Thanks to developments in simulation methods over the last twenty years, the optimization of the hydraulic design of reaction-type water turbines (Francis and Kaplan turbines) is now primarily carried out by means of numerical flow simulation. In the design process, numerical flow simulation provides the engineer with a rapid and reliable tool to obtain a better understanding of the flow and to quickly examine various design options in order to select the optimum configuration.

A similar move towards the use of simulation methods is now taking place in the field of Pelton turbines. Until now, the flow in Pelton turbines has not been analyzed in such detail as the flow in Francis and Kaplan turbines. One of the reasons for this is that the flow patterns and the hydraulic losses are very difficult to observe and quantify by experiments. This is due to the very complex flow processes that occur in Pelton turbines, which include pressure losses, secondary flows, jets, film flow, free surfaces, spray formation, ventilation losses, unsteadiness, and complex interaction between the components.