Abstract
Three-dimensional unsteady turbulent flow through the entire flow passage of a model Francis hydraulic turbine is simulated using the transition shear-stress transport turbulence model and verified with experimental data. Pressure oscillations with the original runner cone, an extended runner cone, an extended runner cone with grooves, and a round-top runner cone are analysed under five operating conditions. The computational results show that (1) runner cone design can change the distribution pattern of the vortex rope in the draft tube and narrow the zone of special pressure oscillation; (2) the dominant frequency of pressure oscillation in the draft tube at guide vane opening angle,
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