Numerical Simulation of Low Specific Speed Pelton Turbines: Challenges and Evaluation

This study presents a numerical analysis of a low-specific-speed Pelton turbine using the open-source Lagrangian code DualSPHysics. The numerical results were compared with experimental data. The main objective was to determine whether the applied numerical approach yielded reproducible results and provided insight into momentum transfer and water movement in the jet, runner, and casing. The influence of numerical parameters, such as particle size, kernel and smoothing length coefficients, and shifting value, on the simulation results was tested. As a result, an optimal particle size formulation is suggested. Furthermore, we established connections for two numerical parameters in DualSPHysics, the “smoothing length coefficient” and the “shifting”, to improve fluid flow behaviour and the resulting torque without modifying the physical parameters. In addition, we investigated deviations from the optimal achievable torque and improvements in fluid behaviour using these numerical parameters. We discussed the effect of the bucket disturbance on the jet from the particle simulation, alongside the similarity law simulation and the actual prototype’s measurement results. Identical simulations of the physical properties of the operation points were compared in momentum.