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3-D unsteady turbulent flow simulation with RNG k—ε turbulence model of complete flow passage on Francis turbine at partial load condition was performed. The simulation results were compared with the test data. The simulation predicted the pressure fluctuation magnitude and frequency characteristic in the draft tube successfully. A method injecting water from the crown tip to the turbine draft tube to weaken the pressure fluctuation was introduced. Simulation of the flow with water jet was performed, showing that the water jet weakened the pressure fluctuation in the turbine draft tube effectively. With the increase of the jet flow rate, a greater reduction of pressure fluctuation magnitude was detected, but a decrease of efficiency was found. To keep a balance between pressure fluctuation mitigation and efficiency requirement, 0.03~0.05 times of flow rate at the calculated operating condition was suggested.