A Turgo turbine system comprises a penstock, nozzle and turbine disc or wheel. The Turgo turbine model is required give a robust and computationally simple first approximation of per- formance characteristics and to identify the critical parameters to be experimentally controlled. Fig. 2b shows a general dia- gram for the interaction between the water jet and a set of Turgo turbine cups, with Fig. 3a and b showing the velocity diagrams. The following simplifying assumptions are made: