Siphon outlets of pump discharge lines are used in pumping plants. It is necessary to evacuate air downstream from siphon outlets as bubble entrainment by water flow after plant start-up. A numerical method has been developed for prediction of gas-liquid two-phase flow dynamics during self-priming of the siphon outlets by using a two-dimensional extended two-fluid model. This method is appropriate for the present purpose because it can treat free surface of water layer on inclined wall and entrained bubbly mixture in a water pool, both of which occur in siphon outlets. Experiments were carried out by using a 1/15 scale test-section. The calculated results of transient water level and pressures in the simulated siphon outlets were in good agreement with the experimental data. The results reveal that the present method can predict key hydrodynamic phenomena in siphon self-priming process and the present method is a useful tool for design of actual large-scale siphon outlets.
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