrete gas cavity model (DGCM) is an efficient alternative to the discrete vapour cavity model (DVCM) in prediction of column separation in pipelines. However, pipe vibration and structural loading cannot be predicted with it. This paper deals with investigation of the coupled DGCM obtained by incorporating the classical DGCM into the governing equations of the water hammer four-equation model. The numerical procedure and the selective criterion established for the solution are novel. The pressure at specific locations of an elastic straight pipeline is predicted by use of the method of characteristics (MOC) with wave-speed adjustment (WSA) scheme. Several parameters affecting the result are investigated, but special emphasis is made on the constraint condition of the pipe. The model is validated against experimental results from the literature by performing both time and frequency analysis. The good agreement observed can allow the proposed model to be incorporated into commercial codes.