By Etienne Parkinson| VA TECH HYDRO Ltd. 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