Computational fluid dynamics simulations are carried out to characterize the spatial and temporal characteristics of the velocity and pressure field of turbulent flows through a pumpturbine unit operating with the turbine mode. The high-fidelity large eddy simulations turbulence model is utilized to examine the flow-induced vibrations in the draft tube of the unit. The water injection from the runner cone is considered as the control strategy to mitigate the flow-induced fluctuations. The simulations are conducted for the turbine flow rate of 0.2 m3/s without and with the water injection at a rate of 0.008 m3/s. The pressure along the surface of the draft tube is probed at various locations to access the effectiveness of the water injection to mitigate fluctuations. Water injection at 4% rate is demonstrated to be effective in attenuating the pressure fluctuation inside the draft tube. The amplitude of fluctuations is reduced by nearly 50% by the water injection. The generated power is hardly influenced by water injection. Thus, the control strategy considered here could be employed effectively without a penalty on the power generation.

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