Abstract
The immersed boundary lattice Boltzmann method (IB-LBM) was applied to numerically simulate the runaway process of tubular turbines with the influence of the free surface of upper and lower reservoirs. First, the accuracy of the IB-LBM method was verified, and then the external performance and internal flow characteristics of units during runaway process were studied. The results show that the gravity causes uneven pressure distribution at inlet of the turbine with considering the influence of the free surface of the reservoirs, resulting in complicated flow pattern, which cannot be ignored in the study. In the course of runaway, low-pressure area of draft tube changes periodically with a certain degree of cavitation occurring on pressure and suction surface of the blades, which threatens the overall operation stability of the unit.
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