Unsteady vortices in the test pump sump with 100 mm height and 100 mm diameter of the inlet pipe are investigated by performing large eddy simulations (LES). Computational grids composed of 2 billion hexahedral elements with 0.255 mm resolution were used for the LES. These grids resolve the turbulent boundary layer that develops on the wall of approaching channel; however it is not enough fine to capture viscous core of the submerged and air-entrained vortices. In this study, we focused to analyze how and why submerged and air-entrained vortices were appeared and disappeared. By performing LES for a long time period (～16 seconds), we successfully captured the unsteady events several times, including generations and disappearances of the submerged and air-entrained vortices. In this paper, the details of the appearances and disappearances of vortices will be shown.
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