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The classical Discrete Vapour Cavity Model (DVCM) is widely used in standard water hammer software packages. Column separation in pipelines is usually predicted with this model. Nevertheless, its main weakness consists in the numerical instability and non-convergence. This paper deals with the investigation of the coupled DVCM obtained by incorporating the classical DVCM into the FSI-water hammer model. Transient is caused by a fast-downstream valve closure in a quasi-rigid straight pipe. Pressure at the fixed valve is predicted by considering only friction and Poisson coupling. The method of characteristics (MOC) with wave-speed adjustment scheme is used in calculation. The staggered grid is used for the first time to solve the coupled DVCM, and the simulation clearly shows its preference to the rectangular grid. To validate the proposed model, the numerical results are compared against experimental data from the literature. Moreover, damping effect of unsteady friction losses improves the numerical solution. In addition, the variable wave-speed method allows more accuracy in the lesser computation time. Therefore, accuracy, stability and convergence of the numerical solution may lead to incorporate the new model into commercial codes. |
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