Investigation of parameters affecting discrete Vapour cavity model

Investigation of parameters affecting discrete Vapour cavity model

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Publishing year : 2014

Conference : National Conference on Civil Engineering, Urban Development and Sustainable Development

Number of pages : 10

Abstract: Rapid valve closure or pump shutdown causes a rapid transitional flow with column separation which causes such problems as hydraulic equipment damage and cavitation. This paper presents a numerical study of a water hammer with column separation in a simple reservoir-pipeline-valve system. The governing equations for two-phase transient flow in the pipes have been solved based on a method of characteristics using a discrete vapor cavity model (DVCM), which has been coupled with four different friction models including Brunone, Zielke, Vardy and Brown, and quasi -steady friction. The DVCM may produce unrealistic pressure pulses (spikes) due to the collapse of multi-cavities. Studies of the DVCM have suggested that using a weighting factor close to 1.0, using the unsteady friction term in the DVCM and restricting the number of reaches to improve computational results, and this paper explores this suggestion in detail. The simulation results clearly show that using the unsteady friction term in the DVCM reduces the unrealistic pressure pulses. It has been observed that using a weighting factor close to 1.0 and restricting the number of reaches does not improve the computational results in all cases. Instead, the proper selection of these parameters reduces the unrealistic pressure pulses.